Anatomy Flashcards

Question

Vesibular nuclei projections within the brainstem (3)

Answer 1

Vestibular nuclei and ganglia --\> caudal cerebellar peduncle --\> cerebellum * Cortex of the flocculus of the hemisphere * Nodulus of the vermis * Fastigal nucleus \*\* projections from the vestibular nuclei to and from the cerebellum are ipsilateral (this is unique among extrapyramidal centers) --\> correlate this with the fact that the vestibulospinal tract does NOT decussate

Answer 2

Quick phase of the nystagmus is directed opposite the direction of rotation Caloric nystagmus - normally induces a jerk nystagmus to the side opposite the ear being stimulated

Answer 3

Ablation of the fastigal nucleus --\> inhibition of the ipsilateral vestibular nuclei --\> vestibular signs Spinal nerve dorsal roots or dorsal gray matter of the first 3 cervical spinal cord segments interrupted --\> ipsilateral vestibular dysfunction Spinal cord lesions that interrupt the spinovestibular tracts may have the same effect

Answer 4

First 1-2 cervical vertebrae, and to the atlantooccipital membrane The terminal branches of the vertebral arteries pass through the **lateral vertebral foramina** to enter the vertebral canal at the atlas, then join the ventral spinal artery to form the basilar artery Internal carotid arteries: enter the carotid canal at the tympanic part of the temporal bone --\> foramen lacerum --\> tympanooccipital fissure --\> through cavernous venous sinus \*\* between the hypophysis and optic chiasm, the internal carotid artery emerges through the dura --\> rostral cerebral, middle cerebral, caudal communicating arteries

Answer 5

Rostral cerebral arteries --\> course dorsally between the 2 frontal lobes in the longitudinal cerebral fissure --\> dorsally over the genu of the corpus callosum to supply the rostral gyri on the medial cerebral hemisphere \*\* terminal branches anastamose with branches of the middle cerebral artery on the dorsomedial cortex

Answer 6

Rostral hypophysis: Courses laterally, rostral to the piriform lobe --\> dorsolateral over the surface of the cerebral hemisphere --\> branches supply the entire lateral hemisphere * Terminal branches anastamose with those of the rostral and caudal cerebral arteries along the dorsomedial gyri of the cerebral hemisphere * **Rostral choroidal artery** - arises at the origin of the middle cerebral artery --\> medial surface of the piriform lobe --\> ventro-rostral hippocampus --\> **choroid plexus** of the lateral ventricle * **Striate branches** - supply the **basal nuclei**, rostral thalamus, white matter tracts within the cerebral hemisphere (internal capsule)

Answer 7

Leave the circle at the caudal hypophysis (rostral to the oculomotor nerve) * Courses caudo-dorso-medially following the **optic tract** to the longitudinal cerebral fissure * Continues rostrally on the caudal aspect of the **corpus callosum** * Branches anastamose with the rostral and middle cerebral arteries medially * Supplies the **caudal cerebral hemisphere, diencephalon, rostral mesencephalon**

Answer 8

Rostral cerebellar artery * Leaves the caudal communicating artery of the arterial circle caudal to the oculomotor nerve * Course dorsocaudally along the pons and middle cerebellar peduncle to the cerebellar hemisphere * Supplies the caudal midbrain and rostral half of the cerebellum * Branches: medial, lateral, intermediate

Answer 9

At the level of the rostral border of the transverse fibers of the pons Caudal cerebellar artery * Branch of the basilar artery near the middle of the medulla * Courses dorsally to supply the caudal portion of the cerebellum Labyrinthe artery * Branches from the basilar artery and follows the vestibulocochlear nerve through the internal acoustic meatus adjacent to the inner ear Basilar medullary and pontine branches penetrate the adjacent parenchyma

Answer 10

1. Maxillary 2. internal jugular 3. vertebral veins 4. Ventral internal vertebral venous plexus Enteres the foramen for the dorsal sagittal sinus in the occipital bone, then: * Joins the left and right transverse sinuses at the confluens of the sinuses The dorsal sagittal sinus receives branches from the dorsal surface of each hemisphere and many of the diploic veins ROSTRALLY it is formed by the right and left veins of the nasal cavity

Answer 11

Great cerebral vein + vein of the corpus callosum forms the straight sinus It drains into the dorsal sagittal sinus (either before or after the foramen) Transverse sinus: runs through the transverse canal and sulcus Divides into a temporal sinus and sigmoid sinus

Answer 12

Temporal sinus - leaves @ the retroarticular foramen within the petrosal bone --\> "emissary vein of the retroarticular foramen" --\> maxillary vein Sigmoid sinus - leaves @ jugular foramen, then TOF --\> joins ventral petrosal sinus --\> vertebral and internal jugular veins Transverse sinus --\> temporal sinus and sigmoid sinus

Answer 13

Vertebral vein descends the neck in the transverse foramen of the cervical vertebrae Basilar sinus is a branch of the sigmoid sinus --\> condyloid canal --\> ventral internal vertebral venous plexus in the vertebral canal

Answer 14

Rostral: orbital fissure. Caudal: petrooccipital canal Connects with ophthalmic plexus rostrally and maxillary veins laterally Drains causally to the ventral petrosal sinus --\> sigmoid sinus --\> basilar sinus 2-3 intercavernous sinuses run between the right and left cavernous sinuses

Answer 15

Vertebral veins of the neck Intercostal veins of the thorax --\> azygous and costocervical veins Lumbar veins --\> caudal vena cava

Answer 16

Rostral to the cruciate sulcus * The precruciate gyrus is part of this lobe - functions in motor cortex Parietal lobe - caudal to the cruciate sulcus, dorsal to the sylvian gyrus, (no defined caudal boundary, extends causally to the caudal 1/3 of the cerebral hemisphere) * Postcruciate and rostral suprasylvian gyri found in this lobe Occipital lobe - caudal 1/3 of cerebral hemispheres Temporal cortex - sylvian gyri function as the auditory ad vestibular system cortex

Answer 17

Rhinal sulcus

Answer 18

Choroid plexus develops where the neural tube neuroepithelium did not proliferate to form neuroparenchyma but remained as a single layer of ependymal neuroepithelial cells = roof plate The layer of ependymal neuroepithelial cells and the adjacent pia = tela choroidea Associaed proliferation of capillaries = choroid plexus Roof plate of the medulla = choroid plexus in the 4th ventricle Roof plate of the diencephalon = choroid plexus of the 3rd ventricle Roof plate of the telencephalon = choroid plexus of the lateral ventricles

Answer 19

2 geniculate bodies * located lateral and dorsocaudal to the thalamus Lateral geniculate connects to the rostral colliculus via brachium Medial geniculate connects to the caudal colliculus via brachium

Answer 20

Stria habenularis - lies on either side of midline, courses dorsally and caudally from the rostroventral aspect of the hypothalamus over the thalamus to the dorsocaudal aspect of the diencephalon and enters the habenular nucleus * Considered part of the EPITHALAMUS There is a thin remnant of the roof plate of the neural tube that extends from one stria habenularis to the other, covered by a thin layer of pia mater

Answer 21

Subarachnoid space dorsal to the mesencephalon @ the level of the mesencephalic aqueduct Single, unpaired

Answer 22

Middle cerebellar peduncle = most lateral Caudal cerebellar peduncle = Medial and caudal Rostral cerebellar peduncle = most medial and rostral 12: rostral 11: caudal 10 : middle

Answer 23

Dorsal aspect of the thalamus, adjacent to the third ventricle, at the level of the interthalamic adhesion and pituitary gland

Answer 24

CB1 receptor found in the dorsal horn * CB1 receptors inhibit voltage-gated calcium channels, decrease excitatory acetylcholine neurotransmitters, increase GABA neurotransmission CB2 receptors found primarily in immune cells * Activation of CB2R receptors do not cause the effects on mentation that activation of CB1R produces - has become a target for therapeutic use in human medicine by reducing inflammation, immune suppression, and as chemotherapeutic (ACVIM 2017)

Answer 25

A pressure fluctuation of 1-2mmH20 is normally associated with arterial pulse in humans Inspiration --\> fall in CSF pressure (the amplitude is extremely variable) In pathological ICP elevations - these fluctuations in CSF pressure become very marked If there is a sudden increase in intracranial blood volume, CSF can be momentarily accommodated into the cervical subarachnoid space (DeTerlizzi)

Answer 26

True The CSF is a vehicle for the intracerebral transport of biologically active substances Intracerebral transport of opioids and other neuroactive substances from systemic circulation occurs as well (DeTerlizzi)

Answer 27

1. Rostral horn 2. Temporal horn Subarachnoid space Also median aperture (obex) opens into subarachnoid space, unclear if this is present in the dog? (DeTerlizzi)

Answer 28

1. Blood brain barrier 2. Blood CSF barrier 3. CSF brain barrier (DeTerlizzi)

Answer 29

Area postrema * Anatomically positioned to detect toxins in the blood and CSF * Helps monitor and control changes in body fluid compositions such as: * Plasma osmolality * Glucose concentration * Electrolyte concentration (DeTerlizzi)

Answer 30

Cochlear aqueduct, lies between scala tympani and the subarachnoid space

Answer 31

1. Zona occludens associated proteins 2. Cingulin (DeTerlizzi)

Answer 32

* Highly permeable * Water * CO2 * Oxygen * Most lipid-soluble substances (alcohol, anesthetics) * Slightly permeable * Sodium * Chloride * Potassium * Impermeable * Plasma proteins * Non-lipid soluble large organic molecules

Answer 33

1. Endothelial cells - nonfenestrated with interendothelial tight junctions 2. Pericytes - located in basement membrane sheath 3. Perivascular macrophages 4. Astrocyte foot processes (Boron)

Answer 34

Proliferation of ectodermal epithelial cells called the neuroectoderm The neural plate is formed from thickened ecroderm * Invaginates along its axis forming a groove, until the lateral extremities of the plate (also called neural fold) fuse --\> neural tube and canal * As the neural tube forms, it separates from the nonneural ectoderm Nonneural ectoderm grows over the dorsum of the tube and fuses along midline (DeLahunta)

Answer 35

Arise from the junction of the nonneural and neural ectoderm As the neural tube forms, it separates from the non-neural ectoderm dorsally As this separation occurs, a longitudinal column of neural crest cells is left behind in 2 longitudinal columns The neural crest cells are situated in 2 bilateral columns dorsolateral to the neural tube (DeLahunta)

Answer 36

Progresses rostrally and caudally from the site of development of the rhombencephalon Closure of the brain portion occurs initially at multiple sites - locations of these sites vary among species of animals Before complete closure, the most rostral opening = rostral neuropore (DeLahunta)

Answer 37

1. Prosencephalon 2. Mesencephalon 3. Rhombencephalon

Answer 38

1. Optic vesicles - grow laterally to contact the overlying skin ectoderm 2. Telencephalic vesicles - emerge from rostral prosencephalon, grow out of the neural tube laterally and dorsally * These vesicles overgrown the original vesicular system, form the cerebral hemispheres Diencephalon = portion of the prosencephalon that remains at the rostral end of the neural tube * The optic vesicles remain associated with the diencephalon (DeLahunta)

Answer 39

Diencephalon (de Lahunta)

Answer 40

Dorsal metencephalon = cerebellum Ventral metencephalon = pons Caudal rhombencephalon = myelencephalon = medulla oblongata Lumen of the neural canal in the rhombencephalon --\> 4th ventricle (de Lahunta)

Answer 41

During interphase, nuclei are located on the external surface of the neural tube As the nucleus enters mitosis, it migrates through the cytoplasm to the luminal surface of the neural canal The peripheral portion of the cytoplasm and cell membrane retract to the new luminal position, where cell division is completed The 2 new daughter cells extend their cytoplasm and cell membranes back to the external surface of the neural tube, and the nuclei migrate back to the periphery again * Once in this position, the cells may undergo another mitosis or may differentiate * Because the nucleus is at the EXTERNAL surface during interphase, differentiation occurs at the EXTERNAL surface (de Lahunta)

Answer 42

1. Neuroblasts * Immature neurons * They will not divide again * Grows extensively, forms long processes to become a mature functioning cell 2. Spongioblasts * Form astrocytes and oligodendroglia As immature neurons and spongioblasts are differentiated and grow, and the neurons produce processes, the neural tube becomes arranged in 3 concentric layers 1. Germinal layer 2. Mantle layer 3. Marginal layer (de Lahunta)

Answer 43

1. Germinal layer * Layer adjacent to the neural tube * Proliferating neuroepithelial cells - mitotic activity is eventually exhausted, reducing the germinal layer to single layer of ependymal cells 2. Mantle layer * Initially consists of immature neurons and spongioblasts * Ultimately becomes the gray matter of the spinal cord, brainstem nuclei, cerebellum (nuclei and cortex), and cerebral cortex/basal nuclei 3. Marginal layer * Initially growing axonal processes of the neuronal cell bodies in the mantle layer * Axons become myelinated by oligodendroglial cells - form the tracts in the white matter (de Lahunta)

Answer 44

Sulcus limitans * Divides the neural tube into dorsal and ventral portions * Dorsal part = alar plate = sensory * Ventral part = basal plate = motor * Floor plate - connects the sides ventrally

Answer 45

Radial glia * The undergo postnatal differentiation with immature neurons, astrocytes, oligodendrocytes, and ependymal cells * After development is completed, they populate the: * Subventricular zone - lateral ventricles of the frontal lobe * Subgranular zone of the hippocampal dentate gyrus (de Lahunta)

Answer 46

Subventricular zone - most evident in association with the lateral ventricle of the frontal lobe (de Lahunta)

Answer 47

Replaces the dentate gyrus granule neurons (de Lahunta)

Answer 48

1. Surface ectoderm (adjacent to the ectoderm that formed the neural plate) * Secretes bone morphogenic protein 4 (BMP4) = cytokine that enters the neural tube and directs the development of the dorsal portion of the neural tube * Triggers the release of transforming growth factor beta - diffuses ventrally in the neural tube to induce formation of dorsal horn neurons 2. Notocord (located ventral to the neural tube) * Secretes sonic hedgehog signaling molecule * Diffuses dorsally in the neural tube - induces formation of ventral horn neurons (de Lahunta)

Answer 49

Ventral growth of the 2 basal layers and associated marginal layers beyond the level of the floor plate GVA/GVE - located adjacent to each other in their respective dorsal and ventral horns on either side of the dorsal plane through the sulcus limitans GSA and GP neuronal columns - located dorsally in the mantle layer of the alar plate GSE - located ventrally in the mantle layer of the basal plate (de Lahunta)

Answer 50

Neural crest cells (de Lahunta)

Answer 51

1. Melanoblasts to the somitic dermatome and adjacent epidermis 2. Cell bodies of post-ganglionic axons in the 2 neuron GVE system 3. Medullary cells of the adrenal glands 4. Glial cells in the wall of the bowel (plus GVE neurons create enteric nervous system) 5. Contributes to formation of the bone and cartilage of the skull 6. Derivatives of the brachial arches 7. Walls of the great vessels at the base of the heart 8. Thyroid parafollicular cells 9. Odnotoblasts 10. Meninges 11. Lemmocytes (Schwann cells) that form myelin of PNS (de Lahunta)

Answer 52

Hox genes * Similar to spinal cord, prechordal plate and rostral ventral notochord --\> secrete SHH --\> influences ventral patterning of the brain * BMP 4 and 7 secreted by surface ectoderm - control dorsal patterning of the brain (de Lahunta)

Answer 53

The dorsal roof plate of the neural tube is stretched extensively dorsolaterally instead of being obliterated by the proliferating alar plate and marginal tissue This displaces the alar and basal plates into a lateral and ventral position and enlarges the lumen of the neural tube to form the 4th ventricle The 4th ventricle is covered dorsally by a single layer of neuroepithelial cells that become ependymal cells Sulcus limitans present in the ventrolateral wall of the 4th ventricle provides the plane of division of the medulla into a ventromedial basal plate and dorsolateral alar plate (de Lahunta)

Answer 54

CN VII, IX, X, and XI The GSE neurons of the facial nerve migrate from their initial formation in the mantle layer --\> facial nucleus in a ventrolateral position * This migration is called neurobiotaxis * As s result of this migration, the axons leaving this facial nucleus initially course dorsomedially to the floor of the 4th ventricle, before turning to course ventrolaterally to leave the medulla and form the facial nerve GSE cell bodies of 9, 10 and 11 undergo a migration ventrolaterally - form the nucleus ambiguus (de Lahunta)

Answer 55

Just ventromedial to the sulcus limitans Their axons leave in cranial nerves 7, 9, 10 and 11

Answer 56

1. Neural crest cells * Sensory ganglia of 7, 9, and 10 (GVE and SVA functions) 2. Brachial arch ectoderm - ectodermal cells that proliferate to form cranial placodes * Sensory ganglia of 8 (Special proprioception for vestibular, special somatic afferent for auditory) (de Lahunta)

Answer 57

1. Neural crest cells 2. Mesodermal cells (de Lahunta)

Answer 58

The roof plate of ependymal cells and the thin layer of vascularized pia associated with it Capillaries here proliferate to form 2 longitudinal rows of a dense capillary bed (de Lahunta)

Answer 59

Medullary roof plate Here, the choroid plexus protrudes from the lumen of the 4th ventricle out through the aperture @ each side of the cerebellomedullary angle (de Lahunta)

Answer 60

Motor neurons arise in the basal plate of the mantle layer --\> migrate ventrolaterally into the parenchyma of the pons --\> small, well-defined motor nucleus The GSE of CN V innervate the muscles of mastication derived from the somitomeres of brachial arch 1 Dendritic zones of the head/mucosa --\> sensory neurons derived from **neural crest cells** that form the trigeminal ganglion (GSA neurons) --\> trigeminal ganglion GP neurons for the muscles/joints of the head region --\> pons These sensory axons enter the alar plate region --\> for the spinal tract of the trigeminal nerve in the pons/medulla/cranial cervical spinal cord --\> terminate in telodendria at synapses in the alar plate (forms sensory pontine nucleus of the trigeminal nerve (in the pons) and the nucleus of the spinal tract of the trigeminal nerve (in the medulla and cranial spinal cord)) \*\* caudally the spinal tract and nucleus meet the analogous functional neurons in the first cervical spinal nerves and spinal cord segment (de Lahunta)

