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Nervous System Flashcards

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1
Q

What are somatic afferent pathways?

A

Convey info from receptors on skin and somatic tissue. Excludes special receptors of eye and inner ear.
Concerned with touch, pressure, vibration, temp., pain, and kinesthetic sensations. Primary neuron for this is located in dorsal root ganglia of spinal nerves.
Broken into lemniscal (two large ascending pathways allowing for high degree of spatial descrimination) and extralemniscal systems (characterised by slower propogation and less precise localisation of stimuli).
Special somatic afferent pathways are visual, vestibular, auditory.

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2
Q

What are nerves?

A

Bundles of axons made up of neurons

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3
Q

What are ganglia?

A

Clusters of neuronal cell bodies.

Form visible swellings on peripheral nerves.

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4
Q

What is white matter?

A

Made of axons connecting different parts of grey matter to each other. Nerve fibres or nerve tracts.
White colour is from the presence of myelin - insulates.

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5
Q

What is grey matter?

A

Contains the cell bodies, dendrites and axon terminals of neurons. Synapses occur here.

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6
Q

What is the afferent NS?

A

Sensory, impulses away from peripheral receptors, towards the CNS.

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7
Q

What is the efferent NS?

A

Motor, impulses exit the CNS, towards effectors.

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8
Q

What does somatic mean?

A

skeletal

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9
Q

What does visceral mean?

A

organs

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10
Q

What are somatic motor pathways?

A

Regulated by upper and lower motor neurons.
Lower and located in ventral column of grey matter within spinal cord and within somatic motor nuclei of certain cranial nerves.
Upper motor neurons involved in more complex reflexes and initiate voluntary movements. Located within motor area of neopallium and other regions of brain, including reticular formation and red nucleus. Upper motor neurons exert control via excitation or inhibition of lower motor neurons rather than acting directly on muscle fibres.

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11
Q

What is the pyramidal system?

A

originates from neurons in neopallium, appear as pyramids of medulla oblongata.
Three fibre groups, in dogs, 50% terminate on cervical segments of spinal cord.
Extra pyramidal system - includes all areas of the brain invovled in regulating motor functions that are not inluded in the pyramid system.
Cerebellum controls both of these systems.

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12
Q

The central nervous system consists of?

A

Brain (encephalon) and spinal cord (medulla spinalis).

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13
Q

The peripheral nervous system consists of?

A

Autonomic NS - involuntary reactions
Somatic NS - voluntary reactions, skeletal muscle.
Spinal nerves
Cranial nerves

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14
Q

What is the functional unit of the nervous system? What are its components?

A

Neuron.
Divided into; cell body (perikaryon), dendrites (transmit signals towards perikaryon), axons (conveys impulse away from perikaryon), axon terminal, neuroglial cells (supportive, provide nutrients to neuron).
Can be multipolar (multiple branches), bipolar (two branches), or pseudounipolar (cell body joined to individual branch that then joins another branch, T section).

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15
Q

What are the components of nerves?

A 
Sensory end (sensation receptors), integration centre (brain and spinal cord), and effectors (skeletal muscle and visceral organs).
Nerve cell is polarised.
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16
Q

Discuss the stimulus response apparatus.

A

Five elements arranged in a series; receptor region, afferent neuron, synapse, efferent neuron, effector.
Can be interneurons - one or more additional neurons interposed in the chain between afferent and efferent neurons.
Knee jerk/patella reflex is an example of a primary, elementary, or monosynaptic reflex arc (one afferent and one efferent).

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17
Q

What is neuroglia?

A

Supporting tissue of the brain and spinal cord.

Supports neurons, assists in nutrition and neurotransmission. Prevents leakage of signals.

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18
Q

Draw a diagram giving an overview of organisation of the nervous system.

A

CNS (brain and spinal cord) outputs to the Efferent division of the Peripheral NS. CNS receives inputs from afferent division of the Peripheral NS (cranial, spinal, autonomic nerve trunks and ganglia).
Afferent division has inputs from sensory stimuli and visceral stimuli (both ascending impulses).
Efferent (F off-high to low) division sends impulses to the Somatic Nervous system and the Autonomic NS.
Somatic NS feeds down to motor neurons and then skeletal muscle (effector organs).
ANS feeds down to sympathetic and parasympathetic NS which then affect smooth and cardiac muscle as well as glands (all effector organs as well).

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19
Q

Describe the anatomy of the autonomic nervous system.

