Week 1 Flashcards
(275 cards)
1
Q
What do large venous sinuses do for the CNS?
A
Act as fluid “cushions” to protect the delicate nervous tissues
2
Q
What is the ventricular system of the CNS?
A
Analogous to a plumbing system both within and surrounding the CNS. It contains clear, colorless fluid- the cerebrospinal fluid (CSF) which protects and nourishes the neuraxis
3
Q
What produces CSF? How many and where?
A
Choroid plexus which are in each of the four ventricles (all interconnected)
4
Q
What takes the CSF from the cerebellum into the subarachnoid space?
A
Lateral apertures under the cerebellum
5
Q
Where is the CSF in the spinal cord?
A
In the central canal
6
Q
What does the ventricular system develop from? And where is each part? Why is the ventricular system important?
A
It develops from the neural tube of the embryo. There is a different part of the ventricular system for each division of the brain. This helps identify the part of the brain on cross sections
7
Q
Name the meninges from external to internal
A
dura mater, arachnoid mater, and pia mater
8
Q
What is the epidural space? Where is there no epidural space?
A
External to the dura mater and contains fat and the vertebral venous lexis. It only exists around the spinal cord. It is obliterated in the mid cervical region, C3 (C2 to C4) by fusion of the dura with periosteum. The fusion begins ventrally and is completely circumferential by the level of the foramen magnum. NO epidural space within the cranium, however there is the potential e.g. haemorrhage after trauma (epidural haematoma)
9
Q
What is the dura mater?
A
- Dense, tough fibrous covering (composed of dense connective tissue with collagen fibres) that fuses with the periosteum of the cranial vault. - encloses the spinal roots as they leave the spinal cord and fuses with the epineurium at the intervertebral foramen.
10
Q
Where is the arachnoid mater not present?
A
Follows the larger contours and issues but not the absolute contours of the CNS. e.g. into the longitudinal issues but not the sulci
11
Q
What is the pia mater?
A
-Very delicate membrane which is fused to the contours of the CNS - subarachnoid space lies between the arachnoid and pia mater. It is filled with CSF. - arachnoid trabeculae are fine meningeal filaments that cross the arachnoid space between the arachnoid mater and the pia mater
12
Q
What is the falx cerebri?
A
The fold in the longitudinal fissure between the two cerebral hemispheres. Runs from the ethmoid bone to the osseous tantrum. Contains the dorsal sagittal venous sinus draining the dorsal forebrain.
13
Q
What is the tenorium cerebella?
A
Fold separating cerebral hemispheres from the cerebellum. Runs from the petrosal crest to the osseous tentorium, bilaterally. Inverted U, the midbrain passes through the notch along the ventral edge. - divides the cranial vault into: -the rostral fossa (rostral to the tentorium and contains the forebrain) - the caudal fossa (caudal to the tantrum and contains the cerebellum and the caudal brain stem). (often ossifies in cats)
14
Q
What is the diaphragm sella?
A
Bridges from the dorsal sella to the caudal cloned process of the sphenoid bones near the optic canal area. It can make removal of the entire brain, with pituitary intact, difficult.
15
Q
What occurs with brain herniation?
A
Movement of a portion of the brain under another structure. - the inelastic nature of the dural septa and the skull protect the normal brain, but compromise the diseased brain as they limits its ability to swell or adjust to expanding masses. - Swelling of the forebrain may cause herniation under the tentorium cerebella. - Swelling of the brain or any structure within the cranial vault may cause herniation through the foramen magnum
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Q
A
17
Q
What is the essential information in order to perform a neurological examination?
A
* organisation of the nervous system and hierarchy of control
* cranial nerve areas and types of innervation and function
* major peripheral nerves and areas of innervation and functions
18
Q
Essential information in order to interpret a neurological exam
A
* major structural organization of the spinal cord and brain (and tracts of the spinal cord) (what areas are most vulnerable?? what happens with a bulged disc??)
* Areas of origin of major nerves in the CNS and their function
* Paths of the cranial and peripheral nerves from the CNS to the area innervated
19
Q
Other important anatomical information for clinical diagnosis in neurological cases?
A
* Anatomy of the meninges and their associated spaces in brain and spinal cord
* Blood supply to brain and spinal cord
* Formation and resportion areas for CSF and where to sample
20
Q
Where are the cell bodies for the motor neurons? What about the sensory neurons? What are interneurons?
A
* Motor nerve cell bodies are in the CNS
* Sensory nerve cell bodies are outside- in a ganglion- not in the spinal cord
* Interneurons connect the two
21
Q
What is a reflex arc?
A
The simplest form of communication.
One step further- adding an interneuron
22
Q
Where is the sensory input? What is the motor output?
A
Sensory input- dorsal horn
motor output- ventral horn
23
Q
why is it that a chicken can still run around with it’s head cut off?
A
Animals with less developed brains, a lot of neurological control is a result of neurological pathways at the spinal level
Basically a series of reflexes!
24
Q
What reflex is for stability and postural support?
Mobility reflex?
A
Myotactic
Flexor withdrawal
25
What is an upper motor neuron?
\* UMN are motor neurons that originate in the motor region of the cerebral cortex or the brain stem and carry motor information down to the LMNs (efferents are in the spinal cord and synapse with LMNs or interneurons)
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What is a lower motor neuron? What are the levels of control of motor activity?
\* alpha motor neuron- final common pathway for motor control-- cell body in the spinal cord-- impacts on the muscle cell (efferents are alpha motor neurons i.e. supply muscle fibres)
27
What is meant by the motor system hierarchy?
Motor cortex= senior management
Interneurons in the spinal cord= junior management
Worker= alpha motor neuron- initiating the movement
28
What is a nucleus?
What is a ganglion?
\* Nucleus- Collection of nerve cell bodies inside the CNS- WHITE AND GRAY MATTER.
\* Ganglion- collection of nerve cell bodies outside of the CNS- i.e. autonomic ganglia, sensory ganglia
29
Name three nuclei in the brain stem
\* Red nucleus- rubrospinal tract
\* Vestibular nucleus- vestibulo-spinal tract
\* Reticular formation - reticulospinal tract
30
What does it mean to say brain stem pathways are EXTRA pyramidal?
Do not travel through the medullary pyramids
31
What provides most of the refined degree of motor control?
Primary motor cortex
32
What is the corticospinal tract? Are they pyramidal or extra-pyramidal?
Motor tract originating from the cerebral cortex. Pyramidal tract.
33
What does it tell us if a tract is pyramidal vs. extra pyramidal?
anatomical description. The tracts that go through the pyramids go through the cortex. Extra- pyramidal tracts go through the brain stem and are more important in animals with LESS DEVELOPED BRAINS.