Answer 61

The germinal epithelial cells of the alar plate (forming the rhombic lip) This growth dorsolaterally from each site replaces the roof plate of the 4th ventricle, so that the cerebellum forms part of the dorsal boundary of the 4th ventricle in the metencephalon (de Lahunta)

Answer 62

Ventral migration of alar plate mantle neurons forms both nuclei Pontine - Axons of these neurons cross midline and course dorsally into the cerebellum = transverse fibers of the pons --\> middle cerebellar peduncle

Answer 63

Basal plate mantle layer GSE of III and IV - cell bodies do not migrate, remain adjacent to the median plate ventral to the mesencephalic aqueduct The parasympathetic nucleus of CN III is rostral to the GSE nucleus - neurons also derived from basal plate mantle layer (de Lahunta)

Answer 64

Alar plate proliferates dorsally to form the tectum of the midbrain - divides into paired rostral and caudal colliculi - associated with afferent visual and auditory reflex functions The crus cerebri results from telecephalic projection neurons growing causally (de Lahunta)

Answer 65

Rostral to the mesenceephalon Diencephalon + telencephalon - alar plate (de Lahunta)

Answer 66

Dorsal median plane of the diencephalon, proliferation of the neural tube epithelial cells does not occur, leaves a single cell thick roof plate * Small choroid plexus develops in 2 parallel lines * At the interventricular foramina, each of these is continuous with the choroid plexus that develops from the roof plate of each lateral ventricle (de Lahunta)

Answer 67

Neurohypophysis - forms from the subthalamus Adenohypophysis - Dorsal extension of adjacent oral ectoderm (hypophyseal-rathke pouch)

Answer 68

Collection of axons outside the CNS that are myelinated by Schwann cells and arise from the NEURAL CREST CN 2 axons are myelinated by CNS oligodendroglial cells, covered by meninges, and bathed in CSF (de Lahunta)

Answer 69

Lamina terminalis of the diencephalon This is the rostral boundary of the third ventricle The optic chiasm is located at the ventral portion of this lamina The **rostral commissure** develops (and remains in) this lamina (de Lahunta)

Answer 70

Rostral commissure The lamina terminalis is located on the median plane between these 2 outgrowths Each telencephalic vesicle grows out of the prosencephalon a short distance rostrally, and then in a large curve caudally and ventrally Each telencephalon forms a cerebral hemisphere connected by the corpus callosum (de Lahunta)

Answer 71

At one aspect of the **medial wall** wall of the telencephalic vesicle, the neuroepithelial layer of the neural tube does not proliferate and remains a single layer of cells that become ependymal cells * Comparable with the roof plate of the myelencephalon (dorsal to the 4th ventricle) and roof plate of the diencephalon (dorsal to the 3rd ventricle) This telencephalic roof plate will be attached to the crus of the hippocampal fornix on each side of the stria terminalis The choroid plexus of each lateral ventricle develops here (de Lahunta)

Answer 72

1. Paleopallium (olfactory system) * Olfactory bulbs * Olfactory peduncles * Piriform lobe cortex 2. Archipallium * Hippocampus 3. Neopallium * Cerebral surface (de Lahunta)

Answer 73

* Association: course between cortical areas within 1 cerebral hemisphere * Projection: leave the cerebral hemisphere where their cell bodies are located and enter the brainstem via the internal capsule * Commissural: cross from one cerebrum to the other (de Lahunta)

Answer 74

All initially develop in the lamina terminalis 1. Rostral commissure - located ventrally in the lamina terminalis * Course primarily between paleopallial structures (olfactory) and the basal nuclei on each side 2. Hippocampal commissure * Migrated caudodorsally as the telencephalon developed to reach a position dorsal/caudal to each diencephalon * Courses between each archipallium (hippocampus) 3. Corpus callosum * Expands dorsally as the cerebrum develops so that it is positioned between the other 2 commissures * Conects neopallial areas of each hemisphere * Begins in the lamina terminalis, as telencephalic vesicle expands, corpus callosum enlarges and extends causally and dorsal to the diencephalon * Cingulate gyrus is located dorsal * Hippocampus and body of the fornix are ventral * Forms the lateral roof of the lateral ventricle * Septum pellucidum develops dorsally in the lamina terminalis between the genu of the corpus callosum and rostral body of the fornix

Answer 75

Mantle and marginal layers reverse their positions * Axons of the mantle layer migrate while axons grow centrally - results in gray matter on the surface and white matter centrally * Radial astrocytes participate in this migration - guide neurons to the surface of the neural tube Except for the basal nuclei - they are formed by neurons that migrate only a short distance from the mantle layer into the developing white matter

Answer 76

Layer VI (deepest) As more neurons arrive, they pass those already there to form the rest of the layers in a reverse sequence The last neurons to arrive form layer I (mot superficial) (de Lahunta)

Answer 77

Olfactory system and hippocampus (de Lahunta)

Answer 78

Arachnoid cap cells which arise from neural crest cells (de Lahunta)

Answer 79

GLUT 1 - located on luminal side and basolateral side (Boron)

Answer 80

1. Vascular endothelium * Leaky capillaries * These are OUTSIDE the BBB 2. Choroidal epithelium * Specialized ependymal cells * Tall columnar epithelial cells with microvilli brush border and cilia * APICAL TIGHT JUNCTIONS - different than BBB where the endothelium has tight junctions

Answer 81

Sympathetic input --\> decreases CSF production (vasoconstriction?) Plasma hypoosmolality --\> increase CSF formation Plasma hyperosmolality --\> decrease CSF formation Linear relationship Blood flow to the choroid plexus is via the anterior/posterior choroidal artery The blood flow to the choroid plexus is 10x greater than the average cerebral blood flow (Boron)

Answer 82

The extracellular space of the median eminence is exposed to substances in the blood (which can modulate the release of hypothalamic releasing factors) The ependymal layer over the hypothalamic region of the 3rd ventricle has TIGHT JUNCTIONS that limit the movement of substances between the hypothalamic nuclei and the CSF (Boron)

Answer 83

Villi = microscopic (Very tiny); granulations = up to 1cm (giant) 2 routes of CSF absorption: 1. Arachnoid villi 2. Lymphatics associated with spinal nerves 3. (also drains across the arachnoid at cranial nerves - considerably drainage at CN 1 and 2)

Answer 84

Arachnoid villi are projections of arachnoid membrane (deep) into dural venous sinuses (dorsal) \*\* also found in veins at intervertebral foraminae * At a villus, cerebrospinal fluid is separated from blood by flattened fibroblasts and endothelial cells * Each villus functions as a valve, regulating flow CSF into the venous sinus * CSF pressure exceeds venous pressure --\> villi expands and spaces between cell processes increase - more fluid can flow from the subarachnoid space to the venous sinus * When pressure in the sinus exceeds CSF pressure, villi collapse * May also involve transcytosis (de Lahunta)

Answer 85

True - Ependyma and pia are highly permeable Choroid plexus weight and exchange of Na/HCO3-

Answer 86

1. Ependymal lining of the ventricles 2. Pia/arachnoid vessels in the subarachnoid space 3. Pial-glial membrane CSF: ultrafiltrate of plasma, then active secretion of SODIUM results in formation * Active transport of Na into the ventricle * Na/K ATPase * Water, Cl, and HCO3 follow by "facilitated transport" * Carbonic anhydrase involved

Answer 87

Cl, magnesium, sodium - slightly higher in CSF vs. plasma Ca, K+, and glucose - slightly lower in CSF vs. plasma Protein - significantly lower in CSF than plasma (De Terlizzi)

Answer 88

Enters via: * Facilitated transport * Diffusion Dependent on * Blood glucose concentration * If BG is low, glucose is more avidly transported across the CNS capillary via carrier mechanism * Rate of glucose transport into the CSF * Metabolic rate of thee CNS * (NOT dependent on insulin) (De Terlizzi)

Answer 89

Acetazolamide = carbonic anhydrase inhibitor - slows entrance of sodium into the CSF Vasopresin - enhances movement of sodium from blood to brain (De Terlizzi)

Answer 90

Plasma concentration has little effect on K+ concentration Even with very high K+ plasma concentrations, the CSF potassium concentration remains within the normal range Choroid plexus epithelium has a lower permeability to K+ than to sodium (reverse is true at capillaries) If K+ is increased in the CSF, it is exchanged for Na to reduce K and increase Na (De Terlizzi)

Answer 91

Active transport mechanism at the BBB Active transport at the vascular endothelium Active transport at the choroid plexus epithelium (De Terlizzi)

Answer 92

They are independent * The CSF brain has its own isozyme of CK Extensive myelin degradation Also inflammation of the CSF often associated with increased LDH activity (De Terlizzi)

Answer 93

Study demonstrated decreased activity of CSF enzymes after subarachnoid hemorrhage in dogs Changes in CSF lactate and pyruvate - may indicate mitochondrial disease (De Terlizzi)

Answer 94

GABA - low levels found in CSF of dogs with epilepsy Glutamate - Elevated in epilepsy (and other diseases) Dogs \< 170 mmH2O; Cats \< 100mmH2O Vitamin A deficiency --\> arachnoid vili atrophy --\> poor absorption (De Terlizzi)

Answer 95

0.75 - 2mL CSF has low protein, lipid, and tonicity (De Terlizzi)

Answer 96

1. Nuclear pyknosis 2. Lysis 3. Disintegration of the cytoplasmic and nuclear membranes Neutrophils degenerate within 1 hour, lymphocytes and macrophages after 3 hours Eosinophils seem most stable (De Terlizzi)

Answer 97

Addition of fetal calf serum with a protein concentration of 3.7g/dL to CSF at a concentration of 20% volume Addition of hetastarch to CSF at a ratio of 1:1 Calf serum appears to stabilize mononuclear cells more effectively than hetastarch Addition of 1 drop of 15% formalin to 1-2mL CSF may be used to preserve cell concentration and structure for up to 8h after collection (De Terlizzi)

Answer 98

Basisphenoid bone Rostral margin = rostral clinoid process Caudal margin = dorsum sella (Big Miller)

Answer 99

Sella turcica is lined by external/endosteal layer of dura The inner layer of dura forms the diaphragm sellae that attaches to the clinoid process and does not extend fully into the hypophyseal fossa, has a oval slip that the infundibulum passes through The subarachnoid space does not invest the hypophysis (Big Miller)

Answer 100

The cavernous sinuses bind the hypophysis laterally, connected by intercavernous sinuses Larger intercavernous sinus passes caudal to the hypophysis Some individuals have a smaller intercavernous sinus that passes rostral to the hypophysis (Big Miller)

Answer 101

Caudal aspect of the hypophysis Caudal part of the arterial circle is found here (Big Miller)

Answer 102

Large compressed vesicle that is a remnant of the development of the stomodeal adenohypopseal sac (Big Miller)

Answer 103

Pars intermedia: between the neural lobe and adenohypophysis Pars distalis: separated from the pars intermedia by the hypophyseal cavity Pars tuberalis: extends as a cuff around the infundibulum to envelop part of the tuber cinereum (Big Miller)

Answer 104

Acidophilic endocrine cells * Smaller than basophilic cells * Arranged around sinusoids * 2 types - cells that produce somatotropin and cells that produce lactotrophin Basophilic endocrine cells * Cytoplasmic granules that have moderate affinity for basic component dye * Granules composed of glycoprotein * Larger than acidophilic cells * Produce thyrotropin and gonadotrophins Chromophobic cells * Moderate numbers in the central region * Produce adrenocorticotropin (Big Miller)

Answer 105

Melanocyte-stimulating hormone Adrenocorticotropin (Big Miller)

Answer 106

Neurons with cell bodies in the hypothalamus --\> axons pass to the neural lobe via the infundibulum Glial cells = pituicytes are the cells that support the axons The axons release vasopressin and oxytocin at their synapse (Big Miller)

Answer 107

Main arterial sources: internal cartotid arteries + caudal communicating arteries There are also branches from the rostral intercarotid artery, and branches from the rostral communicating arteries These arteries form the "mantle plexus" that is within the meninges (Big Miller)

Answer 108

Mantle plexus --\> rostral hypophyseal arteries --\> capillaries to the tuber cinereum and proximal infundibulum --\> primary blood capillary network \*\* The primary blood capillary network receives neurohormonal secretions called releasing factors from the median eminence --\> takes them to the hypophysis The capillaries of the adenohypophysis form the secondary blood capillary network Hypophyseal portal vessels = veins that connect the primary and secondary capillary network (Big Miller)

Answer 109

Neurohypophysis Cavernous and intercavernous sinuses (Big Miller)

Answer 110

Supraoptic nuclei --\> supraopticohypophyseal tract Paraventricular nuclei --\> paraventriculohypophyseal tract They are UNMYELINATED axons Sympathetic axons from the cranial cervical ganglion pass via tunica externa of the internal carotid artery and its branches to the vessels of the hypophysis Parasympathetic innervation has not been described It is believed that the hormonal input from the adenohypophysis is not under direct autonomic control (Big Miller)

Answer 111

Medial gray horn --\> axial muscles Lateral gray horn --\> appendicular muscles * The PROXIMAL limb muscles are located in the --\> ventrolateral ventral gray horn * DISTAL limb muscles --\> dorsal VGH (de Lahunta)

Answer 112

Fibular nerve: L6 and L7 Tibial nerve: L7 and S1 (deLahunta)

Answer 113

All species have 7 cervical vertebrae Ox: T13, L6, S5 (ends @ L6/S1) Horse: T18, L6, S5 (ends @ S2) Sheep: T13, L6-7, S4 (ends @ L6-S1) Swine: T14-15, L6-7, S4 (ends @ S1-2) (de Lahunta)

Answer 114

Withdrawal: * All thoracic limb nerves * Spinal cord segments C6-T2 / C5-T1 within the vertebral canal Biceps: * Musculocutaneous * Spinal cord segments C6-8 / C5-7 within the vertebral canal Triceps: * Radial nerve * Spinal cord segments C7-T2 / C6-T1 within the vertebral canal Extensor carpi radialis: * Radial nerve * Spinal cord segments C7-T2 / C6-T1 within the vertebral canal (de Lahunta)

Answer 115

Withdrawal: * Sciatic nerve * Spinal cord segments L6-S1 / located @ L4-5 within the vertebral canal Patellar * Femoral nerve * Spinal cord segments L4-6 / located @ L3-4 within the vertebral canal Cranial Crural * Fibular nerve * Spinal cord segments L6-7 / located @ L4 within the vertebral canal Gastrocnemius * Tibial nerve * Spinal cord segments L7-S1 / located @ L4-5 within the vertebral canal (de Lahunta)

Answer 116

Rectus femoris Digit 1 (Medial) - saphenous nerve branch of the femoral nerve Digit V (Lateral) - sciatic \*\* as a rule, with a partially compressed nerve, there will be more loss of motor function with some preservation of sensory function (de Lahunta)

Answer 117

Pinch the skin of the perineum/anus (supplied by the superficial perineal nerve, branch of the pudendal nerve) --\> S1-3 (located @ L5/6) --\> * Caudal nerves --\> ventral caudal plexus --\> sacrocaudalis ventralis lateralis (long depressor of the tail) - flexes the tail * --\> caudal rectal nerve --\> external anal sphincter (Big Miller)

Answer 118

Femoral nerve: * L4, 5, 6 * Iliopsoas, quadriceps, sartorius * Iliopsoas: flex hip (lumbar hypaxial m) * Quadriceps: extend stifle joint, flex hip (cranial thigh) * Sartorius - cranial part - hip flexion, caudal part - stifle extension (medial thigh) (Big Miller)

Answer 119

* L4, 5 (6) * External obturator, pectineus, gracilis, adductor * Overall: Adduction of the limb, extension/lateral rotation of the hip joint, flexion of the stifle, extension of the tarsus * Located caudal thigh region (obturator is considered pelvic muscle) * Courses on the medial surface of the ilium, is at risk for injury by iliac fractures * PL will slide out (Big Miller)

Answer 120

* L6, 7, S1 * Middle gluteal, deep gluteal, tensor fascia lata * Lateral pelvic muscles * TFL - flex hip, abduct limb * Middle/deep gluteal - extend hip, medial rotation of the hip (Big Miller)

Answer 121

Caudal gluteal: * L7, (S1, 2) * Superficial gluteal, (middle gluteal) * Lateral pelvic muscles - Extends the hip (Big Miller)

Answer 122

Sciatic nerve * L6-S1 (S2) * Biceps femoris, Semimembranosus, Semitendinosus (caudal muscles of the thigh) * Action: Hip extension, stifle flexion, tarsus extension (Big Miller)

Answer 123

Common fibular nerve * L6, 7 * Fibularis longus, lateral digital extensor, long digital extensor, cranial tibial * Craniolateral muscles of the crus * Tarsus flexion, digit extension, rotation of the hind paw medially (Big Miller)

Answer 124

Tibial: * L7, S1 * Muscles: Gastrocnemius, popliteus, superficial digital flexor, deep digital flexor * Caudal muscles of the crus * Action: Extends tarsal joint, flexion of stifle joint Plantigrade --\> TIBIAL NERVE (Big Miller)

Answer 125

Sensory stimulus: mild compression of the skin alongside the spinous processes of the vertebrae using forceps --\> Doral roots --\> dorsal gray column --\> synapses on long interneurons --\> fasiculus proprius on both sides --\> project in the ipsilateral and contralateral fasiculus proprios on both sides Interneurons project cranially to C8/T1 --\> ventral gray column --\> GSE LMN of the lateral thoracic nerve

Answer 126

Septum = thin barrier, formed principally by astrocytes in white matter Sulcus is a shallow grove on the spinal cord surface Fissure = midline cleft typically lined by pia mater From large to small: Fissure \> sulcus \> septum Dorsal median fissure - absent in cervical and thoracic segments (there is a sulcus and septum instead), present in lumbar Dorsal intermediate sulcus: cervical spinal cord (Big Miller)