A

Broken into parasympathetic (rest and digest) and sympathetic (fright, flight, fight).

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20
Q

Describe an efferent nerves anatomy.

A

Preganglionic neuron runs from CNS into PNS, synapses at the autonomic ganglion with the post ganglionic neuron.
Post ganglionic neuron acts on effector organs (cardiac, smooth muscle, glands, adipose tissue).

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21
Q

What is the somatic nervous system comprised of?

A

One ganglion connecting spinal cord to muscle.

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22
Q

What is different about PNS fibres?

A

They have a long preganglionic fibre (from brain stem or spinal cord) and short postganglionic fibre.
Can also be called Cranio-Sacral NS.

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23
Q

What are some common parasympathetic pathways?

A

Oculomotor (III)
Facial (VII)
Glossopharyngeal (IX)

Para - runs parallel to sympathtic

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24
Q

Describe the anatomy of the sympathetic NS.

A

Pre-ganglionic fibres run from thoracic and lumbar spinal cord.
Ganglia can be arranged in 3 anatomical patterns; sympathetic chain, adrenal medulla, collateral ganglia.
Also called Thoraco-lumbar NS (due to area it originates from).
Connects to visceral organs via middle cervical, cervicothoracic, celiac, celiac mesenteric plexus, caudal mesenteric ganglions, and hypogastric nerve.