34
What are funiculi?
Bundles of nerve fibers in the spinal cord
35
What is the hierarchy of control?
36
What is the function of the forebrain generally?
\* Perception of sensory input
\* Initiation of motor activity
\* integration/associaton of information
\* cranial nerves I and II
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What is the general function of the midbrain?
\* thoroughfare for ascending and descending information
\* major UMN nuclei for movement
\* cranial nerves III and IV
\* Consciousness (during anathesia rendered unconscious)
38
What is the function of the hindbrain?
\* Thoroughfare for ascending and descending information
\* major UMN nuclei for movement
\* coordination of muscle activity (cerebellum)
\* cranial nerves V to XII
\* regulation of many organ functions (cardiovascular, resp, gastrointestinal)
39
What is co transmission?
One neuron can release different neurotransmitters from different neuron processes (at one set of dendrites, compared to another). Also, that multiple neurotransmitters can be released from the same neuron process.
e.g. VIP and ACh depending on the frequency stimulation will release one or the other or both. they act as neuromodulators- which can affect the amount of release and the function. It is not just YES/NO- it depends on how much is released, frequency of impulses down the pre-synaptic nerve, and a feedback loop back to the pre-synaptic nerve
40
What are the steps of neurotransmission?
41
What are the different types of neuroreceptors?
42
What are the fast neurotransmitters in the CNS
\* Amino acids: glutamate, glycine, gamma amino butyric acid (GABA)
\* Acetyl choline
43
What are the slow neurotransmitters?
( slow "maranade"- important in memory, mood- changes slowly)
\* Acetyl Choline
\* Mono amines- dopamine, noradrenaline, 5 HT
\* NANC- histamine, purines (ATP)
\* Neuropeptides- endorphins, substance P
44
How do drugs target neurotransmitters?
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46
What is the notorchord?
Column of cells - develops the neural tube and neural crest cells
\*\* have to have the notochord to get development of the nervous sytem- one of the first to start developing but the last to finish (i.e. foal or calf walking straight away)
\*\* does not form the vertebral column- marks the future location of the vertebral column (bone comes from schleritome from the somites)
47
What is the ectoderm? Mesoderm? Endoderm?
48
What is neurulation?
\* The initial development of the gut, heart, and formation of the nervous system
\* ectoderm above the notochord thickens to form neural plate
49
What is the neural groove?
Midline depression due to thickening of the neural ectoderm
50
What are somites?
Age an embryo by the number of somites that are there
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What are neuroepithelium?
Cells lining the neural tube
\* Neuroepithelium produces all neurons
\* cells migrate from there to form neural crest
\*neural crest cells form the peripheral ganglia
\* rostral end forms the brain and the rest of the neural tube forms the spinal cord
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What are the plates here? What does the mantle layer differentiate into?
55
What are the three parts of somites?
(somites split and peripheral nerve migrates between)
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57
Why is there bending and folding as the brain develops?
Because it is occuring inside the skull.
58
What are the ventricles and what part of the brain are they developing from?
59
What ventricle is in the myelencephalon?
Fourth ventricle
60
What happens with development in the metencephalon?
Still in the hindbrain, becomes more complicated.
61
What level of the brain is developing here?
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What happens to the midbrain in a developed brain?
Forebrain "flops" over the midbrain
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Venous drainage of the brain
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choroid plexus
71
What is cerebrospinal fluid?
An ultrafiltrate of blood. Mostly produced by the choroid plexus which develops where the ependyma is in direct contact with the pia mater on the wall of each ventricle. The choroid plexus epithelium is actively involved in numberous exchange processes in both directions as well as other processes involved in brain homeostasis.
72
Main arteries to the nervous system
73
What are the two cerebral hemispheres?
What is the ventricular system?
Cerebellum and the brain stem
The ventricular system is an expansion of the spinal cord.
74
What produces the CSF? Where? How does CSF flow?
Produced by the choroid plexus within the ventricles
Flows rostral to caudal and then out into the subarachnoid space and flow gradually down beside the spinal cord
75
What are the 12 cranial nerves?
I olfactory
II optic
III oculomotor
IV trochlear
V trigeminal- mandibular, maxillary, ophthalmic
VI abducens
VII facial
VIII vestibulocochlear
IX glossopharyngeal
X vagus
XI accessory
XII hypoglossal
"On Old Olympus' Towering Tops A Fair Voluptuous German Vaulted And Hopped"
76
What happens when the CSF is at a higher pressure then the venous system?
The little balloons bulge out and you get reabsorption of the CSF into the venous system. If the production of CSF drops or pressure drops for any reason, then balloons collapse. As long as the venous pressure is lower, you get circulation and reabsorption back into the venous sinuses.
77
What happens at the intercostal foramina?
Nerves and blood vessels travel through. More potential CSF reabsorption. But because of the thinning of the separation between blood supply and CSF-- potential route for infection!
78
Are any nerves purely motor? Which nerves are purely sensory?
No nerves are purely motor. They always carry proprioceptive sensory fibre afferents (muscle proprioception). However there are purely sensory nerves (I, II, VIII)
79
What is unique about CN I, II, and VIII?
They have meningeal coverings that extend into the periphery. Technically, they are not nerves but are evaginations of teh brain and are potential routes for the transport of bacteria, etc. into the CSN; the optic and olfactory nerves are considered to be tracts of the CNS.
80
What does the position of where the nerve joins the brain tell you?
The position of where the nerve joins the brain is related to the position of the cranial nerve nucleus within the brain.
Most fibres join ventrally or ventrolaterally except the trochlear nerve.
81
What can occur with CN V, VII, and VIII? Why?
They all attach together so they may be involved in one lesion.
82
What nerves would be affected by otitis interna? Why?
CN VII and VIII because they exit together through the internal acoustic meatus.
83
What is the innervation of the pharynx?
Sensory- IX
musculature- IX and X
84
What is the innervation of the larynx?
Sensory- X and XI
Musculature- X and XI
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Transduction
The free nerve endings, nociceptors, of primary afferent neurones respond to noxious stimuli (tissue damage and inflamation)
87
What are the parts of a nociceptive pathway?
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What are the three stages of nociceptive pathways?
89
Under general anaesthesia, what stage is blocked?
90
Describe the 1st stage of nociceptive pathways
\* Stimuli: mechanical, thermal, chemical
\* Nerve fibres: myelinated A fibers and unmyelinated C fibers
\* Nociceptors: Mechanical, thermal, polymodal, silent
\* Silent C fibers-- only start working with an inflammatory process- the threshold will change- start decreasing (become more and more sensitive)-- very painful when turned on!