Answer 127

1cm caudal to the last segment of the spinal cord, the spinal cord is reduced to a uniform strand of glial and ependymal cells called the **filum terminale**. Encased in a layer of **pia mater.** * A caudal extension of dura mater that envelops the filum terminale is called the spinal dura mater filament - extends causally in the vertebral canal and attaches to a sacral or caudal vertebrae * A dura-arachnoid sac enclosing subarachnoid space and CSF in a lumbar cistern, extends approximately 2cm caudal to the end of the spinal cord neuroparenchyma (Big Miller)

Answer 128

1. Alpha motor neurons 1. Innervate typical muscle fibers responsible for producing muscle tension 2. Gamma motor neurons * Aka fusimotor neurons * Innervate intrafusal muscle fibers within muscle spindles 3. Beta motor neurons * "A few somatic efferent neurons called beta motor neurons innervate both intrafusal and extrafusal muscle fibers" (Big Miller)

Answer 129

1. Spinocervicothalamic tract (mainly skin) 2. Spinothalamic tract (visceral and somatic) 3. Dorsal column postsynaptic tract (skin) (Big Miller)

Answer 130

Spinothalamic tract (visceral and somatic) (Big Miller)

Answer 131

1. Dorsal column postsynaptic tract (skin) 2. Spinocervicothalamic tract (skin) 3. Spinothalamic tract (visceral and somatic) (Big Miller)

Answer 132

1. Fasiculus cuneatus (mannus) 2. Fasiculus gracilis (pes)

Answer 133

1. Fasiculus cuneatus (thoracic limb) 2. Spinomedullary tract to nucleus Z (pelvic limb) (Big Miller)

Answer 134

* Receptors = annulospiral endings --\> type Ia (largest/fastest/myelinated fibers) sensory fiber --\> * DRG --\> dorsal funiculus --\> bifurcate into cranial and caudal branches * Collaterals of these branches go to the ventral horn and excite nearly all the alpha motor neurons that innervate the muscle being stretched * Collateral branches synapse motor neurons of synergist muscles * Collaterals synapse on interneurons --\> inhibit motor neurons of antagonist muscles (Big Miller)

Answer 135

Free nerve endings associated with small myelinated fibers and nonmyelinated axons --\> DRG --\> enter dorsolateral fasiculus and bifurcate into cranial and caudal branches Cranial and caudal branches extend over several segments --\> collateral branches that enter gray matter to synapse on interneurons and projection neurons Interneurons excite all flexors of the limb and inhibit reciprocal muscles (Big Miller)

Answer 136

* Ratio of white matter to gray mater is the greatest - cervical segments * spinal cord perimeter oval in transverse segments - cranial cervical region * Spinal cord perimeter appears circular - thoracic segments (between intumescence) * Dorsal intermediate sulcus ad septum evident - cranial half of the spinal cord * Dorsal median fissure - lumbar and sacral segments * Apex of the dorsal gray horn pointed - cervical * Apex of the dorsal horn blunted - thoracic region * Apex of the dorsal horn rectangular - lumbosacral region * Lateral gray horn evident - thoracic and cranial lumbar segment (Big Miller)

Answer 137

GSE: * Mesencephalon at the level of the rostral colliculi * Adjacent to the mesencephalic aqueduct * Within the ventral portion of the central gray substance that surrounds the aqueduct GVE: * Rostral to the GSE nucleus * Caudal to the pretectal nucleus * Similar position in relation to mesencephalic aqueduct (Big Miller)

Answer 138

GSE axons: * Pass ventrally through the reticular formation of the tegmentum, remain medial * Emerge on the lateral side of the interpeduncular fossa * Form the oculomotor nerve on the medial side of the crus cerebri * Course rostrally in the middle cranial fossa (lateral to the pituitary gland, adjacent to the cavernous sinus) * Leaves cranial cavity through the orbital fissure * Within the periorbita courses laterally with CN II shortly * Branches to supply: * Medial, dorsal, and ventral rectus muscle * Ventral oblique muscle * Levator palpebrae superioris muscle GVE axons: * GVE axons are located superficially in CN III * At point of branching to muscular branches - CILIARY GANGLION * Telodendrons of GVE preganglionic neurons synapse on the dendritic zones of the cell bodies of the ganglionic neurons * Ganglionic axons pass via short ciliary nerves along the surface of the optic nerve --\> eyeball --\> smooth muscle of the ciliary muscle and sphincter of the pupil (de Lahunta)

Answer 139

Nucleus: * Located in the caudal mesencephalon, level of the caudal colliculi * Adjacent to the mesencephalic aqueduct Axons: * Courses lateral, dorsal, and caudal --\> enter rostral medullary velum --\> cross to opposite side and emerge caudal to the caudal colliculus * Continue rostrally and ventrally on the side of the mesencephalon --\> floor of the middle cranial fossa * Continue rostrally, lateral to the pituitary gland, adjacent to cavernous sinus * Leave cranial cavity through orbital fissure * (horses - sometimes leaves through trochlear foramen) * Within periorbita: * Innervates contralateral dorsal oblique muscle (pulls dorsal part of the eye medially)

Answer 140

Nucleus: * Located in the motor nucleus of the abducent nerve in the rostral medulla at the level of the caudal cerebellar peduncle * Close to midline, adjacent to 4th ventricle * GSE axons of the genu of the facial nerve pass over this nucleus Axons: * Ventrally through the reticular formation of the medulla * Pass through trapezoid body * Emerge just lateral to the pyramid * Course on the floor of the middle cranial fossa, beside the pituitary, adjacent to the cavernous sinus * Leaves the cranial cavity through the orbital fissure * Within the periorbita, branches to innervate the lateral rectus and retractor bulbi muscles (Big Miller)

Answer 141

Oculomotor nerve strabismus - present in all head positions Vestibular nerve strabismus - only present with certain head positions (de Lahunta)

Answer 142

Nucleus: * Motor nucleus of the trigeminal nerve * Located in the pons @ level of the middle and rostral cerebellar peduncles * Medial to the pontine sensory nucleus * Dorsolateral within the pons Axons: * Leave pons ventrolaterally, go through middle cerebellar peduncle --\> join sensory neurons entering the pons * As they emerge from the pons, may be seen as a separate motor nerve root on the medial aspect of the incoming sensory fibers --\> leaves in the canal for the trigeminal nerve (petrosal temporal bone) * Within the canal for the trigeminal nerve, motor neurons pass through the large trigeminal ganglion without synapsing * Mandibular nerve leaves through the OVAL foramen --\> muscles of mastication (Uemura/de Lahunta)

Answer 143

CN VII GSE nucleus: * Facial nucleus in the rostral medulla, located ventrolateral * Medial is the pyramid, lateral is the spinal nucleus of the trigeminal nerve, rostral is the trapezoid body * @ the level of attachment of the caudal cerebellar peduncle to the cerebellum Axons: * Course dorsorostrally toward the 4th ventricle, pass rostrally over the motor nucleus of the abducent nerve forming the **genu of the facial nerve** * Emerge from the medulla through the **trapezoid body**, ventral to the incoming CN VIII * Leaves through **internal acoustic meatus** alongside CN 8 --\> enters the facial canal within the temporal bone --\> **stylomastoid foramen** * @ **facial canal** - separated from the tympanic cavity by a thin layer of connective tissue * Branches of the facial nerve: * Stapedius nerve (branches within the facial canal) --\> stapedius muscle * Caudal auricular nerve --\> retroauricular muscle * Digastric nerve --\> caudal digastricus * Auriculopalpebral --\> rostral auricular muscles, orbicularis oculi muscles * Dorsal buccal --\> maxillonasolabialis muscle * Ventral buccal nerves --\> ventral orbicularis oris muscle (de Lahunta, Uemura)

Answer 144

CN IX * Cell bodies located in the rostral portion of the nucleus ambiguus (motor nucleus of the glossopharyngeal nerve) * Nucleus ambiguus - ill defined column of neuronal cell bodies ventrolateral medulla Axons * Axons go dorsally, then ventrolaterally --\> emerge along lateral medulla w/ GVE preganglionic axons of CN IX * Just caudal to CN VIII * Enters jugular foramen, exits tympanooccipital fissure * Gives rise to (GSE branches) * Pharyngeal beach - forms pharyngeal plexus w/ pharyngeal branches of CN X and sympathetic fibers of cranial cervical ganglion --\> innervates pharyngeal muscles (GSE component of CN IX is whimpy in comparison to GVE and GSA) (de Lahunta)

Answer 145

CN X * Cell bodies in the middle portion of the nucleus ambiguus = motor portion of the vagus nerve Axons: * Similar intramedullary course with CN IX GSE axons - course dorsally then ventrolaterally --\> emerge on the lateral aspect of the medulla, just rostral to the internal branch of the accessory nerve * Joined by preganglionic GVE CN X axons = motor portion of vagus nerve * Leaves through jugular foramen --\> GSE of internal branch of accessory nerve join --\> leaves tympanooccipital fissure * Pharyngeal branch --\> pharyngeal plexus with CN IX --\> striated muscle of the palate, pharynx, and cervical esophagus * Cranial laryngeal branch --\> cricothyroid muscle * Recurrent laryngeal (contains GSE of internal accessory branch) --\> caudal laryngeal nerve --\> all other intrinsic muscles of the larynx * Recurrent laryngeal nerve innervates the cervical and cranial thoracic esophagus * Small branches from vagus nerve --\> directly to esophagus (de Lahunta)

Answer 146

CN XI * Internal branch: cell bodies located in the caudal nucleus ambiguus * External branch: cel bodies located in the motor nucleus of CN XI - lateral gray horn of C 1-8 Axons pass: * Internal branch: course dorsally then ventrolaterally within the medulla --\> emerge on the lateral aspect of the medulla as the cranial roots of CN XI --\> jugular foramen --\> join CN X GSE and GVE --\> tympanooccipital fissure * Innervate: * Intrinsic muscles of the larynx * Cervical and cranial thoracic esophagus (via recurrent laryngeal) * External branch: axons emerge from the lateral cervical spinal cord as the spinal roots of the accessory nerve --\> form external branch of the accessory nerve --\> courses cranially just dorsal to the denticulate ligament between the dorsal and ventral rootlets --\> foramen magnum --\> joins the internal branch of CN XI for a few mm --\> jugular foramen --\> internal branch joins vagus nerve * Emerges from TOF (accessory nerve that emerges from TOF contains only GSE neurons from the external branch * Innervates: * Trapezius * Sternocephalicus * Cleidocephalicus (de Lahunta)

Answer 147

CN XII * GSE neuronal cell bodies located in the motor nucleus of the hypoglossal nerve in the medulla * Adjacent to the median plane and to the floor of the 4th ventricle * Long nucleus Axons pass: * Directly ventral and lateral from the nucleus through the reticular formation --\> emerge lateral to the pyramid as a longitudinal series of small roots * Row of hypoglossal roots merges at the small hypoglossal canal --\> hypoglossal canal * Innervate: * Extrinsic tongue muscles * Intrinsic tongue muscles * geniohyoideus * The nerve is much smaller inside the cranial cavity than outside the skull - this is the result of increase in myelination and connective tissue that occurs after the nerve merges from the hypoglossal canal (de Lahunta)

Answer 148

Voltage-gated Na channel: Activation gait is closed, inactivation gate open Voltage-gated K+ channel: gate closed Conductance for K+ is 50 - 100x greater than conductance for Na+ This is due to leakage of K+ through leak channels (Guyton)

Answer 149

Conformational change in the voltage-gated Na channel activation --\> open conformation Voltage gated K+ channel opens but much slower rate than VGNa channel Na conductance becomes 10x greater than K conductance (Guyton)

Answer 150

Voltage-gated Na channel - inactivation gate closed. Voltage-gated K channel open - K+ diffuses out of the cell Conductance of K is becoming greater than Na again (Guyton) | (The inactivation gate will not reopen until the membrane potential returns to or near the original resting membrane potential)

Answer 151

Deficit of Ca --\> nerve is hyperexcitable Na channels become activated by a small increase of the membrane potential Ca appears to bind the exterior surface of the Na channel --\> alters the voltage-level required to open the gate (Guyton)

Answer 152

5-50x (Guyton)

Answer 153

True cell membrane + an outer coat of polysaccharide material containing collagen fibrils Myofibrils are composed of actin and myosin (Guyton)

Answer 154

Myosin filament - 200+ myosin molecule Each myosin molecule is an ATPase Actin * Polymerized g-actin makes up F actin strands which are interlaced with tropomyosin * Troponin - 3 subunits that are attached to tropomyosin * Troponin + tropomyosin - inhibit interaction of actin and myosin (Guyton)

Answer 155

I band = light band - actin only Dark band = A band = actin and myosin Z disk = structure that attaches actin filaments Sarcomere is the unit between z disks (Guyton)

Answer 156

Titin (Guyton)

Answer 157

* Action potential depolarizes muscle membrane and causes the sarcoplasmic reticulum to release lg quantities of calcium ions * Ca inhibits troponin/tropomyosin complex --\> allows interaction of myosin + actin * Uncovered actin filament --\> binds actin --\> conformational change in myosin head --\> "power stroke" (involves release of ADP, binding and cleavage of new ATP molecule) * After a fraction of a second, the calcium ions are pumped back into the sarcoplasmic reticulum by Ca2+ membrane pump and remain stored in the reticulum until a new muscle action potential comes along * This removal of calcium ions from the myofibrils causes the muscle contraction to cease (Guyton)

Answer 158

* Phosphocreatine - carries high energy phosphate bond similar to ATP * Slightly higher amount of free energy than each ATP bond * The total amount of phosphocreatine in the muscle fiber is small * Glycolysis of glycogen * Occurs in the absence of oxygen, can be sustained for up to a minute * Accumulation of the end products of glycolysis limits its ability to continue * Oxidative metabolism * Combining oxygen w/ end products of glycolysis (and other cellular food stuffs) to create ATP * More than 85% of all energy used by muscles for sustained long term contraction is derived from oxidative metabolism (Guyton)

Answer 159

Slow: * Type I * Small muscle fibers * Small nerve fibers * Rich blood supply and capillaries * High # mitochondria for oxidative phosphorylation, few glycolytic enzymes * High qty of myoglobin (red color) Fast: * Type II * Extensive sarcoplasmic reticulum for strongest possible contraction * Large muscle fibers * Large nerve fibers * Limited blood supply * Few mitochondria, extensive glycolytic enzymes * Small amount of myoglobin - more white in color (Guyton)

Answer 160

True - but there is no myelin Sarcolemma has an invaginated membrane = synaptic gutter/trough with smaller folds of muscle membrane = subneural clefts Increases surface area for neurotransmitter

Answer 161

Acetylcholine is synthesized in the cytoplasm of the nerve --\> stored in vesicles Action potential spreads to the nerve terminal --\> voltage-gated Ca channels open --\> Ca ions diffuse from synaptic space to the interior of the nerve terminal Ca ions activate Ca-calmodulin dependent protein kinase --\> phosphorylates synapsin proteins --\> which allows ACh vesicles to be freed from the cytoskeleton and move to the active zone of the presynaptic membrane (adjacent to the dense bars) --\> vesicles dock at release sites and fuse with he neural membrane --\> empty ACh into synaptic space via exocytosis (Guyton)

Answer 162

2 The nicotinic ACh receptor has 5 subunits 2 ACh molecules attach to the alpha subunits --\> conformational change --\> opens the channel The channel is permeable to Na, K+, and Ca but more Na flows through than any other ion Binding of ACh to ACh-gated channel --\> excitatory potential of the myofiber

Answer 163

Acetate and choline Choline is quickly reabsorbed - reused to form new acetylcholine Within a few seconds after each AP is over, coated pits appear in the terminal nerve membrane. Proteins contract and cause the pits to break away to the interior of the membrane --\> new vesicles ACh is transported to the interior of the new vesicles --\> ready for a new cycle of ACh release (Guyton)

Answer 164

Competitive, reversible inhibition of acetylcholinesterase * Similar chemical structure to acetylcholine, polar quaternary ammonium structure * Binds acetylcholinesterase and causes transfer of a carbamyl molecule to the catalytic site of the enzyme - blocks hydrolytic activity * Half-life: neostigmine - 8-21 min; pyridostigmine - 23 - 82 min * Adverse reaction w/ levamisole (Madison pharmacology)

Answer 165

Duration of action potential about 1-5ms (5x longer than large myelinated nerve fiber) (Guyton)

Answer 166

Voltage changes --\> activation of dihydropyridine receptors --\> opening of Ca-release channels on sarcoplasmic reticulum membrane (AKA ryanodine receptor) Continually active Ca pump located in the walls of the sarcoplasmic reticulum pumps Ca ions out of the sarcoplasm and into the sarcoplasmic tubules Calsequestrin - protein found within sarcoplasmic reticulum that can bind 40x more concentration Ca

Answer 167

* Receptor is activated by neurotransmitter --\> receptor undergoes conformational change exposing a binding site for G protein complex * G protein complex binds --\> permits alpha subunit to release GDP and bind GTP while separating from the beta/gamma portions of the complex * Alpha-GTP complex is free within the cytosol to perform various functions * Opening specific ion channels through postsynaptic cell membrane * Activation of cAMP or cGMP --\> initiate metabolic shift --\> long term excitability can be altered * Activation of intracellular enzymes * Activation of gene transcription (Guyton)

Answer 168

Small molecule transmitters are synthesized in the cytosol of the presynaptic terminal Packaged into transmitter vesicles via active transport The vesicles that store and release small molecule transmitters are continually recycled (Guyton)

Answer 169

Excitatory: * Acetylcholine * Norepi - secreted @ locus coeruleus, sympathetic * Glutamate Inhibitory * Dopamine - secreted @ substantia nigra * Glycline - secreted @ spinal cord * GABA Other: * Serotonon - secreted @ median raphe nucleus * NO (not stored in vesicles, synthesized as needed and diffuses between membranes (Guyton)