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25
What are the important components of the sympathetic nervous system within the thoracic cavity?
Ansa subclavia - branches from cervicothoracic ganglia to the middle cervical ganglia. Middle cervical ganglia - present just cranial to the heart base (pulmonary veins). Cervicothoracic ganglia - present dorsal to the middle cervical ganglia. Vagosympathetic trunk - cranial to the middle cervical ganglia. Thoracic ganglia - caudal to the cervicothoracic ganglia.
26
What are the important components of the sympathetic NS in the abdominal cavity?
``` Splanchnic nerve Celiac ganglia Cranial mesenteric ganglia Caudal mesenteric ganglia Renal ganglia Gonadal ganglia ```
27
What are the different classes of spinal nerves?
``` Cervical Thoracic Lumbar Brachial plexus Lumbo-sacral plexus ```
28
What are the cranial nerves?
``` I - olfacotry - special sensory II - optic - special snesory III - oculomotor - motor IV - trochlear - motor V - trigeminal - mixed VI - abducent - motor VII - facial - mixed VIII - vestibulocochlear - special sensory IX - glossopharyngeal - mixed X - vagus - mixed XI - accessory (spinal) - motor XII - hypoglossal - motor On Occasion Our Trusty Truck Acts Funny, Very Good Vehicle Any How. Some Say Marry Money But My Brother Says Big Brains Matter More (B=both) ```
29
What is the spinal cord?
Cylindrical dorse-ventrally flattened cord. Runs from foramen magnum (opening at base of skull) to sacrum/coccygeal. Divisions are; cervical, thoracic, lumbar, sacral, coccygeal/caudal. Meningis wraps around cord and provides protection. CSF provides nutrients. At bottom there is a lumbar intumescense (swelling) before it divides into the conus medullaris, filum terminale, and cauda equinae.
30
Describe the transverse section of the spinal cord.
Central canal bordered by the central grey matter (H shape). Outer white matter. Dorsal root fibres run from small wings of H. Ventral root fibres run from large wings f H. Ventral median fissure (line down centre) Dorsal horn (small wings of H) Ventral horn (large wings of H) Dorsal funiculus (white matter in between H on dorsal side). Ventral funiculus (white matter between H on ventral side) Lateral funiculus (white matter on both lateral sides) Dorsal root ganglion (are where dorsal and ventral root fibres meet outside of the cord. Spinal ganglia form spinal nerve and exit from intervertebral foramen.
31
What fibres does the dorsal horn contain dorsomedially?
somatic afferent
32
What fibres does the dorsal horn contain dorsolaterally?
visceral afferent
33
What does the grey matter of the spinal cord contain?
Somatic efferent neurons located ventrally, and visceral efferent neurons which form additional lateral horn in thoracolumbar and sacral regions.
34
Which plate do dorsal horns correspond to?
alar plate - somatic afferent and visceral afferent neurons
35
Which plate do ventral horns correspond to?
basal plate - somatic efferent and visceral efferent.
36
What are the divisions of the white matter in the spinal cord?
3 funiculi on each side; Dorsal funiculus - between shallow dorsal sulcus, extends deeply by median glial septum, and dorsal root of spinal nerves (right at top, next to ventral fissure). Lateral funiculus - between lines of dorsal and ventral roots. Ventral funiculus - between lines of ventral roots and ventral fissure.
37
What are funiculi?
Nerve tracts - contain ascending and descending tracts of nerve fibres. Grouped within bundles (fasciculi/tracts) of common origin, destination and function.
38
What are the 4 primary derivatives of the neural tube?
Prosencephalon (front brain) Mesencephalon (mid brain) Rhombencephalon (hind brain) Remainder of neural tube
39
What are the 2 subdivisions of the prosencephalon and their derivates and lumen?
Telencephalon (outer) - cerebral cortex, limbic system, basal nuclei (aggregation of ganglia) - lateral ventricles and corpus cascosum, hippocampus (caudate nuclei). Diencephalon (inter) - epithalamus (above), thalamus (middle), hypothalamus (below) - third ventricle.
40
Are their any subdivisions of the mesencephalon?
No, but the major derivatives are; Tectum (corpora quadrigemina) - 4 structures (2 rostral colliculi and 2 caudal colliculi). Tegmentum (mid section) Cerebral peduncles (feet). Lumen for all of these is the cerebral aqueduct.
41
What are the subdivisions of the Rhombenephalon and their major derivatives and lumens?
Metencephalon - Pons, Cerebellum Myelencephalon - Medulla oblongata (becomes spinal cord) Lumens are rostral part of 4th ventricle and caudal part of 4th ventricle.
42
What are the major derivatives of the remainder of the neural tube?
Spinal cord. Lumen is the central canal. No subdivisions.
43
What are gyri?
Hills in the brain
44
What are sulci?
Dips in the brain
45
What is the forebrain?
The prosencephalon
46
What are the 3 components of the Prosencephalon?
Rhinencephalon - olfactory bulbs, hippocampus Telencephalon - paired cerebral hemispheres, basal nuclei, corpus striatum. Diencephalon - most rostral part of brain stem, thalamus (central), epithalamus (dorsal) and hypothalamus (ventral - will be only visible part in intact brain).