\* Transduction- stimulus into electric pulse. Lots of transduction channels. Transient Receptor Potential Ion Channel (TRP), Acid- sensing ion channel (ASIC), Serotonin receptors
\* Transduction- Sodium channels (1.1-1.9) and Calcium channels- many different kinds
\* Afferent neurons are bipolar: The body is in the dorsal root ganglia (DRG), one end is free ending in the periphery, the other finishes in the dorsal horn, corelease of aminoacids (glutamate, asparate), neuropeptides (substance P, neurokinin, CGRP)
91
2nd Stage of nociceptive pathways
\* Spinothalamic tract (STT)- major ascending pathway
\* Crosses midline and communicates with different nuclei in the thalamus (then to the cortices)
\* glutamate (neurotransmitter in the thalamus)
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3rd Stage of nociceptive pathways
\*Thalamic nuclei
\* 3rd order neurons
\* Different area of the cortex- sensory-discriminative aspects of pain, motivational-affective aspects of pain, sensory and motor integration
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Third order neurons
Carries sensory information from the thalamus to the cerebral cortex
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Second order neuron
Carries information from the central nervous system to the thalamus. Information traveling along second order neurons deccussates from one side of the CNS to the other side of the CNS
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First order neurons
Conduct impulses from receptors of the skin and from proprioceptors (receptors located in a joint, muscle, or tendon) to the spinal cord or brain stem, where they synapse with second-order neurons. First order neuron's cell bodies reside in ganglion
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Main tracts (part of the 2nd stage of nociception)
\* Spinohypothalamic (SHT), Spinoreticular (SRT), Spinomesencephalic (SMT)
\* SRT reaches the reticular formation (emotional reactions)
\* SHT associated with neuroendocrine and autonomic changes associated with the stress response
\* SMT project to the PAG
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Modulation in the dorsal horn
Grey matter- cell bodies. White matter- myelin.
C fibers are the inhibitors!!
When we are pain there is a fight between the three guys in this picture....
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The Gate Theory of Pain
Non-painful input closes the "gates" to painful input, which prevents pain sensation from traveling to the CNS. Therefore, stimulation by non-noxious input is able to suppress pain.
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What is the antinociceptive pathway?
100
What pathways are involved in the antinociceptive pathways?
101
What are some neurotransmitters in the antinociceptive pathways (dorsal horn)?
102
What areas are connected to the dorsal horn that are impacted by analgesia?
103
Name the input to the dorsal horn from different parts of the body
104
What are some neurotransmitters involved in nociceptive modulation?
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Peripheral sensitisation
Reduction in threshold and an increase in responsiveness of the peripheral ends of nociceptors, the high-threshold peripheral sensory neurons that transfer input from peripheral targets through peripheral nerves to the CNS.
Goes from physiological pain to pathological pain.
Direct consequence of tissue trauma and inflammation
HYPERsensitisation
\* Can happen if you don't give enough anaesthetic in surgery
e.g. male children circumsized- no analgesia- increased pain sensation later in life
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Central sensitization
An increase in the excitability of neurons within the CNS, so that normal inputs begin to produce abnormal responses.
Constant activation of peripheral receptor
Glutamate and asparate activate NMDA receptors- when they are activated they tend to stay activated- do not deactivate on their own frequently
\*\* NMDA receptors are a common target when treating chronic pain (intensive surgeries). Ketamine is the best NMDA med in the world.
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Allodynia
More sensitive to normal stimulation
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Acute pain vs. chronic pain
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Malformations of all kinds
Cyclopic, Arthrogropotic
Reflect early and dramatic problems during CNS development- some are inherited while others reflect in utero or early post-natal exposure to teratogens (e.g. viruses, toxins, drugs, nutrient deficiencies or excesses)
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Some species need post- natal development. Important point is exposure post- natally to teratogens can impact these species more.
(has to do with development of cerebellum)
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Cerebellar hypoplasia causes a number of syndromes (one Walker-Warburg in humans similar to muscular dystrophy, for example)
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Type of malformation. Nodules visible are cells that were supposed to divide and migrate. Clinical signs vary depending on where this occurs.
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\* Defect- lamb's brain- something got in that was lytic late in foetal life. In utero intense necrosis and effective phagocytic response. May not be able to mount a complete inflamm. or immune response, but macrophages are developed and working.
\* second picture excessive tissue
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BVDV- early in pregnancy because no immune response mounted
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BVDV late in pregnancy and therefore immune response mounted
Undersized thymus- accelerated involution and lymphoid death
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Dysraphic syndrome- problem is zipping up neural tube.
Something has gone wrong with neuralation.
Supplemented with folate or folic acid which helps prevent dysraphic syndromes. Viruses can do this as well. Any disruption in neuralation.
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Neurulation
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Neuralation
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Anencephaly- complete absence of a brain
Acrania- absence of head
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Dysraphic sydnrome: agenesis of the prosencephalon- failuare of neural tube closure rostrally (absence of forebrain- prosencephalon)
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Cranium bifidum- meningocoele and meningoencephalocoele
\* rostral neural tube closes and hence formation of at least the leptomeninges but fails to separate from the surface ectoderm--\> focal failure of induction of dorsal skull bones and overlying musculature +/- dura mater
\* cranium bifidum is characterised by usually a dorsal midline defect in the skull through which protrude fluid-filled meninges (meningocoele) or brain within meninges (meningoencephalocoele)
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Lined by meninges, covered by skin, no protrustion of skin
\* called meningocoele (because lined by meninges and just fluid in there- no brain)
\* missing dorsal skull bone and muscles there... so focal failure of overlying mesodermal differential
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meningocoele (just fluid)
and/or meningoencephalocoele (brain withing meninges and fluid)
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Spina bifida- myeloschisis (focal or diffuse failure of closure of the spinal part of the neural tube--\> absence of the spinal cord, meninges, dorsal vertebral arches, overlying muscle and skin along the affected segments)
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meningocoele vs. meningomyelocoele
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spina bifida- meningocoele or meningomyelocoele
and arthrogryposis
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May develop space occupying masses due to congenital defects characteristic of Rhodesian Ridgebacks- stratified squamous and keratinized tube that connects the original ectoderm with deeper structures (often supraspinous ligaments)-- sometimes tube connects down to dorsal dura... Gradally accumulates keratin in the space
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Myelodysplasia- Hydromyelia (distension of the central canal) can develop later but more often developmental defect
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When not lined by ependyma and is it the original central spinal canal... Syringomyelia (fluid filled pocket that is not the central canal, not lined by ependyma)
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When not lined by ependyma and is it the original central spinal canal... Syringomyelia (fluid filled pocket that is not the central canal, not lined by ependyma)
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When not lined by ependyma and is it the original central spinal canal... Syringomyelia (fluid filled pocket that is not the central canal, not lined by ependyma)
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What is the connection with the spinal and vertebral abnormalities and the arthrogryposis?