Answer 170

Synthesized in soma by ribosomes as lg protein molecules, enter the endoplasmic reticulum and are packaged in the Golgi apparatus Within the Golgi apparatus, the larger protein molecules are split into smaller fragments (either neuropeptide or other neuropeptide precursor) Golgi packages neuropeptide into transmitter vesicles --\> releases vesicles --\> transported down axon (slow transport) --\> released at neuron terminal in response to action potential Vesicle is autolyzed and not reused Smaller quantities are released (as compared to small molecule neurotransmitters), they are more potent (Guyton)

Answer 171

Ventral horn motor neuron - -65mV Peripheral nerve fiber, muscle fiber -90mV (Guyton)

Answer 172

Resting membrane potential due to Na only = +61 mV If Na were allowed to flow freely, the membrane potential would be +61 on the inside compared to outside once it equilibrated Resting membrane potential due to K+ only = -86mV If K+ were allowed to flow freely, it would leave -86mV inside the cell once equilibrated Resting membrane potential due to Cl only = -70mV Chloride is high in the extracellular fluid and low intracellular Membrane is permeable to Cl ions but since the Na/K pump leaves the interior of the cell negative, Cl does not diffuse inside (Guyton)

Answer 173

There are no/few voltage-gated Na channels at the dendrites, they are found at the axon hillock Excitatory postsynaptic potential of +10-20mV in the axon hillock will initiate an AP, requires +30-40mV in the dendrites/soma (Guyton)

Answer 174

Open chloride channels --\> hyperpolarizes the nerve Open K+ channels --\> hyperpolarizes the nerve Increase in negativity beyond the normal resting potential is called inhibitory postsynaptic potential (Guyton)

Answer 175

Spatial summation: Multiple presynaptic terminals stimulate the same neuron at different sites but at the same time --\> summation of EPSP --\> action potential Temporal summation: one presynaptic terminal stimulates a neuron at the same site repeatedly --\> summation of EPSP --\> action potential (Guyton)

Answer 176

Before the excitatory potentials reach the soma, a share of the potential is lost by leakage through the membrane This decrease in membrane potential as it spreads along dendrites towards the soma is called decremental conduction The farther the excitatory synapse from the soma, the greater will be the decrement and the lesser will be excitatory signal reaching the soma Therefore synapses that lie near the soma are more influential (Guyton)

Answer 177

Fatigue: Excitatory synapses fire at a rapid rate --\> number of discharges by the postsynaptic neuron is at first very great, firing rate becomes progressively less in succeeding ms or seconds Mechanism: * Exhaustion of supply or transmitter substance * Progressive inactivation of postsynaptic membrane receptors * Slow development of abnormal concentrations of ions inside postsynaptic cell (Guyton)

Answer 178

Alkalosis increases neuronal excitability Hyperventilation --\> blows off CO2 --\> elevated pH --\> may precipitate epileptic attack Acidosis depressed neuronal activity (Guyton)

Answer 179

Hypothalamus * Rostral nuclei - parasympathetic * Caudal nuclei - sympathetic * Input from: cerebrum, thalamic nuclei, ascending GVA pathways * Outut to: Reticular formation (de Lahunta)

Answer 180

Sympathetic: Lateral gray column of T1-L4/5 Sympathetic ganglia are located close to the CNS --\> ganglionic (postganglionic) axons are fairly long Parasympathetic: CN nuclei 3, 7, 9, 10; Lateral gray column of S1-3 Parasympathetic ganglia are located close to the target organ --\> ganglionic axin are short (de Lahunta)

Answer 181

Retina --\> optic nerve --\> optic chiasm --\> optic tracts --\> pass over LGN and synapse on pretectal nuclei (rostral midbrain) - -\> axons cross at caudal commissure --\> contralateral CN3 nucleus - -\> smaller # axons do not cross --\> ipsilateral CN 3 nucleus (de Lahunta)

Answer 182

Pupillary sphincter is circularly arranged Pupillary dilator muscle is radially arranged

Answer 183

* Cell bodies are in the lateral gray horn of T1-3/4 * Leave with the ventral root --\> ramus communicans --\> course cranially in the sympathetic trunk --\> * pass through cervicothoracic and middle cervical ganglia --\> join cervical vagosympathetic trunk (within carotid sheath) --\> cranial cervical ganglion * This ganglion is located medial to the origin of the digastricus, ventromedial to the tympanic bulla * "Pathway from cranial cervical ganglion to eye is not well defined" * As a rule, ganglionic sympathetic axons follow blood vessels * In the cat, these axons pass through the tympanic cavity on the ventral surface of the petrous temporal bone * Tympanic cavity --\> run ventral to the trigeminal ganglion --\> enter the cranial cavity via TOF --\> join the ophthalmic nerve branch of the trigeminal nerve --\> orbit/periorbita * Innervate: * Pupillary dilator * Ciliary muscle --\> increase lens curvature * Orbitalis muscle = smooth muscle of the periorbita/eyelids (third eyelid) (de Lahunta)

Answer 184

Sympathetic trunk ganglia are paired and line on the ventrolateral surface of the vertebral column EXCEPT in the cervical and cranial thoracic region * Preganglionic sympathetic fiber cell body in lateral horn --\> leaves w. ventral root --\> branches off spinal nerve --\> communicating branch (ramus communicans) --\> joins sympathetic trunk and synapses @ sympathetic trunk ganglia --\> * The sympathetic trunk ganglia caudal to the cranial thoracic region are segmentally related to the adjacent vertebrae * These ganglia are numbered according to the spinal nerve to which the preganglionic sympathetic fibers join * The sympathetic trunks extend caudally into the sacral and coccygeal vertebrae * Paired trunks are sometimes partially fused here (Uemura)

Answer 185

Cranial cervical ganglion: * Lateral gray horn of T1-3 --\> communicating branch --\> pass through cervicothoracic/middle cervical ganglion --\> vagosympathetic trunk --\> cr. cervical ganglion (Uemura)

Answer 186

T1-3 lateral gray horn --\> ventral roots --\> communicating branch --\> sympathetic trunk --\> pass through cervicothoracic ganglion w/o synapse --\> ansa subclavia --\> middle cervical ganglion --\> cardiosympathetic fibers to the heart/airways * Middle cervical ganglion - located just cranial to the ansa subclavian, @ thoracic inlet (Uemura)

Answer 187

T1-3/4 lateral gray horn --\> ventral roots --\> communicating branch --\> sympathetic trunk --\> cervicothoracic ganglion * Postganglionic axons --\> heart and lungs * Vertebral nerve --\> postganglionic axons distributed with C3-8 Cervicothoracic ganglion: located just medial to the first rib

Answer 188

Lateral tectotegmentospinal system * Hypothalamus --\> brainstem --\> lateral funiculus --\> lateral gray horn from T1-L4/5 --\> synapse on dendritic zones of the pregenglionic neurons of the sympathetic GVE LMN * The activity of this system is necessary for GVE LMN to function (de Lahunta)

Answer 189

S1-3 spinal cord segments lateral gray horn --\> ventral roots --\> spinal nerve --\> ventral branches --\> parasympathetic fibers branch off * Parasympathetic fibers from S1-3 form a single pelvic nerve that runs ventrally on the lateral surface of the rectum * Ventral to the rectum, they meet hypogastric nerves and form pelvic plexus * Parasympathetic preganglionic axons can synapse @ the pelvic ganglion --\> postganglionic axons travel to the detrusor muscle * Or parasympathetic preganglionic axons travel through the pelvic plexus w/o synapse --\> detrusor muscle and synapse w/ postganglionic axon there Postganglionic parasympathetic axons in the detrusor synapse on muscarinic cholinergic receptors (M2 and M3) of the smooth muscle of the bladder (aka detrusor) (de Lahunta)

Answer 190

Preganglionic cell body is in the lateral gray horn of L1-4 or L5 --\> axons leave w/ ventral root --\> spinal nerve --\> axons leave spinal nerve (communicating branch) --\> sympathetic trunk --\> leave w. lumbar splanchnic nerves --\> caudal mesenteric ganglion * Postganglionic axons form hypogastric nerves --\> intermix @ pelvic plexus with pelvic nerve * Postganglionic axons can synapse/terminate @ pelvic plexus on the dendrite/cell body of postganglionic parasympathetic neurons * Alpha 2 receptors on parasympathetic nerves --\> when stimulated, the parasympathetic neuron is inhibited from generating an impulse --\> prevents detrusor contraction * Postganglionic axons can continue to the neck of the bladder --\> smooth muscle of internal urethral sphincter --\> alpha 1 receptors * Postganglionic axons can continue to the detrusor muscle beta 3 receptors (de Lahunta)

Answer 191

A-delta mechanoreceptors --\> GVA fibers that run with the pelvic nerve and hypogastric nerve --\> cell body in DRG --\> synapses @ dorsal horn * The next neuron decussates --\> travels in spinothalamic/spinoreticular tract to the pontine micturition center and to thalamus/cerebrum (de Lahunta)

Answer 192

Distention of the bladder --\> low-level visceral afferent firing --\> stimulates sympathetic outflow: Sympathetic * Sympathetic: * Releases norepi @ detrusor --\> activated INHIBITORY B-adrenergic receptors in the detrusor muscle --\> relaxes the bladder * @ IUS--\> activates alpha-1 adrenergic receptors --\> contraction of smooth muscle * @ Pelvic ganglion --\> activates alpha 2 receptors on parasympathetic postganglionic axons --\> inhibits detrusor contraction * Parasympathetic: inhibited * GSE: Pudendal nerve releases ACh on nicotinic cholinergic receptor --\> voluntary contraction of external sphincter "A region in the rostral pons (the pontine storage centre) might increase striated urethral sphincter activity"

Answer 193

Bladder volume increases --\> exceeds threshold of GVA mechanoreceptors that respond to stretch and distention --\> impulses via pelvic nerve --\> sacral dorsal gray column * Ascending signal travels via spinothalamic tract --\> pontine micturition center * Also travels to thalamic nuclei --\> cerebral cortex * Also travels to cerebellum (who knows why) * Pontine micturition center --\> reticulospinal tract * Lumbar segments --\> inhibits sympathetic input to detrusor and IES * Sacral segments --\> * Facilitates parasympathetic input --\> releases ACh on muscarinic receptors --\> destrusor contraction * Inhibits pudendal GSE --\> relax EUS (deLahunta)

Answer 194

* Sacral segments --\> parasympathetic preganglionic neurons --\> pelvic nerves --\> wall of GI tract --\> postganglionic neuron * Facilatoryy * L1-L4 or 5 --\> caudal mesenteric ganglion/plexus --\> hypogastric nerves --\> pelvic plexus --\> GVE LMN to descending colon/rectum and internal anal sphincter * Sacral spinal cord segments GSE LMN --\> sacral plexus --\> caudal rectal branch of the pudendal nerve --\> striated external anal sphincter * GVA --\> cranially projecting sensory spinal cord tracts to a poorly localized brainstem center --\> defecation analogous to micturition Thalamic nuclei exist for relay to the sensory cerebral cortex (de Lahunta)

Answer 195

Parasympathetic nucleus of the facial nerve * Located dorsal in the medulla, adjacent to the 4th ventricle Axons: * Join GSE motor neurons --\> internal acoustic meatus --\> facial canal * Within the facial canal the axons of the major petrosal nerve branch off --\> joined by deep petrosal nerve (sympathetic ganglionic axons) --\> pterygopalatine ganglion (on the pterygoid muscles) * Postganglionic parasympathetic axons join trigeminal nerve branches * Lacrimal gland * Gland of the 3rd eyelid * Palatine glands * Lateral and mucosal nasal glands * Within the facial canal (after major petrosal nerve) the axons of the chorda tympani branch off --\> courses through tympanic cavity --\> joins lingual nerve (branch of the mandibular nerve, contains sympathetic fibers) --\> sublingual and mandibular salivary ganglion * Sublingual salivary gland * Mandibular salivary gland (de Lahunta)

Answer 196

Parasympathetic nucleus of the glossopharyngeal nerve * Just caudal to the parasympathetic nucleus of the facial nerve (ventolateral to the 4th ventricle) Axons: * Join GSE axons of the nucleus ambiguus --\> glossopharygeal nerve --\> jugular foramen --\> preganglionic axons leave as tympanic nerve (before TOF) * Preganglionic axons go to tympanic cavity and form tympanic plexus --\> minor petrosal nerve --\> otic ganglion * Otic ganglion is located just ventral to the oval foramen/mandibular nerve * Postganglionic axons join branches of mandibular nerve --\> * Parotid and zygomatic salivary glands (de Lahunta)

Answer 197

Parasympathetic nucleus of the vagus * located in column with nuclei of 7, 9, 10 ventrolateral to the 4th ventricle in the medulla Axons * GVE axons join GSE axons of the nucleus ambiguus --\> CN 10 --\> jugular foramen --\> TOF * GVE Parasympathetic preganglionic axons course caudally with the vagosympathetic trunk --\> * Mediastinum --\> branches with the vagus nerve to the heart, smooth muscle and glands of the lungs/esophagus * Postganglionic neurons are located in the wall of these organs * Abdomen with the dorsal and ventral vagal trunks --\> blood vessels to abdominal organs --\> synapse on postganglionic axons within the wall of the viscera (de Lahunta)

Answer 198

Vestibule Cochlear window (de Lahunta)

Answer 199

Spiral lamina (de Lahunta)

Answer 200

Cochlear duct * Contains endolymph * Apex of the triangle attaches medially to the spiral lamina of the modiolus * Base = stria vascularis, then cochlea * Ventral = scala tympanum, separated by basilar membrane * Dorsal = scala vestibuli, separated by vestibular membrane * Continuous with the saccule via the ductus reuinens (de Lahunta)

Answer 201

* Contains perilymph * Dorsal to the cochlear duct, separated by the vestibular membrane * Communicates with the stala tympani @ helicotrema * Communicates with the vestibule of the bony labyrinth (de Lahunta)

Answer 202

Scala tympani * Contains perilymph * Located ventral to the cochlear window, separated by the basilar membrane * Continuous with the scala vestibuli @ the helicotrema * Continuous with the subarachnoid space by the perilymphatic duct * Ends @ cochlear window (de Lahunta)

Answer 203

Spiral organ of Corti: * Located on the basilar membrane * Hair cells have stereocilia that are embedded in the tectorial membrane * The dendrites of CN 8 are in synaptic relationship with the base of the hair cells (de Lahunta)

Answer 204

Sound waves are transmitted from the air medium of the external ear canal --\> tympanum --\> ossicles (malleus, incus, stapes) --\> vestibular window --\> perilymph --\> scala vestibuli --\> helicotrema --\> scala tympani --\> vibration of basilar membrane --\> movement of the tectorial membrane --\> movement of the stereocilia --\> hair cells send signal to dendrites of CN 8 (de Lahunta)

Answer 205

the basilar membrane is longest at the base of the cochlear coil, progressively shortens through the coils to the apex High frequencies --\> maximally affect the basal portion of the basilar membrane Low frequencies --\> maximal vibration of the basilar membrane at the apex

Answer 206

Stapes Malleus (specifically the manubrium of the malleus)

Answer 207

The tensor tympani muscle connects to the malleus. It is innervated by the mandibular nerve Chorda tympani crosses the medial surface of the malleus, then joins the lingual nerve The stapedius muscle connects to the stapes. It is innervated by the facial nerve (Uemura)

Answer 208

Dendrites of CN 8 cochlear portion are in synaptic contact with hair cells of the spiral organ --\> cell bodies within the modiolus --\> CN 8 divisions join --\> internal acoustic meatus --\> cerebellomedullary angle --\> dorsal and ventral cochlear nuclei on the lateral side of the medulla

Answer 209

1. Ventrally through the trapezoid body * Cochlear nuclei --\> Ipsilateral nucleus of the trapezoid body, or decussates to contralateral nucleus of the trapezoid body 2. Dorsally over the caudal cerebellar peduncle by way of the acoustic stria * Cochlear nuclei --\> axon courses dorsally, decussates, ascends in the lateral lemniscus (de Lahunta)

Answer 210

Afferent neurons of CN 8 --\> cochlear nuclei --\> motor nucleus of the trigeminal nerve--\> mandibular br of trigeminal --\> tensor tympani muscle Cochlear nuclei --\> facial nerve GSE --\> stapedius muscle (de Lahunta)

Answer 211

Contains fibers from the cochlear nuclei, dorsal nucleus of the trapezoid body, ventral nucleus of the trapezoid body Fibers from ipsilateral and contralateral nuclei Terminates at the caudal colliculus The nucleus of the lateral lemniscus is located along the ventromedial aspect of the lateral lemniscus (de Lahunta)

Answer 212

1. Brainstem nuclei (tectonuclear pathway) 2. Cervical spinal cord (tectospinal in the ventral funiculus) 3. Thalamus (brachium of the caudal colliculus --\> medial geniculate nucleus) (de Lahunta)

Answer 213

Medial geniculate nucleus --\> internal capsule --\> neocortex of the temporal lobe * Primarily Sylvian and ectosylvian gyri * This rostrally projecting auditory pathway is characterized by diffuseness and a bilateral distribution * Despite this, at the cortical level, the contralateral cochlear duct is more strongly represented * Crossing occurs at the level of the trapezoid body, between the nuclei of the lateral lemniscus, at the commissure of the caudal colliculus (de Lahunta)

Answer 214

Stria vascularis Inner hair cells - primarily sensory Outer hair cells - primarily function to decrease or increase auditory sensitivity by contraction to shorten (via myosin within the cells) or increase sensitivity by relaxing Shortening --\> pulls the tectorial membrane --\> partially bends stereocilia of the inner hair cells --\> greater sensitivity (Brain Camp)

Answer 215

Cats are able to hear higher frequencies Dog: 67Hz - 45 KILOHz Cat: 45Hz - 64 KILO Hz (Brain Camp)