47
Discuss the telencephalon.
Paired cerebrum and basal nuclei. Corpus striatum - alteration of this nuclei with fibers in which they are embedded. Deep to cerebral cortex. Defects - huntingtons disease and parkinsons disease.
48
Where is CSF produced?
In the choroid plexus
49
What is the corpus striatum?
Consists of Basal ganglia and its components; Caudate nucleus, Putamen, Claustrum, Amygdaloid body. And the internal capsule. The corpus striatum, or "striped body" consists of the basal ganglia (basal nucleus) and the internal capsule. The basal ganglia is made up of neurons, so it is gray matter. The internal capsule is a group of tracts surrounded by myelinated axons, so it is white. Because the internal capsule runs between the caudate and lenticular nucleus of the basal ganglia, the group of structures looks striped. The area is called the corpus striatum (striped body). The blood supply is from the striata artery. This thinly lined artery is calledy the "artery of stroke" because it ruptures easily if blood pressure is too high.
50
Discuss the Diencephalon.
Derived from the prosencephalon. Consists of thalamus; central, relay centre for nerves connecting cerebral hemspheres to brain stem and spinal cord. Epithalamus; dorsal, pineal gland (melatonin), regulates diurnal and other rhythms and sleep, influences seasonal breeding. Hypothalamus; ventral, near 3rd ventricle, part of visceral NS. Controls biological rhythms (appetite, water balance, body temp., cardiovascular, sexual, sleep, muscle tension, emotion). Nuclei of autonomic activities and behaviour. Attached ventrally is the hypophysis (pituitary gland - dark, solid body). Neural connection to hypothalamus and hypophysis is critical to integration of neural and endocrine systems. Important regulatory centre. Contains neurosecretory cells - hormonal control (temp., osmolarity, emotions). Integrative centre for sensory inputs and relay centre for channeling. Relays sensory info to cortices and motor info to spinal cord.
51
Discuss the rhombencephalon.
3 main components; cerebellum/dorsal metencephalon (craniodorsal), pons/ventral mentencephalon (cranioventral), and medulla oblongata/myelencephalon (caudal, cranial continuation of spinal cord, contains autonomic centres and nuclei of cranial nerves). Function is evolutionary (most primitive part of brain). All sensory (except vision and smell) and nearly all motor neurons pass through this area. Has sensory synapses for control of balance and movement reflex activities (proprioception) and simple auditory reflexes. Nuclei control respiration, the heart (vasoconstriction), swallowing and vomiting. Most of control of movement and equilibrium in the cerebellum.
52
What is the mesencephalon?
Mid brain - between pons and diencephalon. Short, rather constricted portion that better preserves the basic organisation of the neural tube compared to other parts of the brain stem. Main structures are the tectum (dorsal to aqueduct, 4 rounded surface swellings; 2 caudal and 2 rostral colliculi). Tegmentum (core of midbrain, directly continuous with corresponding stratum of metencephalon. Cerebral crus (peduncle).
53
What is the tectum?
4 round swellings (colliculi), dorsal to the aqueduct. Left and right rostral (coordinate visual reflexes) and left and right caudal (analysis and relay of nuclei of auditory information).
54
What is the tegmentum?
Core of the midbrain. Site of nuclei of oculomotor nerve. Vascularity for the red nuclei/nerves. Substantia nigra - accumulation of pigment (prominent lamina, darker colour). Associated with basal nuclei (voluntary movement).
55
What are the cerebral peduncles?
Paired ventrally, they contain both sensory and motor tracts and have large bundles of nerves that connect the spinal cord/brain stem with cerebral hemispheres. Oculomotor nerve emerges directly rostral to the pons in this region. Fibre tracts emerge from telencephalon, converge, separate through interpeduncular fossa and converge again.
56
What are the Major blood vessels supplying the Spinal Cord?
3 main arteries; vertebral (occipital lobes), ventral spinal artery (largest), and dorsolateral spinal arteries (paired). Veins; Epidural venous plexus, Vertebral venous plexus (runs length of vertebral column and drains blood from vertebrae, thin walled, no valves).
57
What are the major blood vessels supplying the brain?
15-20% of cardiac output is used to supply the brain. Main arteries; internal carotid, basilar, and circle of willis (blood supply to brain mainly via circulus arteriosus cerebri/circle of willis. Forms ring around infundibular stalk (ventral to hypothalamus).
58
What are meninges?
Protective surface that encases brain and spinal cord. 3 layers; duramater (tough, outermost, fused with inner periosteum), arachnoidmater (spidery, web like), and piamater (thin, directly attached to brain and cord). All these structures have a nurturing role.
59
Where is the epidural space?
Between the skull/vertebrae and dura. | Often filled with fat.
60
Where is the sub-arachnoid space?
Between the arachnoid and the pia. | Contains CSF, wider than sub-dural space but less uniform, widest parts known as cisterns.