Any animal with serious spinal cord abnormalities often have arthrogryposis. Nervous system issues. With arthrogryposis- muscles are too short for the growing bones because something has gone wrong with the innervation of those muscles.
Causes: Viruses like BVDV at strategic periods of gestation, inherited problems, toxins, manganese deficiency (lack of growth cartilage development)
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Holoprosencephaly= a spectrum of forebrain (prosencephalon) malformations which typically include agenesis or severe hypoplasia of the olfactory bulbs and tracts
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Skunk cabbage is one cause of cyclopia- from severe malformation of the forebrain, absence of several cranial bones (e.g. ethmoids, lacrimal bones, premaxillae, and nasal septum) presence of a tube-like proboscis located above the midline eye and not communicating with the pharynx and displacement or absence of the pituitary gland--\> prolonged gestation and foetal gigantism
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cebocephaly- eyes too close together- less severe expression of holoprosencephaly (cleft lip, cleft palate are other variations)
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What is considered the leptomeninges and the pachymeninx?
Leptomeninges- arachnoid mater and pia mater
pachymeninx- dura matter
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What is the venous drainage of the spinal cord?
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What is the arterial supply of the spinal cord?
3 longitudinally oriented arteries (2 dorsolateral arteries supply the dorsal grey matter and white matter AND ventral spinal artery- major supply to later and ventral grey matter and the ventral white matter-- only consistent spinal artery \*\*\*)
\* at the foramen magnum or C1, it becomes the basilar artery supplying the brain
\*\* Radicular arteries- occur at each intervertebral foramen (supplied from the vertebral, intercostal, lumbar, and sacral arteries-- they follow the spinal roots entering the vertebral canal and split into dorsal and ventral radicular branches-- they mostly supply lateral white matter)
\*\* note: collateral circulation: radicular and dorsolateral arteries are somewhat inconsistent. Therefore while collateral circulation does occur, it is not very efficient and the spinal cord is very susceptible to hypoxia.
139
What arteries supply the brain?
Internal carotid (left and right), basilar (direct continuation of the ventral spinal artery), rete mirabile- name given to any blood vessel that breaks up into a plexus and reforms into a single blood vessel.
\* Circle of Willis- from the basilar and internal carotids
\* From the arterial circle three vessels supply the cerebrum- rostral cerebral artery- lateral to the optic chiasm, supplies rostralmedial half of the cerebral hemispheres, middle cerebral artery- largest vessel- arises just rostral to hypophysis- supplies lateral part of cerebral hemispheres and rostral brain stem, and caudal cerebral artery- arises near the oculomotor nerve, supplies caudomedial part of the cerebral hemispheres)
\* cerebellar blood supply- rostral (from arterial circle) and caudal (from basilar a.) cerebellar artery
\* brain stem supply from basilar artery supply medulla and the pons
\* meningeal arteries: rostral, middle, and caudal meningeal arteries
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What is the venous drainage of the canine brain?
\* dorsal and ventral set which communicate freely
\* paired and unpaired ones
\* run in dural folds or boney canals within the calvarial walls
\* drainage is to the large veins draining the head region
\* maybe a pathway for infection into the brain (e.g. the cavernous sinus)
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Potential routes of blood supply to the arterial circle
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Arterial supply coming off the circle of willis
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What is the telencephalic septum/ septum pellucidum?
Thin membrane which lies like a window between the rostral aspect of the 2 lateral ventricles. Arises from the dorsal aspect of the hippocampal fornix and stretches dorsally to the corpus callosum.
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Relationship between the third ventricles and lateral ventricles
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What is the interventricular foramina?
Connect each lateral ventricle to the cenrally located third ventricle
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Hippocampal fornix
Part of the limbic system- brain structures involved in emotional behaviour
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What is the third ventricle associated with? What forms the hole of its donut shape?
What are the three recesses associated with the third ventricle?
Diencephalon. Interthalamic adhesion forms the "hole" of its donut shape.
1. optic recess
2. infundibular recess
3. suprapineal recess
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What is the mesencephalic aqueduct?
aka aqueduct of Sylvius is part of the neural tube which lies in the mesencephalon and connects the third and fourth ventricles- widens caudally. Common site of hydrocephalus (congenital or acquired- a build up of CSF)
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What is the fourth ventricle associated with?
Two brain divisions: metencephalon and myelencephalon
\* ventral to cerebellum and dorsal to the brain stem parenchyma
\* Lateral apertures (foramen of Luschke) which are openings between the fourth ventricle and the subarachnoid space at the level of the CNVIII
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What is the central/spinal canal?
The caudal continuation of the fourth ventricle- the first part of the central canal lies within the myelencephalon
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What is the subarachnoid space?
Lies between the pia and arachnoid and is filled with CSF
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What is a CSF cistern? What are the two clinically important ones?
Formed by the arachnoid mater shortcutting across between brain tissues to form an enlarged space between it and the pia.
1. Cerebelomedullary cistern- lies in the angle between the caudal cerebeelum and the medulla oblongata
2. Lumbar cistern which lies at the caudal end of the spinal cord, and may be approached by inserting a needle between L7 and the sacrum in the dog.
\*\* used to sample CSF and to insert radio-opaque dye into the subarachnoid space to outline the shape of the spinal cord for radiography to look for spinal cord swelling or compression
3. intercrural cistern- the third cistern and lies between the crus cerebri, caudal to the hypophysis and rostral to the pons
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Radio opaque
Substances appear white (inability of electromagnetic radiation to pass through a material). Bottle cap in the picture
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What is CSF? Composition too.
A clear straw coloured fluid which surrounds the neuraxis (the axis of the CNS- denotes the direction in which the CNS lies)
Composition:
\* potassium, calcium, chloride, sodium, magnesium, glucose, protein (albumin), cells (mainly acellular but some WBCs)
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What are arachnoid villi?
Arachnoid granulations or arachnoid villi are small protrusions of the arachnoid (the thin second layer covering the brain) through the dura mater
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What are choroid plexi? Where are they?
Tangled networks of blood vessels, pia, and ependyma protruding into the ventricles.
\* in the fourth ventricle originating from the roof and protruding into the lateral apertures
\* in the dorsal aspect of the third ventricle
\* in the dorsomedial aspect of the lateral ventricles
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Where is CSF produced? How does it flow?