Answer 216

In the epidermis They are ensheathed in Schwann cells, just not myelinated (Uemura)

Answer 217

Meissner's Corpuscles * Encapsulated nerve ending of a large type Abeta myelinated sensory nerve fiber * Present in the dermis of the pads * Adapt quickly (Guyton)

Answer 218

**Merkel's discs** are present in the basal layer of the epithelium and are sensitive to touch and pressure Several cells innervated by the same myelinated nerve fiber (A beta) Considered a free nerve ending type of receptor Slowly adapting and remain active as long as the stimulus is present (Guyton)

Answer 219

**Hair end organ** are receptors involved with a hair follicle, detect movement of objects on the surface of the body * Considered a free nerve ending, present in the dermis * Adapt quickly (Guyton)

Answer 220

**Ruffini's endings** are multibranched, encapulated nerve endings that are important for signaling continuous states of deformation of the tissues * Adapt very slowly * Also found in joint capsules * Present in the dermis * Consist of myelinated axon terminals interspersed with collagen fibers and surrounded by several layers of perineural epithelioid cells (Guyton)

Answer 221

**Pacinian corpuscles** are stimulated by rapid local compression of the tissue and are the largest sensory receptors * Located immediately under the skin and deep in the facial tissues of the body * Also found as proprioceptors in joints * Adapt quickly * Made of an axon terminal surrounded by numerous concentric layers of perineural epitheloid cells (Guyton)

Answer 222

Phasic receptors - rapidly adapting receptors. They fire as they first receive a stimulus, stop firing if the stimulus magnitude stays unchanged Ex/ Paciniain and Meissner's corpuscles Tonic receptors - slowly adapting receptors. They continue to fire action potentials during the duration of stimulation Ex/ Merkel's corpuscles, Ruffini endings, baroreceptors (Uemura)

Answer 223

Sensory neurons innervating a given receptor field converge on smaller numbers of postsynaptic neurons Receptive field covered by a central neuron reflects a combined area monitored by various numbers of sensory neurons Large receptive fields allow the sensory neuron to detect stimulus applied to a wider area, but results in a less precise perception than small receptive fields (Uemura)

Answer 224

the second-order neuron (more specifically the number of primary sensory neurons converging onto a single second-order neuron) If a second order neuron receives signals from only 1 or 2 primary neurons, the receptive field of the second order neuron is small

Answer 225

1. Reflex activity (monosynaptic or polysynaptic w/ interneurons and fasiculus proprius) 2. Cerebellum 3. Cerebrum (de Lahunta)

Answer 226

Dorsal spinocerebellar tract * Muscle spindle --\> DRG T1-S --\> nucleus thoracicus in the dorsal gray horn --\> ipsilateral lateral funiculus as the dorsal spinocerebellar tract * Caudal cerebellar peduncle --\> cerebellum Ventral spinocerebellar tract * Golgi tendon --\> DRG T1-S --\> synapse @ base or dorsal gray horn --\> contralateral lateral funiculus as the ventral spinocerebellar tract * Located VENTRAL to the dorsospinocerebellar tract * Rostral cerebellar peduncle --\> cerebellum (de Lahunta)

Answer 227

1. Cuneocerebellar tract (C1-T8) 2. Cranial (rostral) spinocerebellar tract (C1-T1) 3. Cervicospinocerebellar pathway 4. Cervicospinovestibular pathway (de Lahunta)

Answer 228

Cuneocerebellar tract: * Muscle spindle in DRG of C1-T8 --\> dorsolateral funiculus (fasiculus cuneatus) as the cuneocerebellar tract (without synapse) * Synapse @ lateral cuneate nucleus of the medulla * Caudal cerebellar peduncle --\> cerebellum Cranial (rostral) spinocerebellar tract * Golgi tendon in DRG of C1-T1 --\> centrobasilar nucleus of dorsal gray horn --\> ipsilateral lateral funiculus as the cranial spinocerebellar tract * Enter the caudal and rostral cerebellar peduncles (de Lahunta)

Answer 229

Cervicospinocerebellar * Proprioceptors of the neck that join DRG C1-5 --\> central cervical nucleus (intermediate gray column) --\> contralateral lateral funiculus as cervicospinocerebellar pathway * Caudal cerebellar peduncle Cervicospinovestibular * Proprioceptors of cervical muscles --\> dorsal gray horn --\> ipsilateral ventral funiculus as cervicospinovestibular pathway * --\> caudal vestibular nucleus (de Lahunta)

Answer 230

Caudal to T6: Proprioceptors --\> DRG --\> dorsal funiculus w/o synapse Join **fasiculus gracilis** --\> **nucleus gracilis** in the medulla Cranial to T6: Proprioceptors --\> DRG --\> dorsal funiculus w/o synapse Join **fasiculus cuneatus** (lateral to gracilis) --\> **medial cuneate nucleus** in the medulla The axons from the nucleus gracilis/medial cuneate nucleus --\> decussate in medulla as **deep arcuate fibers** --\> medial lemniscus Entire spinal cord: Proprioceptors --\> DRG --\> **nucleus proprius** (dorsal horn) --\> ipsilateral lateral funiculus (as **spinocervical tract**) --\> **lateral cervical nucleus** (dorsal horn C1-2) --\> decussate in caudal medulla --\> medial lemniscus Collaterals of **dorsal spinocerebellar tract** --\> **nucleus Z** --\> internal arcuate fibers --\> medial lemniscus **Medial lemniscus** --\> ventral caudal lateral nucleus of the thalamus --\> thalamocortical fibers --\> internal capsule, centrum semiovale --\> somesthetic cortex of the cerebral hemisphere (de Lahunta)

Answer 231

GP receptor organs in the: * Muscles of mastication * Facial and extraocular muscles * Temporomandibular joints --\> GP axons join all 3 branches of the trigeminal nerve --\> enter pons w/o synapse --\> mesencephalic nucleus of the trigeminal nerve Axons from mesencephalic nucleus of the trigeminal nerve --\> * GSE alpha-LMN of cranial nerve nuclei * Pontine sensory nucleus of the trigeminal nerve --\> Cranial nerve GSE neuron (de Lahunta)

Answer 232

GP (muscles of mastication, extraocular muscles, TMJ joint, temporal muscles) --\> trigeminal nerves --\> mesencephalic nucleus of the trigeminal nerve --\> pontine sensory nucleus of the trigeminal nerve --\> decussate --\> join contralateral trigeminal lemniscus (aka quintothalamic tract) --\> medial lemniscus --\> ventral caudal medial nucleus of the thalamus --\> internal capsule --\> centrum semiovale --\> somesthetic cortex (de Lahunta)

Answer 233

Pain (nociception), temperature, touch system Proprioception is carried in General Proprioceptive system (de Lahunta)

Answer 234

Free nerve endings, Merkel's corpuscle, Meissner's corpuscle, Pacinian corpuscle --\> general somatic afferent (pain, touch, temp system) Muscle spindles, Golgi tendon organ (also Pacini and Ruffini) (Uemura)

Answer 235

Temp/nociception/touch --\> DRG --\> dorsolateral sulcus --\> dorsolateral fasiculus Within the spinal cord, the GSA axon forms relatively short branches that course cranially and caudally on the surface of the dorsal gray column for 2-3 segments (called dorsolateral fasiculus) Collaterals of dorsolateral fasiculus --\> dorsal gray column and synapse on substantia gelatinosa \*\* S. gelatinosa is located on the apex of the dorsal horn S. gelatinosa neurons --\> middle of the dorsal gray horn --\> interneurons --\> * GSE alpha motor neuron in the ventral gray horn * Axon of interneuron enters fasiculus proprius --\> cranially/caudally --\> GSE alpha LMN in adjacent spinal cord segments (de Lahunta)

Answer 236

Dermatome - area of cutaneous sensation for an individual dorsal root (spinal nerve) Cutaneous area - area of cutaneous sensation for one named nerve. Considerable overlap Autonomous zone - area of cutaneous sensation belonging to only one specific named nerve

Answer 237

Serotonin Bradykinin Prostaglandins (de Lahunta)

Answer 238

Laminae I-VI are in the dorsal gray horn Neurons that participate in the nociceptive pathway are located in all 6 of these laminae Lamina II = substantia gelatinosa (de Lahunta)

Answer 239

1. Spinothalamic 2. Dorsal column postsynaptic pathway 3. Spinocervicothalamic pathway 4. Spinomesencephalic pathway (de Lahunta)

Answer 240

Nociceptors --\> DRG --\> cell body in dorsal gray horn (Lamina I, II, V) --\> crosses to contralateral lateral funiculus (as spinothalamic tract) Spinothalamic tract ascends as a multisynaptic pathway (axons leave the tract, enter spinal cord gray matter, synapse on a neuronal cell body --\> reenters ipsilateral or contralateral spinothalamic tract @ brainstem --\> collaterals synapse in various reticular formation nuclei - activate ARAS Spinothalamic tract synapses on ventral caudal lateral nucleus of the thalamus --\> thalamocortical projection fibers --\> internal capsule --\> centrum semi ovale --\> somesthetic cortex (frontoparietal lobe) \*\* contralateral pathway predominates (de Lahunta)

Answer 241

Dorsal column postsynaptic pathway * Nociceptor --\> DRG --\> dorsal gray column (lamina III and IV) --\> fasiculus gracilus/fasiculus cuneatus --\> nucleus gracilis/**Z,** medial cuneate nucleus --\> decussate in medulla --\> medial lemniscus --\> thalamus Spinocervicothalamic pathway * Nociceptor --\> DRG --\> dorsal gray column (lamina III and IV) --\> ipsilateral lateral funiculus as spinocervicothalamic pathway --\> lateral cervical nucleus of C1-2 --\> decussate in medulla --\> medial lemniscus --\> thalamus Spinomesencephalic pathway * Nociceptor --\> DRG --\> doral gray column (lamina I and V) --\> decussate --\> contralateral ventrolateral funiculus as spinomesencephalic pathway --\> midbrain nuclei and thalamic nuclei * (rostral colliculus, red nucleus, cuneiform nucleus, interstitial nucleus, reticular formation, periaqueductal gray) (de Lahunta)

Answer 242

Most of the axons in the spinothalamic system cross at their origin A lesion that causes hemisection of the spinal cord --\> spastic paralysis of the ipsilateral pelvic limb, hypalgesia of the contralateral pelvic limb (exception is the spinocervicothalamic tract) (de Lahunta)

Answer 243

Dorsal gray horn: * Interneurons in the substantia gelatinosa are inhibitory to projection pathway neurons in other dorsal gray horn laminae ``` Periaqueductal gray (mesencephalon) + pontine locus coeruleus + medullary raphy nuclei --\> project caudally --\> dorsal gray column --\> inhibit nociceptive projection neurons \*\* some of this inhibition involves the release of serotonin ``` Nocieptive GSA neuronal cell bodies in the spinal ganglia produce substance P --\> released in dorsal gray horn \*\* Opiates and enkephalin inhibit the local action of substance P in the dorsal gray column (de Lahunta)

Answer 244

Nociceptor --\> branches of trigeminal nerve --\> trigeminal ganglion --\> pons --\> axons form spinal tract of the trigeminal nerve --\> * synapse on the pontine sensory nucleus of the trigeminal nerve * synapse nucleus of the spinal tract of the trigeminal nerve Axons from both of these nuclei --\> trigeminal lemniscus/qunitothalamic tract --\> medial lemniscus --\> ventral caudal medial nucleus of the thalamus --\> thalamocortical fibers --\> internal capsule --\> centrum semi ovale --\> somesthetic cerebral cortex (de Lahunta)

Answer 245

Nociceptors --\> branches of CN V --\> trigeminal ganglion --\> spinal tract of the trigeminal nerve --\> pontine sensory nucleus/nucleus of spinal tract of V --\> * Ipsilateral and contralateral facial nucleus GSE LMN (palpebral reflex) (de Lahunta)

Answer 246

Spinal tract of the trigeminal nerve continues into the first few spinal cord segments --\> dorsolateral fasiculus Nucleus of spinal tract of V --\> continuous with substantia gelatinosa (de Lahunta)

Answer 247

Pontine sensory nucleus - touch Nucleus of spinal tract of V - nociception and temperature Mesencephalic nucleus of V - proprioception The distribution of GSA to the face has a somatotopic organization to the axons and the nucleus of the spinal tract of the trigeminal nerve * GSA axons from ophthalmic division of V - located ventrally in the spinal tract (mandibular located dorsally, same goes for nucleus of spinal tract of V) * Cell bodies for nose and rostral muzzle within nuclear tracts are located rostrally * Cell bodies for the more caudal aspects of the head are located in the first few spinal cord segments (de Lahunta)

Answer 248

Touch, pressure, and joint proprioception (according to King's) de Lahunta says nociception as well

Answer 249

Superficial pain: A-delta fibers = thinly myelinated fibers * These sensations are conducted relatively fast, are accurately localized, and do not outlast the provoking stimulus * Humans - carried in spinothalamic tract Deep pain: C-fibers = thinner unmyelinated fibers * These fibers appears to be carried to the cerebral cortex by the ascending reticular formation and the spinothalamic tract (King)

Answer 250

C8-L4 (de Lahunta)

Answer 251

1. Immature (primitive neurons) or glioblasts * Migrate to the surface of the rhombic lip * Give rise to purkinje neurons and neurons of cerebellar nuclei 2. Actively dividing germinal layer cells * Continue to divide as they migrate to the surface of the rhombic lip = superficial layer called the external germinal layer * As the cerebellar folia develop, these germinal cells will remain on the external surface of these folia * Continue to divide until they have formed an external germinal layer that is 10-12 cells thick * The deeper layers stop dividing and differentiate into immature neurons --\> migrate deeper past Purkinje cells --\> granule cell neurons of the granular layer * Also creates the stellate (interneurons) of the molecular layer (de Lahunta)

Answer 252

1. Molecular * Axons and telodendria of granule cell neurons * Dendritic zones of the Purkinje neurons * Small population of interneurons and astroctytes 2. Purkinje * Purkinje cell bodies 3. Granular * Granule neuron cell bodies * Golgi cell (between Purkinje and granular layer) (de Lahunta)

Answer 253

Single layer of ependymal cells that form the lining of the 4th ventricle (de Lahunta)

Answer 254

Purkinje neurons are formed by differentiation of rhombic lip germinal cells early in embryonic development * The entire population is differentiated over just a few days * They grow and mature as they migrate into the developing cerebellar parenchyma * The total population of Purkinje neurons is well established before the fetus is born The external germinal layer (becomes granule neurons, stellate neurons) - continues to divide into late gestation or after birth in some species (de Lahunta)

Answer 255

Brain-derived neurotrophic factor - mitogenic influence, chemotactic effect Radial astrocytes assist migration/maturation Leptomeninges adjacent to the folia play a role in organization of the cerebellar cortex - if leptomeninges are disrupted during development, the cortical layers will develop abnormally (de Lahunta)

Answer 256

Dog and cat - External germinal layer reaches maximum thickness until 1 week old, decreases in size after 2nd postnatal week * Poorly populated granule cell neuron layer is present at birth * Grows rapidly over the first few weeks --\> continues to grow for up to 10 weeks * External germinal layer cells persist for as long as 60-84 days in the kitten, 75 days in the puppy * When all the cells have migrated into the molecular layer and granular layers, only the leptomeninges remain on the surface of the folia Calf - External germinal layer reaches maximum thickness at 183 days gestation --\> slowly decreases in thickness --\> 2 cells thick by 2 mos old gone by 6 mos postnatally \*\* avoid confusing the external germinal layer in young animal with meningitis! (de Lahunta) Picture: 2-day old puppy: 1 – choroid plexus, 2 – cerebellar nucleus; thick external germinal layer covering the developing folia at the top of the image

Answer 257

1. Right cerebellar hemisphere 2. Caudal vermis 3. Uvula 4. Paramedian lobule 5. Uvulonodular fissure 6. Ansiform lobule 7. Nodulus 8. Dorsal paraflocculus 9. Ventral paraflocculus 10. Flocculonudular peduncle 11. Flocculus 12. Cerebellar peduncles 13. Lingula 14. Rostral vermis 15. Uvulonodular fissure (de Lahunta)

Answer 258

Aka vestibulocerebellum Flocculus = small lobule on the ventral aspect of the cerebellar hemisphere Nodulus = rostral part of the caudal vermis, adjacent to the 4th ventricle Flocculus and nodulus are connected by the flocculonodular peduncle

Answer 259

1. Ventral paraflocculus 2. Dorsal paraflocculus 3. Dorsal surface of cerebellum 4. Primary fissure 5. Vermis of the rostral lobe 6. Right cerebellar hemisphere 7. Vermis of the caudal lobe 8. Ansiform lobule (de Lahunta)

Answer 260

1. Stellate cell 2. Basket cell 3. Golgi cell 4. Granule cell Inhibitory neurons = broken line Facilitatory neurons = solid line

Answer 261

1. Mossy fibers * Exert their influence on Purkinje cells indirectly, by synapsing on granule cell neurons, Golgi cells, and basket cells 2. Climbing fibers * Exert their influence directly on Purkinje dendrites (both Mossy fibers and Climbing fibers are excitatory to their target cells) (Uemura)

Answer 262

Widespread origin (Pontine nucleus, vestibular nuclei, lateral cuneate nucleus, nucleus cuneatus, nucleus thoracicus) --\> cerebellum --\> cell bodies/dendritic zones of cerebellar nuclei (release ACh) Cerebellar nuclei --\> cerebellar medulla --\> white lamina of a folium --\> granular layer * Granule cells * The parallel fibers of granule cells in the molecular layer synapse adjacent Purkinje dendrites --\> excitatory to Purkinje cell --\> overall inhibitory influence (on cerebellar nuclei) * Granule cell has excitatory input on basket cells in the molecular layer --\> basket cells inhibit Purkinje cell BODY --\> disinhibition * Golgi cells * Mossy fibers provide excitatory input to Golgi cells --\> Golgi cell is inhibitory to granule cells --\> inhibitory to Purkinje cells --\> results in disinhibitory influence * "Golgi cells control the duration of firing of granule cells" "Granule cell parallel fibers, therefore, excite Purkinje cells in a specific plane, but inhibit Purkinje cells in a different plane" ACh is the neurotransmitter released (de Lahunta, Uemura)