61
What are the brain cavities?
Hollow cores that are continuations of the neural canal, communicating cavities, also produces CSF that bathes the whole CNS. Lateral ventricles - reached via the interventricular foramina in the L and R telencephalon. Third ventricle (III) - lumen of the diencephalon, mesencephalic aqueduct from lumen of the mesencephalon. Fourth ventricle (IV) - lumen of the rhombencephalon, opens into the meningeal space surrounding the neural tube through the lateral aperture (caudolateral to cerebellum). Central canal of the spinal cord.
62
What is CSF?
Cerebro-spinal fluid. High conc of K and Ca ions, lower Na, Mg and Cl than plasma. Contains little glucose and protein as barrier is impermeable to larger molecules (including antibiotics and other drugs). Sites of production (dogs); choroid plexi in lateral third (35%), choroid plexi in fourth ventricle (23%), ependymal linings of the ventricles, piamater membrane over brain, blood vessels in the sub-arachnoid space (43%). Produced as an exudate via active secretion. Fluid exudes through the capillary endothelium and is transported across the blood brain barrier. Constant production; 30mL/hr. Bathes brain and cord before returning to blood via the arachnoid granulations (villi in venous sinus).
63
What are the functions of CSF?
Protects, nourishes and assists homeostasis. Provides mechanical protection, modulates intracranial pressure, and chemically buffers the CNS (creates stable environment). Transports metabolites, nutrients, and endocrines/neurotransmitters. Better ionic concentration and pH stability.
64
What is meningitis?
Inflammation of the meninges. | Severe disruption, neurological defects and often death.
65
What are the 3 main groups of cranial nerves?
Special senses; olfactory, optic, vestibulocochlear. Head muscles of somatic origin; oculomotor, trochlear, abducent, hypoglossal. Pharyngeal arch origin structures; trigeminal, facial, glossopharyngeal, vagus, accessory.
66
What do the nuclei of the cranial nerves represent?
the continuation of the 4 functional components of grey matter; somatic afferent, visceral afferent, visceral efferent, somatic efferent. They are also supplemented by two additional components; special somatic afferent and special visceral afferent (appear in medulla oblongata in connection with innervation of structures of the head and have no counterparts in trunk or limbs).
67
Can cranial nerves contain more than one functional component?
Yes, they can contain more than one functional component that arises from more than one nucleus. Meanwhile, certain nuclei give rise to similar components of more than one nerve.
68
Where are the nuclei of cranial nerves present?
In the Myelencephalon, pons, mesencephalon (III, IV) and the prosencephalon (I and II).
69
Where are the nuclei of CNIII and CNIV present?
In the Mesencephalon.
70
Where are the nuclei of CNI and CNII present?
In the prosencephalon.
71
What are the two special fibre types of cranial nerves?
Special somatic afferent (SSA) - vision and hearing | Special visceral afferent (SVA) - olfaction and taste
72
What are the 4 fibre types of cranial nerves?
General somatic afferent (GSA) - face, mouth. General visceral afferent (GVA) - pharynx, larynx. Somatic efferent (SE) - skeletal (trigeminal, facial, nucleus ambigulus). Visceral efferent (VE) - parasympathetic (vagus). Afferent = sensory, Efferent = motor.
73
What is a mixed nerve?
Sensory and motor.
74
What is the olfactory nerve primarily concerned with?
smell
75
What is the optic nerve primarily concerned with?
vision
76
What is the abducent nerve primarily concerned with?
lateral gaze
77
What is the vestibulocochlear nerve primarily concerned with?
hearing, balance
78
What is the glossopharyngeal nerve primarily concerned with?
tongue | pharynx
79
What is the accessory nerve primarily concerned with?
muscles of the neck
80
What is the hypoglossal nerve primarily concerned with?
movement of the tongue
81
Discuss CNI.
``` Olfactory Action: smell, fibre type is SVA (sensory). Brain origin: Olfactory bulbs No branches. Foramen: cribiform plate ```
82
Discuss CNII.
Optic Action: vision, fibre type is SVA (sensory). Brain origin: Diencephalon Branches/Features: Nerve tract, optic chiasma. Foramen: optic foramen
83
Discuss CNIII.
``` Oculomotor Action: Motor to intrinsic eye muscles - dorsal, ventral and medial rectus. Ventral oblique. Motor to intrinsic eye muscles - ciliary, body and iris. Associated with parasympathetic ciliary ganglion. Brain origin: Midbrain No branches. Foramen: Orbital fissure ```
84
Discuss CNIV.
Trochloear Nerve Smallest, only nerve that emerges from brain stem dorsally, decussates. Action: motor to extrinsic eye muscles (dorsal oblique) Brain origin: Midbrain No branches. Foramen: Orbital fissure
85
Discuss CNVI.
Abducent Nerve Fibres originate within caudal brainstem. Action: Motor to extrinsic eye muscles (lateral rectus and retractor bulbi) Brain origin: Hindbrain No branches. Foramen: Orbital fissure
86
Discuss CNV.