1) choroid plexi- primary site of production- by ultrafiltration of blood plasma and by active transport
2) brain parenchyma, and ependymal cells- small amount
Production rate: dog 0.05 ml/min, cat 0.017 ml/min, humans: complete turnover 3 to 4 times/day
\*\* it is produced in all ventricles and flows caudally towards the brain's ventricular system, out of the lateral apertures into the subarachnoid space, over the cerebral hemispheres and caudally along the spinal cord. A small amount also flows from the fourth ventricle along the central canal to the terminal end of the spinal cord.
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What is CSF absorped?
By the arachnoid villi, small evaginations of arachnoid mater and dura along with subarachnoid space that protrude into the large venous sinuses surrounding the CNS
\* acts like a one way ball valve so that if the CSF pressure is greater than venous pressuer, than the valve opens and CSF flows into the vein
\* If venous pressure is greater than CSF pressure, then the villi collapse and less absorption occurs
\*\* Other sites of absorption include: lymphatics around the origins of teh cranial and spinal nerves. Veins around the brain and within the meninges.
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What are the three functions of CSF?
1) physical protection- physical cushion, buffer against pressure changes within the CNS
2) chemical protection- more stable chemically than blood plasma, allows increased regulation of the neuronal environment, CSF pH directly influences the function of the medullary respiratory centre
3) nourishment- may transport nutrients between blood and the brain, may transport neuroendocrine substances and neurotransmitters
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Why is an adult nervous system proportionally smaller than that in a foetus or neonate?
Neurons that do not connect into neural pathways degenerate. Large heads are a sign of immaturity.
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General overview of NS development
Development commences day 17 in the dog and 18 in the horse (mean gestation length 63 and 340 respectively).
Originates as a flat plane of tisse which rolls up and forms a tube by "zipping" up from the mid section, in rostral and caudal directions. The cranial end forms the brain by enlarging and folding and divides laterally into the 2 hemispheres. A dorsal outgrowth of the hindbrain forms the cerebellum. The caudal majority of the neural tube remains as an elongated tube forming the spinal cord. The PNS is formed by the outgrowth of axons and dendrites from the developing brain and spinal cord.
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What is the notochord?
Primitive axial skeleton (skull and jointed vertebrae) in higher vertebrates. It is only a transient support in mammalian develoopment and persists in the nucleus pulposus of the intervertebral disc. It is required for the development of the neural tube.
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What are the layers of the neurectoderm?
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What does each layer of the neuroectoderm turn into functionally in terms of neurons?
\* germinal layer- initially proliferative becomes ependyma (squamous to columnar) when proliferative function exhausted
\* mantle layer- primitive neurons and spongioblasts which form grey matter of the CNS. It is the middle layer except where it becomes external in the cerebral hemispheres.
\* Marginal layer- primarily axons of the mantle layer which form the white matter. It is the outer layer except in the cerebral cortex.
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What cells does the neuroectoderm give rise to?
\* Neuroblasts- immature neurons which do NOT divide again (despite "blast")
\* spongioblasts- glial cell progenitors
\* astrocytes, oligodendroglia, and ependyma
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What is the sulcus limitans?
\* A longitudinal groove that develops in the lateral wall of the neural tube extending from the midbrain to the caudal spinal cord. It marks the separation between the alar (primarily sensory) and basal (primarily motor) plates
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What is a sclerotome?
Each complete vertebrae is a product of the fusion of four sclerotomes. Vertebral anomalies aries due to abnormal segmentation of somites or formation of sclerotomes.
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What does the notochord remnant become?
Nucleus pulposus of the intervertebral disc.
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What are the two plates that make up the spinal cord?
Alar plate and basal plate (alar plate forms the dorsal median septum from its two halves, and the basal plate forms the ventral median fissure from its two halves)...
Also dorsal grey column are formed by alar plate neuroblasts. While ventral grey columns and intermediate grey columns are formed from basal plate neuroblasts.
dorsal column- sensory
intermediate column- visceral motor
ventral column- somatic motor
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What are dorsal roots?
Afferents (dendrites) of spinal ganglion neurons which grow into the cord
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What are ventral roots?
Axons of ventral grey column neurons which grow out of the cord
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What are spinal nerves?
Formed by joining of dorsal and ventral roots lateral to the spinal ganglion. They enter and exit via intervertebral foramina
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What are the cervical and lumbosacral intumescences?
Enlarged regions of the spinal cord which occur because of the large amount of tissue requiring innnervation within the limbs.
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What forms the folia of the cerebellum?
What are the cerebellar peduncles and how are they formed?
Folia formed via the continued division of the neurons so they tend to fold up on each other.
Cerebellar peduncles are formed from developing nerve processes which connect the cerebellum to the rhombencephalon.
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What two cellular migrations occur during development?
1) differentiating mantle cells (no longer dividing) form
a) Purkinje cells early in embryonic life so they are susceptible to teratogens
b) neurons of the cerebellar nuclei
b) Dividing germinal cells migrate to the surface of the cerebellum to form the external germinal layer. This gives rise to the:
a) granule cell layer
b) stellate cells of the molecular layer
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What does the degree of motor function and coordination correspond to in early newborn animals?
The degree of cerebellar development
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What forms the tectum? What forms the tegmentum?
Tectum formed by the alar plate. Tegmentum formed by the basal plate.
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What is the hypophysis?
The pituitary gland. The smallest but most important endocrine gland. Anterior and Posterior Pituitary Gland.
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What is the optic cup?
aka retina are the neuronal cell bodies of the light sensitive cells.
The optic nerve and optic tract are formed by the caudally growing cell processes of retinal cell neurons growing towards the diencephalon.
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What is this showing the development of?
Pituitary gland aka hypophysis
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What is the crus cerebri?
Anterior portion of the cerebral peduncle which contains motor tracts.
## Footnote
\*\* the corticospinal tract constitutes a large part of the internal capsule, carrying motor information from the primary motor cortex to the lower motor neurons in the spinal cord. Above the basal ganglia the corticospinal tract is part of the corona radiata. Below the basal ganglia the tract is called the crus cerebri (a part of the cerebral peduncle) and below the pons it is referred to as the corticospinal tract
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What is the internal capsule?
A white matter structure in each cerebral hemisphere that carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the global pallidus. \*\* the internal capsule contains both ascending and descending axons. Contains fibers going to and coming from the cerebral cortex.