Answer 263

Cell body in olivary nucleus --\> axons enter caudal cerebellar peduncle --\> collaterals synapse on cerebellar nuclei --\> main axons continue to the white lamina of a folium --\> molecular layer In the molecular layer: excitatory synapse on the dendritic zone of a Purkinje neuron ASPARTATE is the neurotransmitter released

Answer 264

Purkinje cell --\> axon passes throgh granular layer --\> folial white matter lamina --\> cerebellar medulla --\> majority terminate in cerebellar nuclei Small population of Purkinje neuronal axons (w cell body in the flocculonodular lobe) --\> caudal cerebellar peduncle --\> vestibular nuclei With the exception of these direct cerbellovestibular Purkinje neuronal projections, the efferent axons that project from the cerebellum to the brainstem are all from the cerebellar nuclei Purkinje cells all release GABA neurotransmitter (de Lahunta)

Answer 265

General proprioception: 1. Spinocerebellar tracts --\> caudal cerebellar peduncle (small group via rostral) 2. Cuneocerebellar tracts --\> caudal cerebellar peduncle Special proprioception 1. Vestibulocerebellar axons * Directly from CN 8 --\> cerebellum * Vestibular nucleus --\> caudal cerebellar peduncle Target location: cerebellar cortex of the vermal and paravermal lobules

Answer 266

1. Tectocerebellar axons --\> rostral cerebellar peduncle --\> head region of the vermis 2. Visual/auditory areas of the cerebral cortex --\> pons --\> pontine neurons --\> transverse fibers of the pons --\> middle cerebellar peduncle --\> cerebellum (de Lahunta)

Answer 267

1. Red nucleus --\> rubrocerebellar axons --\> rostral cerebellar peduncle 2. Reticulocerebellar axons --\> caudal cerebellar peduncle 3. Olivary nuclei * Extrapyramidal nuclei --\> olivary nuclei --\> cerebellum 4. Pontine nucleus * Cerebropontocerebellar pathway (de Lahunta)

Answer 268

Located in the ventrolateral caudal medulla Rostral margin: facial nucleus, Caudal margin: obex Ventral margin: Pyramid and medial lemniscus UMN system, spinal cord afferents --\> olivary nucleus --\> decussate --\> join contralateral caudal cerebellar peduncle Appearance of 3 fingers oriented obliquely

Answer 269

Vermal and paravermal lobule Receive sensory signals from the spinal cord --\> controls posture, locomotion and gaze * Proprioception from dorsal/ventral spinocerebellar, cuneocerebellar tracts --\> paraflocculus --\> interposital nucleus --\> * Rostral cerebellar peduncle --\> contralateral motor cortex * Caudal cerebellar peduncle --\> red nuleus, olivary nucleus * The paravermal zone and interposital nucleus influence the motor centers that give rise to the corticospinal and rubrospinal tracts * Proprioception from dorsal/ventral spinocerebellar, cuneocerebellar tracts --\> vermis --\> fastigal nucleus --\> * Contralateral cerebral motor cortex * Reticular formation * The circuit involving the fastigal nucleus, vermis, cerebral motor cortex, and reticular formation is essential for maintenance of posture and muscle tone (Uemura)

Answer 270

Lateral zone = hemispheric zone = cerebrocerebellum = pontocerebellum * Major site mediating cerebral afferents * Plays a role in planning and control of fine movements of the extremities * Cerebropontocerebellar loop * Motor cortex --\> internal capsule --\> crus cerebri --\> decussate transverse fibers of the pons --\> middle cerebellar peduncle --\> granular neurons --\> purkinje neurons --\> lateral cerebellar nucleus (dentate nucleus) --\> rostral cerebellar peduncle --\> ventral tegmental decussation --\> ventral lateral nucleus of the thalamus - ... -\> motor cortex (UMN, Uemura)

Answer 271

Activation of the medullary reticular formation --\> inhibition of GSE LMN --\> cataplexy * When activated, the pontine reticular formation releases ACh --\> facilitory to medullary reticular formation --\> results in cataplexy * The locus coeruleus (releases norepi) and dorsal raphe nucleus (releases serotonin) both inhibit the pontine reticular formation, thus preventing cataplexy * The ventrolateral nucleus of the hypothalamus releases hypocretin which is facilitory to the locus coeruleus and dorsal raphe nucleus * Light on the retina --\> CN2 --\> suprachiamic nucleus (hypothalamus) --\> stimulates ventrolateral nucleus of the hypothalamus to secrete hypocretin (de Lahunta)

Answer 272

Facilitation: physostigmine, acreoline Inhibitory: atropine, scopolamine, norepi, serotonin, imipramine An increase in cholinergic mechanisms or decrease in monoaminergic mechanisms will result in cataplexy - thus cataplexy may be explained by brainstem cholinergic hypersensitivity, monoaminergic hypoactivity, or a combination of both (de Launta)

Answer 273

True - influences the activity of cranial projecting sensory systems (de Lahunta)

Answer 274

Carnivores: overlaps with sensory area - postcruciate gyrus and rostral syprasylvian gyri Postcruciate gyrus - neurons --\> appendicular musculature Suprasylvian gyrus --\> cervical muscles, muscles of specific areas of the head Ungulates: medially along the frontal lobe in the region of the precruciate gyrus These areas may be arranged somatotopically Neuron cell bodies = giant pyramidal cells or Betz cells Located in lamina V of the cerebral cortex of the gyri that comprise the motor area (de Lahunta) Picture: Topography of the cerebral motor cortex. 1, Postcruciate gyrus: A, pelvic limb; B, thoracic limb. 2, Rostral suprasylvian gyrus: C, ear; D, eyelid; E, masseter, temporal muscles; F, lateral cervical muscles.

Answer 275

Neuron w/ cell body in the motor area of the cerebral cortex --\> corona radiata, centrum semiovale, internal capsule, crus cerebri, longitudinal fibers of the pons, pyramid of the medulla * 75% of these fibers decussate in the pyramid of the medulla --\> lateral funiculus as the **lateral corticospinal tract** * 50% of lateral corticospinal tract terminates in the cervical spinal cord gray matter * 20% in the thoracic spinal cord gray matter * 30% in the lumbosacral spinal cord gray matter They either synapse on interneurons --\> GSE LMN OR (specifically cell bodies within somesthetic cortex) --\> dorsal gray column neurons (de Lahunta)

Answer 276

Pyramidal neurons: * 75% decussate --\> lateral corticospinal tract * 25% do not decussate --\> ventral corticospinal tract * Ventral funiculus, adjacent to the ventral median fissure * Decussate in the ventral commissure --\> terminate in the midthoracic spinal cord segments * Except in cats - serves the entire spinal cord gray matter * Synapse on interneurons --\> gamma motor neuron OR dorsal horn \*\* Ungulates - entire pyramidal system is confined primarily to the cervical spinal cord segments (de Lahunta)

Answer 277

Pyramidal neurons in the motor area --\> ...... --\> crus cerebri --\> axons decussate and synapse on contralateral brainstem nuclei GSE LMN (all CN nuclei with GSE component) Also synapse on the reticular formation (de lahunta)

Answer 278

Most **l**ateral: **l**umbar intumescence (lateral lumbar) Middle: Cervical intumescence Medial: Corticonuclear (de Lahunta)

Answer 279

Stellate neurons = granular neurons Small round cell body and short processes that are usually confined to the cortex They are concerned with INPUT Pyramidal neuron - pyramid shaped cell body that varies in size and has long processes Axon of the pyramidal neuron projects from the cortex --\> association axon/commisural axon/projection axon Involved with OUTPUT (de Lahunta)

Answer 280

(outer --\> inner) 1. Molecular layer * Dendrites of pyramidal cells * Fibers of stellate cells * Afferent endings of projection fibers and association fibers 2. External granular layer * Stellate cells (axons confined to the cortex) - ramifying vertically (centripetally and centrifugally) and also horizontal * Small pyramidal cells - axons may terminate in the cortex 3. External pyramidal layer * Medium-sized pyramidal cells - apices point towards the surface, each giving rise to a thick apical dendrite that extends into the molecular angle * The lateral range of the pyramidal cells form shorter horizontal dendrites * Axons of the pyramidal cells are thinner than the main dendrites * Some of the axons of these pyramidal cells end in the deeper layers of the cortex, others enter the white matter but return to the cortex (association or commissural fibers) 4. Internal granular layer * Stellate cells (axons confined to the cortex) - ramifying vertically (centripetally and centrifugally) and also horizontal 5. Internal pyramidal layer (also called Ganglion layer) * Large-sized pyramidal cells * Similar morphology to layer III * Form corticofugal fibers * These project to the basal nuclei, brainstem nuclei and spinal cord (form corticospinal pathways) * Others are association fibers which leave the cortex and go to distant cortical regions 6. Multiform layer * Small nerve cells with axons that are distributed chiefly in the more superficial layers of the same or contralateral cortex

Answer 281

Extrapyramidal system (de Lahunta)

Answer 282

Extrapyramidal neurons are located in the cerebral cortex throughout the cerebrum - most are in the cortex of the motor area and adjacent gyri of the frontal/parieta lobes Axons project to basal nuclei or other extrapyramidal nuclei in the brainstem (de Lahunta)

Answer 283

1. **Se**ptal nuclei and **a**mygdala (limbic system) 2. **Ca**udate nucleus 3. **Cl**austrum 4. **Nu**cleus accumbens 5. **Le**ntiform (putamen/pallidum) "See a cat climb new ledges" (de Lahunta)

Answer 284

Nucleus accumbens

Answer 285

Endopeduncular nucleus Most obvious where it is positioned between the internal capsule and optic tract

Answer 286

Neocortical extrapyramidal neurons --\> caudate nucleus --\> pallidum --\> ventral rostral nucleus of the thalamus --\> neocortex At the time of cortical initiation of voluntary movement, this circuit provides a modifying control mechanism The ventral rostral thalamic nucleus is a projection nucleus for the extrapyramidal system

Answer 287

Globus pallidus It receives converging fibers from all the other basal nuclei and is the only component of the basal nuclei that sends projection fibers outside the basal nuclei themselves It exerts a mainly INHIBITORY influence on the reticular formation (King's)

Answer 288

1. Endopeduncular nucleus 2. Zona incerta 3. Subthalamic nucleus All 3 of these nuclei are connected to the extrapyramidal nuclei in the telencephalon and caudal brainstem by afferent and efferent axons. No axons project directly to the spinal cord (de Lahunta)

Answer 289

1. Substantia nigra 2. Red nucleus

Answer 290

Afferent axons from ipsilateral motor area of neocortex --\> internal capsule/crus cerebri --\> red nucleus in the mesencephalon Axons of the red nucleus immediately decussate in the tegmentum --\> descend caudally as the rubrospinal tract Found in the lateral funiculus of the spinal cord (closely associated with lateral corticospinal tract), extends the entire length of the spinal cord Axons terminate on interneurons of the ventral gray column of the spinal cord --\> facilitatory to flexor muscles --\> functions in the initiation of protraction of the limbs Also: RUBRONUCLEAR AXONS: leave red nucleus --\> decussate --\> terminate in CN nuclei with GSE LMN (de Lahunta)

Answer 291

The neurons in the thoracic limb --\> dorsal part of the red nucleus --\> contralateral thoracic limb muscles The neurons in the pelvic limb --\> ventral part of the red nucleus --\> contralateral pelvic limbs (de Lahunta)

Answer 292

Neurons of the neocortex --\> ipsilateral pontine nucleus --\> decussate transverse fibers of the pons --\> middle cerebellar peduncle --\> cerebellar cortex --\> cerebellar nucleus --\> rostral cerebellar peduncle --\> decussate in the tegmentum --\> red nucleus (ipsilateral to original cortical neurons) --\> thalamus (ventral rostral nucleus) --\> neocortex

Answer 293

Caudate nucleus Dopamine synthesized in the substantia nigra and secreted at the caudate nucleus = nigrostriatial system (de Lahunta)

Answer 294

1. Activates cerebral cortex 2. Induces sleep 3. Caudally projecting UMN control of GVE functions 4. Caudally projecting UMN control of GSE function - voluntary and involuntary motor activity (de Lahunta)

Answer 295

Postural phase * Pontine: + ipsilateral extensors * Vestibulospinal: + ipsilateral extensors Protraction phase: * Red nucleus: + contralateral flexors * Medullary: - ipsilateral extensors (de Lahunta)

Answer 296

Motor cortex --\> corticoreticular axons --\> internal capsule/crus cerebri --\> decussate @ reticular formation --\> medullary reticular nucleus --\> descends in ipsilateral lateral funiculus as medullary reticulospinal tract --\> inhibitory to extensors --\> pontine reticular nucleus --\> descends in ipsilateral ventral funiculus as pontine reticulospinal tract --\> facilitatory to extensors (de Lahunta)

Answer 297

Extrapyramidal nucleus in the medulla Located just dorsal to the rostral part of the pyramids The olivary nucleus is a main source of efferent information to the cerebellum via the caudal cerebellar peduncle Axons leave the olivary nucleus --\> decussate in the medulla while "intermingling" with the fibers of the medial lemniscus --\> caudal cerebellar peduncle --\> cerebellar cortex Cerebellar cortex --\> lateral cerebellar nucleus --\> rostral cerebellar peduncle --\> decussation of the rostral cerebellar peduncle --\> * Red nucleus --\> ventral rostral nucleus --\> cerebrum * ventral lateral nucleus --\> cerebrum Afferent information from: red nucleus, pallidum, zona incerta

Answer 298

Olivary nucleus - mediates efferents of the red nucleus to the contralateral cerebellum Pontine nucleus - mediates pyramidal efferents from the cerebral cortex --\> contralateral cerebellum (Uemura)

Answer 299

Originates in rostral colliculus --\> decussate in the midbrain --\> descends in the ventral funiculus and terminates on interneurons of the cervical spinal cord Function - turns head toward sudden auditory/visual stimuli (Big Miller)

Answer 300

1. Initiate voluntary activity of the motor system 2. Maintain muscle tone to support the body's weight against gravity, establish posture on which voluntary activity can be performed 3. Control the muscular activity associated with the visceral functions (respiratory, cardiac, excretory) (de Lahunta)

Answer 301

1. Nuclear bag - interrupted near its middle by nonstriated dilation containing most of the nuclei 2. Nuclear chain - no central dilation, most of its nuclei are accumulated near the middle of the fiber (de Lahunta)

Answer 302

Gamma efferent neurons: * Small myelinated neurons whose cell bodies are in the ventral gray horn of the spinal cord (alpha neurons are larger) * Gamma plate - terminate on the striated muscle fiber component of the nuclear bag intrafusal muscle fibers * Gamma trail - terminate on the polar areas of the nuclear chain striated intrafusal fibers Afferent neurons: * Group Ia afferent - annulospiral ending around nuclear bag region * Large axon, cell body in spinal ganglion * --\> synapse on alpha LMN -OR- are involved in cranial projection of GP pathways to the cerebellum/cerebrum * Group II afferent (flower spray endings) - innervate intrafusal muscle fibers on both ends (de Lahunta)

Answer 303

Tonic gamma loop: Gamma efferent input --\> contraction of intrafusal fibers --\> stretches nuclear bag region --\> stimulates 1a afferent annulospiral ending --\> DRG --\> (+/- interneuron) --\> ventral horn --\> alpha motor neuron --\> extensor muscle contraction This is responsible for maintaining normal muscle tone Phasic gamma loop/flexor reflex gamma loop: Gamma efferent input --\> contraction of intrafusal fibers --\> stimulates group II sensory neuron --\> DRG --\> (+/- interneuron) --\> ventral horn --\> flexor muscles Functions with UMN to initiate flexor reflexes in the generation of gait (de Lahunta)

Answer 304

Increase in muscle strength --\> muscle spindle fires It's motor innervation maintains the length of the stretchable mid region close to the threshold of its annulospiral receptor Further elongation of the mid region --\> receptor fires (rate of firing related to the increase in length)

Answer 305

Golgi tendon organs are receptors within tendons that house the dendritic zones of 1b sensory neurons * 1b sensory neurons have a HIGHER stretch threshold to firing when compared to 1a neurons * Tendon stretched --\> contraction of extrafusal fibers in the muscle --\> 1b sensory neurons stimulated * 1b sensory neurons synapse at the ventral gray horn --\> inhibitory to the GSE alpha motor neurons innervating the contracting muscle * Synapse on interneurons that are facilitatory to the GSE alpha motor neurons innervating antagonistic muscles * Called the "inverse myotactic reflex" - prevents overstretching tendons

Answer 306

Outer (scleral) to inner (vitreal) 1. Pigment epithelium - single layer of cuboidal cells * Processes of the apical membrane interdigitate with processes of the external segments of the photoreceptors * Role - regeneration of rhodopsin, removal of degenerate rod membranous lamellae * Melanin granules fill apical cytoplasm 2. Photosensitive layer * Dendritic zone and cell body of the SSA neuron (photoreceptor cell) * External segment - parallel lamellae of the rods and cones * Rods - rhodopsin, cones - idopsin 3. External limiting membrane * Junctional complexes between photoreceptor neurons and supporting radial astrocytes (Muller cells) 4. External nuclear layer * Composed of the nuclei of the cell bodies of the photoreceptors = SSA neurons 5. External plexiform layer * Axons and telodendria of the photoreceptor neurons * Axons and dendritic zones of the bipolar neurons * Processes of horizontal neurons (interneurons between photoreceptors) 6. Internal nuclear layer * Nuclei in the small cell bodies of the bipolar neurons * Bipolar neurons: connect photoreceptor neurons with ganglionic neurons in the visual pathway * Cell bodies of horizontal interneurons * Cell bodies of amacrine interneurons * Nuclei of radial astrocytes 7. Internal plexiform layer * Axons and telodendria of the bipolar neurons * Axons/dendritic zones of ganglionic neurons * Processes of amacrins interneurons 8. Ganglion layer * Cell bodies of ganglion neurons 9. Nerve fiber layer * Axons of the ganglionic axons, unmyelinated until they penetrate the sclera at the optic disc (area cribrosa) 10. Internal limiting membrane * Layer of radial astrocytes * Basmement membrane adjacent to vitreous