Trigeminal Nerve. Largest of the cranial nerves. Sensory to face. Brain origin: Hindbrain Branches: 1. Opthalmic 2. Maxillary 3. Mandibular Foramen: 1. Orbital fissure 2. Round F-alar canal 3. Oval foramen Action: 1. Sensory - branches into lacrimal, frontal and nasociliary nerves, orbit, cornea, eyelids, nasal mucosa and skin medial to eye. 2. Sensory - both lids, upper jaw, teeth, lips, nasal. 3. Sensory and motor - lower jaw, teeth, tongue, temporal skin, innervates muscles of mastication. Innervates tensor tympani (muscle to malleus).
87
Discuss CNVII.
Facial Nerve. Facial expression, taste, secretions (saliva, lacrimal, nasal). Brain origin: Hindbrain Branches; Stapedius nerve, dorsal and ventral buccal nerves, auriculopalpebral nerve, cervical nerve. Foramen: Internal acoustic foramen, stylomastoid foramen. Action: Motor and sensory; Motor to stapedius m. (middle ear), caudal belly of digastricus (mastication), nasal and lacrimal glands, salivary glands (sublingual and mandibular-associated with PNS). Sensory to rostral 2/3rds of tongue, chorda tympani, lingual n., rostral surface of pinna. Paralysis of this nerve can result in pain with loud noises.
88
What are the consequences of trigeminal nerve injury?
Sensory deficiencies - manifested by facial irritation. Lesion of mandibular N. - paralysis of jaw muscle. Dropped jaw in dogs - idiopathic bilateral paralysis of musculature.
89
What occurs with facial nerve injury?
Depends on site of lesion. Central lesion: affects whole facial field. Loss of secretory activity of salivary and lacrimal glands (except parotid). Lesion auriculopalberal - drooping of external ear and narrowing of palpebral fissure. Buccal branches - paralysis of muscle of jaw and cheeks.
90
Discuss CNVIII
``` Vestibulocochlear nerve Brain origin: Hindbrain Foramen: Internal acoustic foramen Branches: Vestibular and cochlear. Action: Hearing and balance, special sensory. ```
91
Discuss CNIX.
Glossopharyngeal nerve. Brain Origin: Hindbrain (ventrolateral aspect of medulla oblongata). Foramen: Jugular foramen Branches: Pharyngeal, carotid sinus, lingual. Action: Sensory and motor. Sensory - pharynx, middle ear, carotid sinus and body, caudal 1/3rd of tongue. Motor - parotid and zygomatic salivary glands, pharyngeal m. Associated with PNS otic ganglion.
92
What are the 4 cranial nerves that have parasympathetic pathways?
Oculomotor (III) - cilary ganglion to cilary smooth muscle and iris constrictor. Facial - mandibular and pterygopalatine ganglion to sublingual and mandibular glands and lacrimal and nasal glands respectively. Glossopharyngeal - otic ganglion to zygomatic and parotid glands. Vagus - goes to heart and GIT.
93
Discuss CNX.
Vagus nerve. Vagus and sympathetic nerves part at entrance to chest, vagus continues horizontally through mediastinum until it divides over the pericardium into dorsal and ventral branches. These become the dorsal and ventral vagaries trunks that enter the abdomen along with the oesophagus. Most widespread cranial nerve. Brain origin: Hindbrain Foramen: Jugular Branches: Auricular n., pharyngeal, cranial laryngeal, left and right vagus, recurrent laryngeal, cardiac branches, pulmonary branches, dorsal and ventral vagal branches. Action: Sensory and motor. Sensory - external ear (external auditory meatus), pharynx, larynx. Motor - laryngeal m., pharyngeal m., oesophagus. Sensory and motor to thoracic and abdominal viscera. Proximal ganglia - auricular N. branches of CNV (external ear). Distal ganglia - cranial laryngeal N. cricothyroideus m., laryngeal mucousa, epiglottis, taste buds. Caudal to distal ganglia the vagus runs along with the sympathetic trunk (vagosympathetic trunk).
94
What happens to the vagus nerve at the thoracic inlet?
Vagus separates into sympathetic trunk. | Branches innervate the heart via cardiac nerves.
95
What does the vagus nerve do at the hilus of the lungs?
Branches to bronchi. Main nerve continues along with oesophagus and branches into dorsal and ventral branches just caudal to the heart.
96
Where does the dorsal vagal trunk go?
courses along the celiomesenteric plexus.
97
Where does the ventral vagal trunk go?
innervates the liver and lesser curvature of the stomach.
98
How far caudally does the vagus nerve reach?
As far caudally as the left colic flexure. | Supplies digestive tract and associated organs up to this point.
99
Discuss CNXI.
Accessory nerve. 2 roots; spinal (runs cranially through foramen magnum where it approaches cranial root, merges, splits again, and then goes on to form accessory n.) and cranial (amalgamates with vagus). Brain Origin: Hindbrain Foramen: Jugular foramen. No branches Action: Motor - brachiocephalicus, omotransversarius, trapezius.
100
Discuss CNXII.
Hypoglossal nerve. Brain origin: Hindbrain Foramen: Hypoglossal foramen Branches: None Action: Motor to intrinsic and extrinsic muscles of tongue. Leaves ventral aspect of medulla oblongata before passing through hypoglossal canal and then nerves of vagus group. Reaches tongue where it enters ventrally to glossopharyngeal nerve. Innervates tongue via hypoglossal foramen. Motor to styloglossus, hyoglossus, genioglossus and intrinsic musculature.
101
What is the longitudinal fissure?
Gap separating the two cerebral hemispheres.

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