\*\* the corticospinal tract constitutes a large part of the internal capsule, carrying motor information from the primary motor cortex to the lower motor neurons in the spinal cord. Above the basal ganglia the corticospinal tract is part of the corona radiata. Below the basal ganglia the tract is called the crus cerebri (a part of the cerebral peduncle) and below the pons it is referred to as the corticospinal tract
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What are the telencephalic vesicles?
A pair of huge outgrowths of prosencephalon that extend dorsally and laterally to form the cerebral hemispheres. Initially large fluid-filled structures, mostly occupied by the lateral ventricles. However, as the neural tissue continues to proliferate, the lateral ventricles are reduced in size and the hemispheres are mostly tissue rather than fluid by birth.
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What forms the leptomeninges?
The arachnoid and pia mater surrounding the entire CNS are formed from the neural crest and adjacent mesodermal cells.
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What nerves do you block to get anaesthesia and flaccid paralysis of muscles? Explain what happens if you only block one or the other.
Block both sensory (CN5 aka trigeminal n.) and motor (CN7 aka facial n.) in different places to get anaesthesia and flaccid paralysis of muscles.
\* If you only block CN7 animal can still feel
\* If you only block CN5 then will still get local muscle reflexes and purposeful movements (except for masticatory mm.)
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What is the name, function, exit from skull, and brain exit of CN I? Signs of dysfunction? Location of nerve cell bodies?
Olfactory
Function: olfaction
Exit from the skull: cribiform plate
Brain exit: Telencephalon
Sign of dysfunction: lack of smell
Location of nerve cell bodies: nasal mucosa and the meninges extend through cribiform plate of ethmoid bone
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What is the name, function, exit from skull, and brain exit of CN II? Signs of dysfunction? Location of nerve cell bodies?
Optic
Function: vision
Exit from skull: Optic foramen
Brain exit: Diencephalon
Signs of dysfunction: Visual and PLR deficits (pupillary light reflex)
Nerve cell bodies: in the retina (meninges extend to the sclera of the eye)
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What is the name, function, exit from skull, and brain exit of CN III? Signs of dysfunction? Location of nerve cell bodies?
Oculomotor
Function: PLR, ocular movement (ventral, medial, dorsal recti, ventral oblique, levator palpebrae)
Exit from skull: Orbital fissure in small animals, orbitorotundum in ruminants
Brain exit: Mesencephalon
Dysfunction: PLR deficits (pupillary light reflex), strabismus (lateral and ventral deviation of the eyeball)
Location of nerve cell bodies: ciliary ganglia for PS fibres are located just behind the eye (nerves run through the wall of the cavernous sinus before exiting the orbital fissure)
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What is the name, function, exit from skull, and brain exit of CN IV? Signs of dysfunction? Location of nerve cell bodies?
Trochlear
Function: Ocular movement (dorsal oblique)
Exit from skull: Orbital fissure in small animals, orbitorotundum in ruminants (like III)
Brain exit: Mesencephalon
Dysfunction: Strabismus (lateral rotation of the dorsal aspect of the eye)
Location of nerve cell bodies: Nerves enter or exit ventrally, except CN IV which exits dorsally, decussates immediately at the level of the caudal colliculus and then courses ventrally around the brainstem.
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What is the name, function, exit from skull, and brain exit of CN V? Signs of dysfunction? Location of nerve cell bodies?
Trigeminal
Function: Sensory to skin of face, mucous membranes of head, motor to muscles of mastication
Exit skull- Opthalmic- orbital fissure, maxillary- round foramen, mandibular- oval foramen
Exit brain: metencephalon
Dysfunction: Masticatory muscle paralysis (drooped jaw), facial sensory deficits
Location of nerve cell bodies: Trigeminal ganglion is located in the petrous temporal bone inside the cranial vault, three branches divide before the nerve leaves the skull (mandibular, maxillary, and opthalmic)
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What is the name, function, exit from skull, and brain exit of CN VI? Signs of dysfunction?
Abducens
Function: Ocular movement (retractor bulbi, lateral rectus)
Exit skull: (same as III) orbital fissure in small animals, orbitorotundum in ruminants
Exit brain: Myelencephalon
Dysfunction: Strabismus (medial) and failure of globe retraction
Extra info: Exits the medulla oblongata ventrally just caudal to the pons
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What is the name, function, exit from skull, and brain exit of CN VII? Signs of dysfunction? Location of nerve cell bodies?
Facial
Function: Taste on rostral 2/3 of tongue, motor muscles of facial expression, PS to mandibular, sublingual, palatine, nasal, lacrimal glands
Exit skull: Internal acoustic meatus, facial canal, then exits through the stylomastoid foramen
Exit brain: Myelencephalon
Dysfunction: Paralysis of facial muscles (drooping of the ear, lip, eyelid), decreased lacrimation, decreased taste sensation
Ganglion: Geniculate ganglion in external genu of the facial canal in the petrous temporal bone AND pterygopalatine ganglion, ventral to eye on top of the pterygoid muscle and fibres go to the sublingual and mandibular salivary glands
Extra info: Travels in close proximity with the CN VIII through the internal acoustic meatus but leaves CN VIII to enter the facial canal in the petrous temporal bone close to the middle ear chamber. Susceptible in middle ear disease.
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What is the name, function, exit from skull, and brain exit of CN VIII? Signs of dysfunction? Location of nerve cell bodies?
Vestibulocochlear
Function: Vestibular- balance, Cochlear- hearing
Exit skull: stays within the skull. Goes into the petrous tempoeral bone through the internal acoustic meatus
Exit brain: myelencephalon
Nerve cell bodies located in ganglia (vestibular and spiRal) within the petrosal bone of inner ear (aka petrous temporal)
Extra info: also susceptible to middle ear disease because it enters the facial canal in the petrous temporal bone
Dysfunction: balance problems (head tilt, body twisting, ataxia, rolling, nystagmus (involuntary eye movement)), hearing deficits
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What is the name, function, exit from skull, and brain exit of CN IX? Signs of dysfunction? Location of nerve cell bodies?
Glossopharyngeal
Function: Taste on the caudal 1/3 of tongue, sensory to pharynx, carotid sinus, motor to stylopharyngeus m., PS to parotid and zygomatic salivary glands
Exit skull: jugular foramen within the tympano-occipital fissure
Exit brain: Myelencephalon
Dysfunction: dysphagia (difficulty in swallowing), respiratory noise (laryngeal paralysis)
Ganglia: Proximal (petrosal) ganglion in the jugular foramen, otic ganglion is located near the auditory tube and postsynaptic fibres are distributed to the parotid and zygomatic salivary glands
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What is the name, function, exit from skull, and brain exit of CN X? Signs of dysfunction? Location of nerve cell bodies?