Answer 307

Dark: * Photoreceptors have cGMP-gated Na+ channels in the outer segment membrane * In the dark - cGMP is high within the photoreceptor cell --\> binds to Na channels --\> opens channel --\> depolarization --\> release of glutamate on bipolar and horizontal cells * Rods/cone cells only generate receptor potentials, not action potentials (Uemura)

Answer 308

* Light stimulates rhodopsin/iopsin --\> activation of transducin (GPCR) * Transducin stimulates cGMP phosphodiesterase --\> hydrolyzes cGMP * Reduced intracellular cGMP --\> closes cGMP Na channels --\> hyperpolariztaion of photoreceptor cell --\> reduced release of glutamate (Uemura)

Answer 309

Cone cells - 2 opsins Pigment sensitive to light with a wavelength of either violet (429 - 435nm), or yellow-green (555nm) Rods have rhodopsin as their photopigment - low threshold of excitability Cones have idopsin as their photopigment - higher threshold of excitability 95% of photoreceptor cells are rods (Uemura)

Answer 310

Photoreceptors tear away from the pigment epithelium --\> results in degeneration of the photoreceptors Many rods converge on one bipolar neuron One cone converges on one bipolar neuron Many bipolar cells converge on one ganglion cell (de Lahunta)

Answer 311

Neurons with the smallest cell bodies --\> axons that project to the **rostral colliculus** Neurons with the larger cell bodies --\> axons project to the **lateral geniculate nucleus** Suggests a greater projection from the lateral retina (medial visual field in space) to the lateral geniculate nucleus of the thalamus for cerebral projection (de Lahunta)

Answer 312

* An increase in the number of cone cells relative to rod cells is found in the photosensitive layer * With an overall increase in thickness of the external nuclear layer * The length of the external segments of the photoreceptor cells is also increased * Bipolar and ganglionic neurons in this area are increased in number (de Lahunta)

Answer 313

Toy breeds - optic disc usually completely in the nontapetum Medium sized breed - optic disc usually halfway over the the interior border of the tapetum Large breed - optic disc entirely over the tapetum Dog - Myelination of the optic nerve fibers at the optic disc. Veins form a venous circline on the surface of the optic disc Cat - the optic disc (on fundic exam) is rounder and darker, owing to lack of myelination. It is always located over the tapetum The veins stop at the disc margin and do not cross its surface The arteries of the feline retina are fewer and less tortuous compared with those in the canine retina (de Lahunta/Slatter)

Answer 314

Each optic tract contains axons mostly from the MEDIAL retina of the contralateral eyeball, and the LATERAL side of the ipsilateral eyeball (deLahunta)

Answer 315

Optic radiation (de Lahunta)

Answer 316

1. Caudal marginal gyri 2. Ectomarginal gyri 3. Occipital gyri 4. Splenial gyri MNEMONIC: SOME The visual pathway is somatotopic - specific anatomic portions of the retina are represented in specific anatomic portions of the optic tract, lateral geniculate nucleus, optic radiation, visual cortex (de Lahunta)

Answer 317

1. Opposite cerebrum (via corpus callosum) 2. Motor cortex of both cerebral hemispheres 3. Cerebellum (via pons) 4. Rostral colliculus 5. Mesencephalic tectum --\> CN 3, 4, 6 6. Directly to CN 3, 4, 6 (de Lahunta)

Answer 318

80% --\> LGN --\> vision 20% --\> pretectal nucleus/rostral colliculus --\> reflexes (de Lahunta)

Answer 319

1. Tegmentum and medulla --\> GSE LMN 3, 4, 6 2. Tectospinal tract (decussates in the midbrain --\> ventral funiculus --\> Cspine) 3. Thalamus (tectothalamic axons) --\> feedback to the cerebral cortex 4. Cerebellum (tectocerebellar axons) --\> rostral cerebellar peduncle All of these pathways function in the coordination of head, neck and eyeball movements (de Lahunta)

Answer 320

1. Geniculate ganglion of the facial nerve 2. Distal ganglion of the glossopharyngeal nerve (located in the jugular foramen) 3. Proximal and distal ganglion of the vagus nerve - located ventromedial to the tympanic bulla 4. Dorsal root ganglion of spinal nerves (de Lahunta)

Answer 321

Middle ear, blood vessels of the head --\> facial nerve --\> geniculate ganglion of CN 7 Caudal tongue, pharynx, carotid body and carotid sinus --\> glossopharyngeal nerve (distal ganglion of CN 9 & 10) (de Lahunta)

Answer 322

"In general, GVA fibers accompany GVE fibers that originate from the same cord segments to innervate their target visceral structures" Nerve fibers of the cardiac and pulmonary plexus (GVE pathway involves middle cervical ganglion, cervicothroacic ganglion) - these plexuses also carry fibers from the vagus nerve innervating the heart, trachea, and lungs --\> fibers of the cardiac and pulmonary plexus reach the spinal cord via the sympathetic trunk Thoracic (greater) and lumbar splanchnic nerves: Arise from the sympathetic trunk --\> abdominal and plevic viscera Also carry GVA fibers to the sympathetic trunk (de Lahunta)

Answer 323

1. Stretch 2. Distention 3. Pressure 4. Chemical changes (de Lahunta)

Answer 324

Solitary tract * Cell bodies in facial ganglion, distal ganglion of CN 9 and 10 --\> axon enters the medulla --\> courses rostrally in the solitary tract --\> synapse in the solitary nucleus (de Lahunta)

Answer 325

1. Projects to neuronal cell bodies in the GVE and GSE system (directly or indirectly via interneurons of the reticular formation) * Nucleus ambiguus --\> swallowing * Parasympathetic nucleus of the vagus nerve --\> visceral organs * Parasympathetic nucleus of glossopharyngeal nerve --\> pharynx/palate 2. Reticular formation --\> visceral reflex centers (cardiac, swallowing, respiratory, coughing, vomiting) 3. Projects to the area postrema * (located adjacent to the floor of the 4th ventricle, abundance of small capillaries and glial cells) 4. Solitarothalamic pathway - travels on the contralateral brainstem, adjacent to the medial lemniscus and spinothalamic pathway * Ventral caudal medial nucleus of the brainstem --\> sensory neocortex (de Lahunta)

Answer 326

1. Respiration 2. Cardiovascular 3. Swallowing 4. Micturition (de Lahunta)

Answer 327

Regions that lack BBB 1. Area postrema 2. Subfornical organ - caudal surface of the columns of the fornix 3. Subcommissural organ - projects ventrally into the rostral mesencephalic aqueduct, ventral to the cadal commissure 4. Pineal gland 5. Hypothalamic vascular organ

Answer 328

Receptor in thoracic/abdominal viscera --\> branches of thoracic sympathetic trunk and abdominal splanchnic nerves --\> sympathetic trunk --\> ramus communicants --\> segmental spinal nerve --\> axon continues over the dorsal root --\> spinal cord @ dorsolateral sulcus --\> terminates in dorsal gray horn Reflex pathway: dorsal gray horn --\> dorsal gray column interneuron passes into adjacent intermediate gray horn in segments T1-L4--\> preganglionic sympathetic GVE neuron located there Conscious perception: dorsal gray horn --\> axon joins ipsilateral or contralateral lateral funiculus --\> spinothalamic tract --\> multisynaptic pathway that follows the same course as the spinothalamic system --\> * Ascending reticular activating system * Ventral caudal lateral thalamic nucleus --\> projection to sensory neocortex (Uemura)

Answer 329

Visceral nociception is referred to the surface of the body innervated by GSA neurons whose axons terminate in the same spinal cord segment and on the same neuronal cell bodies as the GVA neurons from a viscus Thus a dermatomal distribution of referred visceral pain exists - the surface of the body can be mapped to represent these areas of pain ex/ diaphragm referred to region of C5, 6, 7 (shoulder/neck) (de lahunta)

Answer 330

Taste bud consisting of supporting cells and neuroepithelial cells, arranged so that shorter cells are centrally located Centrally-located taste pore In the taste pore, the hair-like process is sensitive to chemical substances dissolved in the saliva There is rapid turnover of neuroepithelial receptor cells in the taste bud Rostral 2/3 --\> trigeminal branches --\> close to medulla join branches of CN VII (major petrosal and chorda tympani) --\> geniculate ganglion of the facial nerve Caudal 1/3 --\> glossopharyngeal nerve (de Lahunta)

Answer 331

SVA receptors of the pharynx/larynx (and cranial trachea) --\> cranial laryngeal of CN X --\> distal vagal ganglion Mediates the cough reflex (Uemura)

Answer 332

Archipallium + paleopallium = rhinencephalon = smell brain The olfactory portion of the rhinencephalon = paleopallium Nonolfactory rhinencephalon = archipallium (de Lahunta)

Answer 333

Bipolar neuron located in the olfactory epithelium of the nasal mucosa (caudal nasal cavity) * It is a specialized chemoreceptor * Olfactory epithelium = nasal mucosa that covers the ethmoid labyrinth * Its cell body and dendritic zone lie within the epithelium * 6-8 cilia project from the apex of the olfactory cell and lie in the secretions on the surface of the olfactory epithelium * They are stimulated by chemical substances dissolved in the secretions (de Lahunta)

Answer 334

Olfactory receptor --\> unmyelinated axon courses caudally from the cell body --\> connective tissue of the nasal mucosa --\> joins with other axons to form olfactory nerves Nerves pass through the foramina of the cribriform plate of the ethmoid bone --\> olfactory bulbs --\> synapse with brush cells and mitral cells The synapse of olfactory nerve cells + brush cells or mitral cells - called gomeruli At this point multiple olfactory neurons converge on a few neurons of the olfactory bulb Axons of brush and mitral cells of the olfactory --\> caudally on the surface of the olfactory peduncle - form medial and lateral olfactory tracts (de Lahunta)

Answer 335

Cell body: brush and mitral cells of the olfactory bulb --\> caudally on the surface of the olfactory peduncle --\> continued as lateral olfactory tract --\> ipsilateral olfactory cortex (surface of the piriform lobe) --\> synapses here with neurons in the cortex of the olfactory peduncle or olfactory tubercle Olfactory tubercle = nucleus between the medial and lateral olfactory tracts (de Lahunta) Figure 16.4 Anatomy of the special visceral afferent olfactory system. A, Amygdala; CLRS, caudal lateral rhinal sulcus; LOT, lateral olfactory tract; MB, mamillary bodies; MOT, medial olfactory tract; OB, olfactory bulb; OP, olfactory peduncle; OT, olfactory tubercle; PHG, parahippocampal gyrus; RLRS, rostral lateral rhinal sulcus; RMRS, rostral medial rhinal sulcus.

Answer 336

Ipsilateral WITHOUT relay through a thalamic nucleus Olfactory peduncle = olfactory axons (surface) + olfactory cortex (ventral to the medial and lateral rostral rhinal sulci) (de Lahunta)

Answer 337

Olfactory bulb --\> medial olfactory tract --\> rostral commissure --\> contralateral medial olfactory tract --\> contralateral olfactory bulb Piriform lobe --\> commissural axons pass in the rostral commissure --\> contralateral piriform lobe This is the "conscious perception" pathway (de Lahunta) Figure 16.4 Anatomy of the special visceral afferent olfactory system. A, Amygdala; CLRS, caudal lateral rhinal sulcus; LOT, lateral olfactory tract; MB, mamillary bodies; MOT, medial olfactory tract; OB, olfactory bulb; OP, olfactory peduncle; OT, olfactory tubercle; PHG, parahippocampal gyrus; RLRS, rostral lateral rhinal sulcus; RMRS, rostral medial rhinal sulcus.

Answer 338

Involve projections to the nuclear areas of the limbic system (without synapsing to the piriform cortex) Medial olfactory tract --\> septal area (septal nuclei and subcallosal area) --\> medial forebrain bundle: * Hypothalamus * Reticular formation --\> Parasympathetic nucleus of 7, 9, 10 --\> salivation and gastric secretion Lateral olfactory tract --\> amygdaloid nucleus and hippocampus (de Lahunta/King)

Answer 339

Olfactory binding protein - protein that is secreted by nasal mucosa. Thought to carry and/or concentrate odorant molecules The olfactory binding protein carries odorant molecules to the cilia of the olfactory sensory neurons A receptor odorant complex activates a G-protein --\> leads to activation of second messenger systems, opening of Ca2+ channels, and depolarization of the cilia This depolarization is conducted to the axon hillock of the olfactory sensory neuron, where action potentials are generated @ the olfactory bulb, olfactory sensory neuron is believed to secrete a peptide neurotransmitter (Uemura)

Answer 340

Hypothalamus Periaqueductal gray (Uemura)

Answer 341

Baroreceptors are located in the **carotid sinus and aortic arch**, and respond to changes in **blood pressure** Chemoreceptors are located in the **carotid body** and are sensitive to changes in **PaO2 and PaCO2** GVA fibers from the carotid body baroreceptor and carotid sinus chemoreceptor travel with the glossopharyngeal nerve --\> CNS GVA fibers from the aortic body baroreceptor --\> CN X \*\* Solitary nucleus --\> CN X + hypothalamus - HR/BP adjusted (Uemura)

Answer 342

Parasympathetic nerves - carry signals primarily from physiologic receptors Sympathetic nerves - carry signals mainly from nociceptors (Uemura)

Answer 343

Pelvic nerve Located on the lateral wall of the distal rectum GVA fibers --\> pelvic ganglia, communicating branches, dorsal roots --\> sacral spinal cord --\> terminate on sacral parasympathetic nucleus (lateral gray horn), or join the spinothalamic tract to project visceral pain to the cerebrum via the thalamus

Answer 344

1. Olfactory bulb 2. Olfactory peduncle (olfactory tracts + olfactory tubercle) 3. Cortex of the piriform lobe Rhinencephalon = paleopallium + neopallium (hippocampus) (de Lahunta)

Answer 345

Main 4: 1. Cingulate gyrus 2. Hippocampus 3. Septal area 4. Amygdala Arranged in 2 incomplete ring-like structures on the medial aspect of the cerebral hemisphere, at its border with the diencephalon Inner ring: 1. Amygdaloid body 2. Hippocampus 3. Fimbria-fornix: septal area, hypothalamus, mamillary bodies Outer ring: 1. Cingulate gyrus and cingulum 2. Septal area 3. Medial forebrain bundle + hypothalamus 4. Brainstem GVE LMN (not sure why included with telencephalon) (de Lahunta)

Answer 346

Amygdaloid body is one of the basal nuclei of the telencephalon. It is "buried deeply in the piriform lobe" Function: wide range of autonomic, endocrine, and somatic motor responses associated with emotion Efferent: * Stria terminalis --\> courses between the thalamus and caudate nucleus --\> rostral hypothalamus (major) and septal area (minor) * Diagonal band --\> connects the amygdaloid body with the septal area - courses on the ventral surface of the cerebrum Afferent: lateral olfactory tract, areas of the neocortex, thalamus, rostral hypothalamus, hippocampus, nucleus of the solitary tract (de Lahunta)

Answer 347

Dorsal to the caudal thalamus At the level of the rostral mesencephalic aqueduct (de Lahunta)

Answer 348

Hippocampal formation: 1. Hippocampus - long, curved nuclear mass * Connections to the cingulate gyrus and hypothalamus 2. Dentate gyrus - medial to the hippocampus, projects efferents to the hippocampus 3. Subiculum - between the lateral edge of the hippocampus and the medial edge of the parahippocampal girus * The entorhinal cortex of the parahippocampal gyrus is continuous with the subiculum --\> continuous with the hippocampus Efferent fibers: * Efferent fibers of the dentate gyrus project to the hippocampus * Efferent fibers of the hippocampus and subiculum form the fornix --\> projects to the hypothalamus * Subicular fibers of the fornix terminate in the hypothalamus and thalamus * Hippocampal fibers of the fornix terminate primarily in the mammillary nuclei of the hypothalamus (Uemura)

Answer 349

Hippocampus (King's)

Answer 350

* The fornix is made of fibers that leave the hippocampus as the **fimbria** * The 2 crura meet **rostral** to the hippocampal commissure and continue as the **body of the fornix** * Axons of the fornix body turn ventrally at the rostral commissure --\> **columns of the fornix** * Small bundle --\> rostral to the rostral commissure in the septum pellucidum --\> septal area * (confused if this is actually considered column of fornix) * Larger bundle --\> caudal to the rostral commissure --\> thalamus and mamillary body * The columns of the fornix form the rostral border of the interventricular foramen on each side * Caudal border of the interventricular foramen = choroid plexus (leptomeninges associated with choroid plexus here) (de Lahunta)

Answer 351

Septum pellucidum * Connects the body of the fornix (and the proximal portion of each column) to the corpus callosum * Caudal portion of this septum is not visible unless the lateral ventricle is enlarged * Rostrally, the septum pellucidum contains neuronal cell bodies of the septal nucleus

Answer 352

Cingulum * The cingulum is the corona radiata of the cingulate gyrus (de Lahunta)

Answer 353

Cingulate gyrus * Bound by the genual sulcus and the splenial sulcus (Uemura)

Answer 354

1. Subcallosal area * Cerebral cortex ventral to the genu of the corpus callosum 2. Septal nuclei * Collection of neuronal cell bodies in the rostral septum pellucidum that bulges into the medial side of the lateral ventricle * Dosal and just rostral to the bend in the body of the fornix Afferent: 1. Hippocampus (via columns of the fornix) 2. Amygdaloid body (via diagonal band and stria terminalis) 3. Olfactory bulb --\> medial olfactory tract Efferent 1. Median forebrain bundle --\> hypothalamus 2. Stria habenularis --\> habenular nuclei 3. Columns of fornix --\> hippocampus (de Lahunta)

