Nervous System Flashcards

1
Q

nervous system

A

CNS + PNS

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1
Q

CNS

A

brain + spinal cord

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2
Q

brain

A

forebrain
midbrain
hindbrain

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3
Q

PNS

A

cranial nerves
spinal nerves
peripheral ganglia

somatic + autonomic

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4
Q

SNS

A

motor + sensory

control of body wall + upper/lower extremities

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5
Q

ANS

A

visceral
motor + sensory

motor → symp. + parasymp

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6
Q

cells in NS

A

neurons: nerve cells that conduct signals
neuroglia: support cells for neurons

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7
Q

neuron

A

~ 100 billion neurons (10^11)
each one has ~ 100 000 connections with other neurons

cell body = nucleus, nucleolus, dendrites, mitochondria, Nissl bodies
1 axon leaves cell body

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8
Q

synapse

A

connections between neurons
10^15 in CNS

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9
Q

nerve cell bodies

A

nucleus: collection in CNS
ganglia: collection in PNS

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10
Q

Nissl bodies

A

specialized ribosomal bodies
specific to nerve cells

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11
Q

neurofibrils

A

intermediate filament proteins
provide support within axon hillock

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12
Q

axon hillock

A

initial segment
summation of excitatory + inhibitory input
if threshold potential is reached = fires

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13
Q

bipolar neuron

A

2 appendages = 1 dendrite + 1 axon
senses = vision, taste, olfaction

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14
Q

unipolar neuron

A

1 appendage
somatosensation (afferents)

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15
Q

multipolar neuron

A

many dendrites, one axon
efferents (motor)

pyramidal, purkinje, stellate, granule, basket cells → found in brain = different dendrite branching

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16
Q

satellite cells

A

neuroglia that surround cell bodies in ganglia (PNS)
regulate O2, CO2, nutrient, + NT levels around neurons

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17
Q

Schwann cells

A

neuroglia that surround axons in PNS
one cell wraps one section of axon + produces myelin sheath = participate in repair process after injury

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18
Q

oligodendrocytes

A

neuroglia that myelinate CNS axons
have appendages = one cell myelinates many whole axons
provides structural framework

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19
Q

astrocytes

A

neuroglia in CNS
provide structural support; regulate ion, nutrient, + dissolved gas concentrations; absorb + recycle NT; form scar tissue after injury
some maintain blood-brain barrier

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20
Q

ependymal cells

A

neuroglia in CNS
line ventricles + spinal cavity
assist in producing, circulating, and monitoring of CSF

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20
Q

microglia

A

neuroglia in CNS
circulate to remove cell debris, wasts, and pathogens by phagocytosis (substitute for blood = limited by BBB)

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21
Q

meninges

A

membranes covering CNS structures = protection
- dura mater: tough outer layer; protect from external force
- arachnoid mater: secretes CSF into subarachnoid space; covers cranial blood vessels
- pia mater: delicate covering of brain

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22
Q

cerebrum

A

higher cognitive functions
language + speech
somatic motor + sensory function
regulates emotional aspects of behaviour