Vagus
Function: Sensory to pharynx, larynx, and viscera, sensory to external ear canal, taste on root of tongue and epiglottis, PS to viscera
Exit skull: jugular foramen within the tympano-occipital fissure
Exit brain: myelencephalon
Dysfunction: dysphagia (difficulty in swallowing), respiratory noise (laryngeal paralysis)
Ganglion: proximal (jugular) ganglion- sensory only in the jugular foramen, distal (nodose) ganglion- sensory only located at the level of the tympanic bulla (after this, the vagus joins the sympathetic nerves to form the vagosympathetic trunk), the cranial laryngeal nerve arises from the vagus at the level of the distal ganglion and innervates the cricothyroideus m.
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What is the name, function, exit from skull, and brain exit of CN I? Signs of dysfunction? Location of nerve cell bodies?
Accessory
Function: Motor to trapezius and brachiocephalicus mm.
Exit skull: jugular foramen within the tympano-occipital fissure. External branch enters skull through foramen magnum.
Exit brain: myelencephalon
Dysfunction: Atrophy, dysfunction of trapezius, respiratory noise (laryngeal paralysis)
Arises from neurons located in two places- the medulla and the lateral portion of the ventral grey column from spinal cord segments C1 to C7. It innervates portions of the cleidocervicalis, sternocephalicus, and the brachiocephalicus.
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What is the name, function, exit from skull, and brain exit of CN XII? Signs of dysfunction? Location of nerve cell bodies?
Hypoglossal
Function: motor to tongue muscles
Exit skull: hypoglossal canal
Exit brain: myelencephalon
Dysfunction: paralysis and deviation of the tongue if unilateral lesion
Arises as a series of rootlets from the ventrolateral sulcus of the medulla. Supplies extrinsic tongue muscles: styloglossus, hyoglossus, genioglossus, geniohyoideus AND intrinsic tongue muscles.
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What bone is the foramen magnum part of? What comes out?
Occipital bone
Contents: spinal cord, basilar artery, venous plexus, spinal part of CNXI (accessory n.)
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What bone is the hypoglossal canal part of? What comes out?
Occipital bone
CNXII (hypoglossal n.)
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What bone is the stylomastoid foramen part of? What comes out?
Temporal bone
CNVII (Facial n.)
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What bone is the tympano-occipital fissure part of? What comes out?
Temporal and Basioccipital bones
CNIX (Glossopharyngeal n.), CNX (vagus n.), CN XI (accessory n.), sympathetic nerves, small veins, internal carotid artery
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What bone is the external acoustic meatus part of? What comes out?
Temporal bone
Contents: External ear canal
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What bone is the oval foramen part of? What comes out?
Sphenoid bone
CNV (trigeminal n.) mandibular branch
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What bone is the round foramen (cat) part of? What comes out?
Sphenoid bone
CNV maxillary branch (trigeminal n.)
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What bone is the alar canal (in dogs- name two parts) part of? What comes out?
Sphenoid bone
Rostral alar foramen: maxillary artery and vein
Caudal alar foramen: maxillary artery and vein and CNV maxillary branch
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What bone is the orbital fissure part of? What comes out?
Sphenoid bone
Contents: CN III (Oculomotor n.), CN IV (trochlear n.), CN V ophthalmic branch, CN VI (Abducens n.)
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What bone is the optic canal part of? What comes out?
Sphenoid bone
CN II (optic n.)
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What bone is the cribiform plate part of? What comes out?
Ethmoid bone
CN I (olfactory)
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What is unique about CN I and CN VIII (Vestibulocochlear)?
they remain intracranial
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What bone is the infra-orbital canal (name the two) part of? What comes out?
Maxilla bone
Maxillary foramen & infraorbital foramen: Maxillary artery, vein, and nerve which continue as the infraorbital artery, vein, and nerve
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What bone is the jugular foramen part of? What comes out?
Temporal and Occipital bones
Contents: CN IX (Glossopharyngeal), CN X (vagus), CNXI (accessory), sigmoid sinus
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What bone is the internal acoustic meatus part of? What comes out?
Temporal Bone
CN VII (facial), CN VIII (vestibulocochlear)
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What bone is the round foramen part of? What comes out?
Sphenoid bone
CNV (trigeminal) maxillary branch (DOG)
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What bone is the trigeminal canal part of? What comes out?
Temporal bone
CNV and trigeminal ganglion
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What bone is the mandibular canal (name two holes) part of? What comes out?
Mandible
Two holes: Mandibular foramen and mental foramen
CNV mandibular branch continuing as the inferior alveolar nerve and running with the inferior alveolar artery and vein
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What nerves innervate the extraocular muscles?
\* CNIII (oculomotor), CN VI (Abducens), CN IV (Trochlear)
Movement of the eyeball is achieved through contractio and relaxation of six extraocular muscles in the dog: dorsal rectus m, ventral rectus m., medial rectus m., lateral rectus m., dorsal oblique m., ventral oblique m.
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What nerves are associated with the pharynx and larynx?
CN IX (Glossopharyngeal), CN X (vagus), and CN XI (accessory)
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What three nerves come off the brain stem together and may be involved in one lesion because of their proximity to each other?
CN V, VII, and VIII
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What nerves carry the following sensory information into the CNS?
a) vision
b) balance and hearing
c) olfaction
a) CN II- optic
b) CN VIII- vestibulocochlear
c) CN I- olfactory
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a) What branches of the trigeminal nerve supplies motor innervation to the muscles of mastication?
b) What branches of the trigeminal nerve supply facial sensation?
a) Mandibular branch
b) Ophthalmic branch and Maxillary branch
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What is the main function of CN VII?
General somatic efferent fibre- ear canal
General visceral efferent fibre- PS control to some salivary glands, lacrimal glands, nasal cavity, and palate
Special visceral afferent fibre- taste to the rostral 2/3 of the tongue
General somatic efferent fibre- motor function to the muscles of facial expression
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What cranial nerve supplies the muscles of the tongue?
CN XII- Hypoglossal n.
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What does the spinal accessory nerve supply?
Motor to trapezius and brachiocephalicus muscles
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Which nerve provides the efferent arm of the pupillary light reflex?
CN III- Oculomotor n.
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Which three cranial nerves are purely sensory?
CN I, II, and VIII (vestibulocochlear)
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What is the autonomic nervous system?
An involuntary system that is concerned with the internal environment of the body. Unlike the somatic, where a nerve connects direclty between neurons within the CNS and the effector organs, in the ANS there is a sequence of two neurons which connect the CNS with target organs. The nerves from the presynaptic neuron in the CNS extend to the periphery where they synapse with a post synaptic neuron within one of the autonomic ganglia.