Answer 355

1. Epithalamic habenular nucleus * Septal area --\> stria habenularis --\> habenular nucleus * Connects to the mesencephalon (habenulointercrural tract) 2. Rostral thalamic nuclei * Mamillary body of the hypothalamus --\> mammilothalamic tract --\> rostral thalamic nucleus * Rostral thalamic nuclei --\> cingulate gyrus and adjacent neopallium 3. Hypothalamus (Mamillary body) * Connects to mesencephalic tectum, visceral motor nuclei in the medulla, mesencephalic intercrural nucleus (de Lahunta)

Answer 356

Intercrural nucleus * Located ventrally, adjacent to the intercrural fossa between the crus cerebri * Connects to the habenular nucleus, mammillary body, reticular formation of the brainstem (de Lahunta)

Answer 357

Habenular nuclei: Participates in autonomic responses to olfactory and emotional stimuli (Kings)

Answer 358

Made of the 1. Cingulate gyrus 2. Hippocampal formation 3. Mammillary nuclei of the hypothalamus 4. Thalamus Efferents of the neocortex --\> cingulate gyrus --\> hippocampal formation --\> fornix --\> mammillary nuclei --\> mammilothalamic tract --\> thalamus --\> cingulate gyrus Red = Papez Circuit (Uemura)

Answer 359

1. Intercrural nucleus 2. Septal area 3. Rostral hypothalamus Self stimulation of these regions by cats and rats was sought so actively that the animals continually pressed the bar and did not eat Pain centers: Similar stimulation of the lateral hypothalamus and selected mesencephalic areas resulted in complete avoidance of the source of the stimulus (de Lahunta)

Answer 360

1. Cingulate gyrus 2. Amygdaloid body 3. Hippocampus Amygdalectomy = unfriendliness, fear, rage

Answer 361

* Dentate gyrus * 3 layered archicortex - molecular cells, granular cells, polymorph cells * Embedded into the concavity of the hippocampus proper * **Hippocampus proper** * **Gyrus folded concave medially** * **Archicortex is composed of 3 major layers** * **Molecular** * **Double pyramidal cells** * **These axons run in the fornix** * **Join alveus --\> continue as fimbria --\> crus of fornix, body of fornix, column of fornix (see below)** * **Polymorph cell layer** * **Divisible into 4 zones: CA1 (at the subiculum) --\> CA4 (at the dentate gyrus)** * Subiculum * Composed of variable layers * Major source of hippocampal output to the adjacent entorhinal cortex of the piriform lobe and parahippocampal gyrus

Answer 362

1. Rostral thalamic group (limbic system) 2. Medial thalamic (medial dorsal nucleus) 3. Lateral thalamic group * Dorsal * Dorsolateral nucleus * Caudolateral nucleus * Pulvinar nucleus * Ventral * Ventral rostral nucleus (extrapyramidal) * Ventral lateral nucleus (cerebellum) * Ventral caudal group * Ventral caudal medial nucleus (cranial nerves) * Ventral caudal lateral nucleus (spinal nerves) 4. Caudal thalamic group (metatlalamus) * Medial geniculate nucleus (auditory, vestibular) * Lateral geniculate nucleus (vision) 5. Intralaminar thalamic group * Central medial nucleus * Paraventricular nucleus 6. Thalamic reticular nucleus (ARAS) Internal medullary lamina - Divides each side of the thalamus into medial and lateral halves External medullary lamina - defines the external boundary of the lateral half of the thalamus. It is separated from the internal capsule by the narrow thalamic reticular nucleus

Answer 363

1. Direct cortical projection system - relay of sensory information and motor systems 2. Diffuse cortical projection system - thalamic association system that receives only axons from other diencephalic nuclei and telencephalic sources 3. Thalamic reticular system - most rostral component of the ARAS (de Lahunta)

Answer 364

Thalamic nuclei concerned with this function are located in the lateral half/ventral tier of the thalamus and in the caudal thalamic group 1. Ventral caudal lateral nucleus * GSA/GVA --\> spinothalamic tract --\> ventral caudal lat nucleus * GP --\> medial lemniscus --\> VCL nucleus * Neck, trunk, limbs --\> somesthetic cortex 2. Ventral caudal medial nucleus * GSA/GP from CN V --\> quintothalamic tract --\> ventral caudal medial nucleus * GVA, SVA --\> solitarothalamic tract --\> VCM nucleus * Head region --\> somesthetic cortex 3. Lateral geniculate nucleus * Optic tract --\> LGN --\> visual cortex of the occipital lobe 4. Medial geniculate nucleus * SSA (auditory) and SP (vestibular) --\> brachium of the caudal colliculus --\> medial geniculate nucleus --\> temporal lobe These nuclei also project to other thalamic nuclei (de Lahunta)

Answer 365

1. Ventral rostral nucles * Pallidum and red nucleus --\> ventral rostral nucleus --\> motor cortex of the parietal lobe 2. Ventral lateral nucleus * Cerebellar nuclei --\> rostral cerebellar peduncle --\> ventral lateral nucleus --\> motor cortex of the frontoparietal lobe * Red nucleus --\> ventral lateral nucleus --\> motor cortex of the frontoparietal lobe These nuclei also project to other thalamic nuclei

Answer 366

Diffuse cortical projection system No primary afferent sensory input to this system: Afferent: * Primary relay thalamic nuclei (involved in GSA/GVA/SSA/pyramidal/extrapyramidal relay) * Thalamic reticular system nuclei * Hypothalamus * Cingulate gyrus * Frontal cortex * Striatum Efferent --\> diffusely to the telencephalon Nuclei: 1. Rostral thalamic group 2. Medial group 3. Lateral group - dorsal tier (de Lahunta)

Answer 367

1. Intralaminar nuclei 2. Thalamic reticular nucleus Afferents: Reticular formation in the caudal brainstem, GSA/GVA conscious pathways Efferents: Thalamic nuclei of the diffuse cortical projection system This is the most rostral part of the thalamus it does NOT project directly to the cerebrum! influences the cerebrum indirectly via the diffuse cortical projection system (de Lahunta)

Answer 368

1. Rostral region (chiasmic group) 1. Supraoptic nucleus 2. Suprachiasmic nucleus 3. Paraventricular nucleus 4. Rostral hypothalamic nucleus 5. Preoptic nuclei 6. Rostral periventricular nucleus 2. Intermediate region (tuberal group) * Dorsomedial, ventromedial nuclei * Infundibular nucleus * Lateral hypothalamic area 3. Caudal region, mamillary group * Premammillary nucleus * Dorsal and dorsocaudal hypothalamic areas * Lateral perifornical hypothalamic nuclei * Periventricular nucleus * Mamillary nuclei (de Lahunta)

Answer 369

1. Telencephalon (rhinencephalon) * Hippocampus --\> columns of the fornix --\> mammillary bodies * Precommissural fibers: hypothalamus --\> septal nuclei, preoptic nuclei, anterior hypothalamus * Postcommissural fibers: subiculum --\> mammillary nuclei * Septal area --\> medial forebrain bundle * Amygdaloid body --\> stria terminalis * Pallidum --\> pallidohypothalamic axons --\> hypothalamus 2. Diencephalon * "Numerous axons enter the hypothalamus from various thalamic nuclei" * Uemura - frontal cortex and cingulate gyrus --\> medidorsal nucleus of the thalamus --\> hypothalamus (thalamohypothalamic fibers) 3. Mesencephalon * Brainstem GVA and SVA --\> mammillary peduncle * Periaqueductal gray (de Lahunta)

Answer 370

1. Mamillary nuclei --\> * Mammilothalamic tract --\> rostral thalamic nucleus * Mamillotegmental tract --\> mesencephalic reticular formation (UMN) --\> brainstem and spinal cord GVE LMN 2. Paraventricular nucleus --\> dorsal longitudinal fasiculus axons --\> periaqueductal gray 1. Paraventricular nucleus --\> hypothalamomedullary tract and hypothalamospinal tract 3. Hypothalamo-hypophyseal tracts (de Lahunta)

Answer 371

Hypothalamo-neurohypophyseal system terminates on blood vessels in the neurohypophysis Hypothalamo-adenohypophyseal system terminates on blood vessels in the tuber cinereum and infundibulum Both systems consist of axons that provide a pathway for neurosecretory substances produced by neuronal cell bodies in the hypothalamus to access vessels (de Lahunta)

Answer 372

Oxytocin Vasopressin = ADH They are carried down the axons of the supraoptico-hypophyseal and paraventriculo-hypophyseal tracts to the neurohypophysis --\> released in the capillary bed and circulate to the effector organ Supraoptic nucleus: axons with ADH are more numerous than those carrying oxytocin (opposite is true for paraventricular nucleus) (de Lahunta)

Answer 373

Neurosecretory products involved with adenohypophyseal regulation pass through axons of the **tuberohypophyseal tract** --\> capillary plexus in the tuber cinereum and infundibulum --\> circulate via hypophyseal portal system to the sinusoids of the adenohypophysis to influence the endocrine activity of the cells in the **pars distalis** According to de Lahunta, these neurosecretory products are produced in "a variety of hypothalamic nuclei" Uemura - Suprachiasmic nucleus, medial preoptic nucleus, paraventricular nucleus, and arcuate nucleus release hormones into capillary network --\> adenohypophysis (de Lahunta)

Answer 374

Rage, aggression (Kings)

Answer 375

Septal nuclei (de Lahunta)

Answer 376

Neurons with a depressor effect on arterial pressure and heart rate are found in the central (medial) group of neurons in the reticular formation of the medulla Neurons with a pressor effect on arterial BP/HR found in the lateral group of neurons (Kings)

Answer 377

Medulla: Inspiratory center in the central region of the reticular formation Expiratory center in the lateral region of the reticular formation Pons: Pneumotaxic center - inhibits the inspiratory center of the medulla by negative feedback Apneustic center - steady excitatory drive to the inspiratory center Medullary respiratory center --\> reticulospinal tracts --\> C5, 6, 7 --\> interneurons --\> ventral horn neurons --\> phrenic nerve --\> diaphragm T1-T13 --\> interneurons --\> ventrla horn neurons --\> spinal nerves to the intercostal muscles (Kings)

Answer 378

Dog: T1-L5 Cat: T1-L2

Answer 379

Feeding center: Lateral hypothalamic nucleus Satiety center: ventromedial hypothalamic nucleus (Uemura)

Answer 380

1. Projection areas 1. Primary somatic sensory area 2. Visual area 3. Auditory area 4. Primary motor area 2. Rhinencephalon (olfactory and limbic) 3. Association areas 1. Become more important in mammals that are phylogenetically advanced (Kings)

Answer 381

Association areas The most common neurons in the association areas are cells with short axons, very widespread dendrites - these are virtually interneurons connected into a vast meshwork of nerve cells They are not confined to one layer or region of the brain Rabbit and rat - projection areas are 100% of the brain, association areas are 0% of the cortex Cat and dog - projection areas are 80% of the total area of the cortex, association areas are 20% Man - Projection areas are 15% of the total area of the cortex, association areas are 85% (Kings)

Answer 382

Instinct * Activated by a particular stimulus * Genetically determined * Anatomical site is difficult to identify, possibly hippocampus (Kings)

Answer 383

Neocortex - 6 layers * Primary cortex * Somesthetic I and II * Motor * Visual * Auditory * Association cortex Paleocortex - 3-5 layers * Entorhinal cortex of the parahippocampus * Endorhinal cortex of the piriform lobe * Cortex of the lateral olfactory gyrus (Uemura)

Answer 384

1. Postcruciate gyri 2. Rostral suprasylvian gyri 3. Rostral ectosylvian gyri (Uemura)

Answer 385

Phosphorylytic pathway (responsible for formation of glucose-6-phosphate Lysosomal hydrolytic pathway (VCNASAP Platt)

Answer 386

Pyruvate --\> inner mitochondrial membrane --\> TCA cycle If pyruvate cannot enter the TCA cycle because of a metabolic block, it may be shuttled either to lactate or alanine --\> hyperlactatemia or hyperalanemia (VCNASAP Platt)

Answer 387

1. Activation of fatty acids 2. Beta-oxidation of fatty acids --\> forms acetyl CoA --\> krebs cycle 3. Synthesis of triglycerides, phospholipids, and other fatty acid esters 4. Hydrolysis of lipid esters (VCNASAP Platt)

Answer 388

Derived from lysine and methionine Important in the transport of long-chain fatty acids into the mitochondria for beta oxidation Also forms esters with abnormal organic acids --\> excreted in the urine (VCNASAP Platt)

Answer 389

Should be measured as a screening test in all animals with suspected myopathic causes of weakness/collapse (especially if related to activity) Less ideal - pre and post-prandial lactate and pyruvate analysis can be performed when rest and subsequent exercise of the patient are not possible Lactate and pyruvate readily diffuse from working muscle - levels of these metabolites in venous blood can be used to monitor the integrity and level of activation of the energy pathways from which they arise Special tubes/collection methods. Delays \> 1h before deproteinization of samples --\> can induce major elevations in lactate/pyruvate ratios (VCNASAP Platt)

Answer 390

High serum lactate + pyruvate with normal LP ratio - defect in pyruvate dehydrogenase (or one of the gluconeogenic enzymes) Lactic acidosis + high LP ratio - defect in mitochondrial ETC OR pyruvate decarboxylase deficiency (VCNASAP Platt)

Answer 391

Organic acidurias - genetic inborn errors of metabolism Mitochondrial defects of beta-oxidation Alanine + hypoxanthine - readily diffuse from working muscle into venous blood They are markers of the integrity and level of activation of the energy pathways from which they arise (VCNASAP Platt)

Answer 392

Must look at urine, plasma, and muscle concentrations of total, free and esterified carnitine (via radioisotopic enzyme assay) Complex metabolic equilibrium exists for various carnitine and acylcarnitine fractions in various body compartments etc... (VCNASAP Platt)

Answer 393

Bregma (Miller's)

Answer 394

Nasion (Miller's)

Answer 395

Basion (Miller's)

Answer 396

1. CN 3 2. CN 4 3. Ophthalmic br of V 4. CN 6 5. External ophthalmic artery 6. Orbital venous plexus Orbital fissure is formed in the articulation between the basisphenoid and presphenoid bones Optic canal - passes through the orbital wing of the presphenoid bone

Answer 397

Caudal alar foramen: maxillary artery and vein Rostral alar foramen: maxillary artery and vein + maxillary br of V basisphenoid bone

Answer 398

Medially: saggital crest or temporal line Caudally: nuchal crest Ventrally: zygomatic process of the temporal bone Rostral: continuous with the orbit The temporal muscle arises from the temporal fossa on the frontal, parietal, and squamous temporal bones (Little Miller's)

Answer 399

1. Squamous - forms the caudal portion of zygomatic arch * Articulates dorsally with the parietal bone, rostrally with basisphenoid and presphenoid 2. Tympanic 3. Petrous (Little Miller's)

Answer 400

Frontal, lacrimal, sphenoid, presphenoid, and zygomatic bones Lateral margin = orbital ligament (frontal process of zygomatic bone to zygomatic process of frontal bone) (Little Miller's)

Answer 401

Located ventral to the orbit 1. Maxilla 2. Zygomatic bone 3. Zygomatic process of the temporal bone 4. Palatine bone 5. Pterygoid bone 6. Wings of the sphenoid bones Pterygoid muscles arise from this fossa (Little Miller's)

Answer 402

Caudal palatine foramen: major palatine artery, vein and nerve Sphenopalatine foramen: Sphenopalatine artery and vein, caudal nasal nerve (Little Miller's)

Answer 403

Basi-occipital bone * Articulates laterally with the tympanic and petrous parts of the temporal bone * Rostrally with the body of the basisphenoid * Caudally the occipital condyle articulates with the atlas (Little Miller's)

Answer 404

Digastricus (Little Miller's)

Answer 405

The **promontory** is a eminence on the ventral surface of the petrosal temporal bone that contains the **cochlear** window

Answer 406

Caudally with the basioccipital bone Rostrally with the presphenoid and pterygoid bones The oval foramen, round foramen, and alar canal are in the basisphenoid bone (Little Miller's)

Answer 407

The maxillary nerve leaves the calvarium through the **round** foramen and leaves the skull through the **rostral alar** foramen

Answer 408

Foramen lacerum "This loop is between the part of the internal carotid that is coursing rostrally in the carotid canal, and the part that returns through the foramen lacerum and enters the cavernous sinus on the floor of the cranial cavity" (Little Miller's)

Answer 409

Musculotubal canal Lies lateral to the foramen lacerum and caudal to the oval foramen (Little Miller's)

Answer 410

Tympano-occipital fissure * The petro-occipital canal and the carotid canal leave the depths of the fissure at about the same place * Carotid canal transmits the internal carotid artery * Petro-occipital canal transmits the ventral petrosal sinus * The glossopharyngeal, vagus, and accessory nerves course peripherally from the jugular foramen through the tympano-occipital fissure * Vessels: internal carotid artery, "venous radicles" of the vertebral and internal jugular veins * Also sympathetic postganglionic axons from the cranial cervical ganglion (Little Miller's)

Answer 411

Hypoglossal canal (Little Miller's)

Answer 412

Stylomastoid foramen Opening in the facial canal that conducts the facial nerve through the petrosal part of the temporal bone (Little Miller's)

Answer 413

Basoiccipital bone + basisphenoid bone + presphenoid The brain rests on the basicranial axis (Little Miller's)

Answer 414

1. Basilar membrane 2. Cochlear duct 3. Cochlear nerve 4. Inner tunnel 5. Modiolus 6. Organ of Corti 7. Osseous spiral lamina 8. Scala tympani 9. Scala vestibuli 10. Spiral ganglion 11. Spiral ligament 12. Spiral limbus 13. Spiral tunnel 14. Stria vascularis 15. Tectorial membrane 16. Temporal bone, petrous part 17. Vestibular membrane (Bacha Histology)

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