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The nerves from the presynaptic neurons extend into the periphery as parts of what 3? What do the postsynaptic fibres from the neurons in the various ganglia innervate?
1) Parts of the cranial nerves (parasympathetic)
2) Sympathetic chain
3) Pelvic nerves (parasympathetic)
\* Postsynaptic fibres from the neurons in the various ganglia innervate cardiac muscle, smooth muscle, and glands.
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What is the craniosacral component of the ANS?
\* Craniosacral component: The parasympathetic rest and digest part with acetylcholine as its neurotransmitter throughout
\* Thoracolumbar part: sympathetic fight and flight part which has noradrenaline as its transmitter for the postganglionic nerve endings in the effector organs
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What controls the activity of the presynaptic neurons in the CNS parasympathetic brain nuclei or the intermediate horn of the spinal cord?
UMN's in the hypothalamus
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What is the hypothalamus?
Small area in the ventral diencephalon of the forebrain, in the floor of the third ventricle, and is a functional link between the nervous and endocrine systems. Controls the endocrine glands. Vital in regulation of homeostasis including thermoregulation.
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Where is the origin of the sympathetic/ thoracolumbar division?
\* Lateral intermediate horn of spinal cord segments C8 to L3/L4
\* efferent fibres leave the spinal cord in the ventral root to the proper spinal nerve
\* Ramus communicans- leaves the proper spinal nerve and conveys autonomic fibres in both directions between the spinal nerve and the sympathetic trunk
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What is the sympathetic trunk?
\* Bilateral paired strand of sympathetic and visceral afferent fibres
\* runs in a craniocaudal direction just ventrolateral to the vertebral column from C8 to L4/L5, occasionally as far caudal as L7
\* Sympathetic trunk (paravertebral) ganglia- a ganglion occurs where each ramus communicans connects to the sympathetic trunk, fibres may pass through several ganglia before synapsing
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What are the splanchnic nerves?
\* sympathetic supply to the abdomen
\* Originates from sympathetic fibres which leave the sympathetic trunk in the caudal thoracic and cranial lumbar area
\* prevertebral ganglia: Splanchnic nerves synapse in a ganglion within the body cavity when they are going to deeply located viscera e.g. coeliac, cranial mesenteric, and caudal mesenteric ganglia
\* postsynaptic fibres: travel with blood vessels to terminate in the abdominal organs
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What are the fibres from C8 to T7 called that ascend to supply sympathetic innervation to the head?
Cervicosympathetic trunk
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What is the vagosympathetic trunk?
The combined cervicosympathetic trunk ascending to the head region and the vagal (parasympathetic) fibres descending to the body
\* located in the carotid sheath of the neck
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What is the cervicothoracic ganglia (stellate)? What is the ansa subclavia?
Largest autonomic ganglion in the dog. It is formed by fused caudal cervical and cranial thoracic paravertebral ganglia. Ansa subclavia- the ventral continuation of sympathetic innervation from the cervicothoracic ganglion splits to pass around the subclavian artery at the thoracic inlet.
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What is the middle cervical ganglion?
Located where the ansa subclavia joins the vagosympathetic trunk at the thoracic inlet. Fibres entering the cervicothoracic or middle cervical ganglion may synapse or pass through without synapsing. The latter fibres synapse in the cranial cervical ganglion.
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What is the cranial cervical ganglion?
Located deep to the tympanic bulla. Fibres exiting this ganglion travel in association with arteries to supply the head.
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What path do sympathetic fibres traveling to the head take?
\* Originate from C8 to T7 spinal cord segments--\> travel through the cervicothoracic ganglion--\> into the ansa subclavian--\>through the middle cervical ganglion--\> leave the thorax and enter the vagosympathetic trunk to ascend towards the head--\> enter the cranial cervical ganglion near the ear where most fibres synapse--\> and then travel into the head in association with the arteries
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What is the basis of the sympathetic innervation of the abdominal and pelvic organs?
Fibres from the sympathetic trunk form splanchnic nerves and ramify to form a plexus around the root of the mesenteries and the abdominal aorta. A number of ganglia are scattered. Distal to the caudal mesenteric ganglion the postganglionic fibres from the hypogastric nerves that course caudally towards the pelvis either side within the mesorectum.
\* the pelvic plexus is the network of autonomic fibres formed by the pelvic nerves (PS) and hypogastric nerves (sympathetic) that ramify around the walls of the urinary bladder and rectum. It lies mainly within the mid to ventral part of the pelvic cavity either side of the rectum and bladder.
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Where does the parasympathetic supply to the head arise from?
Parasympathetic nuclei of the cranial nerves III, VII, IX
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Where is the PS nucleus of CN III? What about CN VII and IX?
\* PS nucleus of III- mesencephalon - PS supply of the iris and ciliary body
\* PS supply of salivary glands via CN VII and IX-- nuclei located in the myelencephalon
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Where does the vagus separate from the sympathetic trunk? then what happens?
At the middle cervical ganglion (then after traversing the thorax and splitting and reforming into the dorsal and ventral branches through the diaphragm to the abdominal viscera.
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What is interesting about the functioning of the enteric nervous system?
it has intrinsic activity so can function in isolation from the CNS but is also responsive to the CNS
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What is the primary controller of gut secretion? What is the primary controller of gut motility?
Gut secretion- submucosal plexus
gut motility- myenteric plexus
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Where does PS innervation arise from in the caudal end of the body?
S1 to S3- sacral spinal cord and exits in the ventral root-- continues as the pelvic nerves on the lateral wall of the distal rectum which joins the pelvic plexus and supplies the pelvic viscera and genitalia
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What sort of tissue does the ANS innervate?
smooth muscle, cardiac, and glands
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What is the anatomical division of the ANS? Functional?
Anatomic division- craniosacral (PS)
thoracolumbar (symp)
Functional: symp and PS
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Where are the presynaptic nerve cell bodies located in the neuraxis for the symp and PS?
symp: caudal hypothalamus, brain stem, lateral horn TL spinal cord
PS: rostral hypothalamus, brain stem, sacral spinal cord
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Anatamoy of the innervation of the urinary bladder
Arises from the sacral spinal cord and exits the ventral root and continues as the pelciv nerves which joins the pelvic plexus
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How does the eye receive:
a) sympathetic innervation
b) PS innervation
c) what is the function of each type of innervation of the eye?
a) via cranial cervical ganglion
b) PS innervation via CN III
c) if symp innervation is dominant- acts upon the radial muscles of the iris causing dilation of the pupil, if PS is dominant it acts upon the circular muscles of the iris causing contraction