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23
cerebral cortex
outside surface grey matter neuronal cell bodies
24
cerebral medulla
inner region white matter axons
25
longitudinal fissure
interhemispheric separates L + R hemispheres
26
poles of cerebrum
frontal pole occipital pole 2 temporal poles (L+R)
27
sulci
central sulcus = separates pre + post central gyri lateral sulcus = separates temporal lobe
28
frontal lobe
higher cognitive planning, strategy, motor
29
parietal lobe
perception of self in space, sensory
30
temporal lobe
memory, learning, social, hearing
31
occipital lobe
vision = most important sense
32
precentral gyrus
frontal lobe primary motor cortex = initiation of motor signals - motor homunculus - map on cortex corresponding to body anterior to central sulcus
33
postcentral gyrus
parietal lobe primary sensory cortex - sensory homunculus - map on cortex corresponding to body posterior to central sulcus
34
projection fibres
travel to and from cortex ex. to/from spinal cord
35
association fibres
intrahemispheric connections - short ex. within lobe - long ex. between lobes → BA to WA for speech
36
commissural fibres
interhemispheric connections ex. corpus callosum = largest
37
cerebellum
acts as a comparator = compares intended movement with evolving movement and corrects for errors → uses feedback to make adjustments ensures movements are smooth, coordinated, and purposeful (skilled) regulates posture + balance
38
cerebellar ataxia
intention tremor, lack of balance + coordination
39
brainstem
midbrain, pons, medulla oblongata contains motor + sensory pathways connecting cerebral cortex + thalamus to SC houses cranial nerve nuclei (origins of CNs) contains RAS = arousal + consciousness vital centres for regulating heart rate + breathing centres for regulating swallowing + gag reflex
40
diencephalon
thalamus: inferior to corpus callosum; bilateral structure hypothalamus: inferior to thalamus
41
midbrain
substantia nigra + red nucleus relay centres for visual and auditory pathways (reflexive orientation) CNs III + IV attached
42
substantia nigra
regulates motor activity neuronal degeneration = Parkinson's disease
43
red nucleus
regulates motor activity active controller of flexors of upper extremities controlled by descending inhibition
44
pons
bridge between cerebrum + cerebellum CNs V, VI, VII, VIII attached
45
medulla oblongata
contains vital cardio-respiratory regulatory centres nuclei for CNs IX, X, XI, XII
46
ventricles
lumen of neural tube during development fluid from capillary beds = CSF → circulates within brain
47
lateral ventricles
have anterior + posterior horns connect to 3rd ventricle
48
3rd ventricle
separates L + R thalamus feeds into cerebral aqueduct = connects to 4th ventricle
49
4th ventricle
between pons and cerebellum feeds into central canal within SC
50
internal carotid arteries
paired ascend carotid canals divide into anterior + middle cerebral arteries
51
vertebral arteries
branch from subclavian arteries ascends through foramen magnum L+R join at pons → basilar artery → posterior cerebral arteries
52
anterior cerebral artery
branches from internal carotid, forms anterior of Circle of Willis supplies medial + dorsal brain
53
anterior communicating artery
bridges L+R anterior cerebral arteries
54
middle cerebral artery
from internal carotid, extends laterally supplies lateral brain
55
posterior cerebral artery
from basilar, extends laterally forms posterior of Circle of Willis supplies posterior and ventral brain
56
posterior communicating arteries
connects posterior + middle cerebral arteries (2; one on each side) forms sides of Circle of Willis
57
spinal cord
within vertebral column projection pathway to/from cerebral cortex; extends from medulla at foramen magnum ends as conus medullaris at L1-2 intervertebral disc bulges in lower cervical (brachial plexus) + lumbar (lumbosacral plexus) segments = roots of spinal nerves for upper/lower extremities
58
central canal
within SC; passes through centre of grey matter continuous with ventricles of brain
59
cauda equina
nerve roots extending from SC; lie inferior growth to maintain attachment between SC and vertebral column during development (VC grows faster)
60
filum terminale
pia matter continues past SC attaches cord to coccyx = stabilizing ends at S2 vertebral level
61
spinal cord organization
inner grey matter - dorsal (sensory) horn → dorsal root - ventral (motor) horn → ventral root outer white matter = axon tracts dorsal + ventral roots join = spinal nerve posterior median sulcus; anterior median fissure
62
sensory + motor info
continuous flow between brain, SC, peripheral nerves + organ systems millions of neurons deliver incoming + outgoing info
63
pathways between CNS + PNS
ascending + descending consists of a chain of neurons + associated cell bodies (nuclei or ganglia)
64
somatic sensory pathways
dorsal column/medial lemniscal spinothalamic spinocerebellar
65
dorsal columns
proprioception + discriminant touch receptor → 1st order neuron ascends ipsilaterally → medulla = synapse on 2nd order neuron → crosses in brainstem
66
fasciculus cuneatus
upper dorsal column formed by upper extremities + trunk corresponds to nucleus cuneatus in midbrain
67
fasciculus gracilis
lower dorsal column formed by lower extremities + trunk corresponds to nucleus gracilis in midbrain
68
medial lemniscus
2nd order neuron ascends from brainstem through midbrain to thalamus (ipsilaterally) synapses on 3rd order neuron in ventral nuclei of thalamus
69
thalamocortical projections
3rd order neurons project from thalamus to S1 (homotopic = cortex mapped according to receptor region)
70
spinothalamic pathway
pain + temp; deep touch receptor → 1st order neuron enters dorsal horn = synapse on 2nd order neuron → crosses in SC + ascends → thalamus
71
anterior spinothalamic tract
deep touch (crude - non-discriminative) = itch, pressure 2nd order neuron crosses midline of SC from dorsal horn to anterior (white matter)
72
lateral spinothalamic tract
pain + temp 2nd order neuron crosses midline of SC from dorsal horn to lateral (white matter)
73
spinocerebellar pathway
unconscious proprioception from trunk + extremities receptor → 1st order neuron enters dorsal horn = synapses on two 2nd order neurons → anterior + posterior tracts
74
posterior spinocerebellar tract
2nd order neuron stays ipsilateral → projects through pons to cerebellum
75
anterior spinocerebellar tract
2nd order neuron crosses in SC → projects to pons = crosses over back to ipsilateral pons → cerebellum
76
somatic motor systems
CNS sends motor commands → distributed to body by PNS effect contraction of skeletal muscle pathways involve at least 2 motor neurons: upper + lower
77
upper motor neuron
cell body is in CNS processing centres (M1) influences LMN: sends descending signal to excitatory/inhibitory synapse
78
lower motor neuron
cell body is in ventral horn of SC or motor CN nucleus in brainstem axon extends to skeletal muscle = Common Final Pathway
79
UMN lesion
cannot pass signal if inhibitory synapse = disinhibition of LMN = spastic paralysis (continuous, uncontrolled firing leads to rigidity)
80
LMN lesion
signal cannot reach periphery no response = flaccid paralysis → tone cannot be monitored (no feedback)
81
motor pathways
corticospinal pathway (pyramidal) corticonuclear pathway (corticobulbar)
82
corticospinal pathway
UMNs descend from cerebral cortex (M1 + S1) through crus cerebri (midbrain) and pyramids (anterior medulla) → SC = synapse on LMN in ventral horn (somatic motor nuclei) → muscles in limbs + trunk bundle of fibres (~1m) originating from pyramidal neurons in cortex from 3 main areas: M1, PMC + SMA, S1 regulates distal limb muscles → precise, skilled, learned movements
83
corticonuclear pathway
UMNs extend from cerebral cortex (M1) → motor CN nuclei in brainstem = synapse on LMN → head + neck muscles
84
extrapyramidal pathways
subsidiary descending pathways important as backup systems
85
basal ganglia + cerebellum pathways
modulate + modify activity in corticospinal tract to ensure smooth, coordinated, purposeful movement
86
central motor program
production of voluntary movements - incoming sensory info is conveyed to posterior parietal cortex via association fibres - posterior parietal cortex = process info to identify + localize targets in space - PMC + SMA = formulation of plan of action - M1 = execution of movement through desc pathways
87
simple finger flexion
activates: - M1 = effect movement - S1 = receive feedback about movement
88
finger movement sequence (performance)
activates: - M1 + S1 - premotor + supplementary motor area = activity prior to movement + during (planning sequence)
89
finger movement sequence (mental rehearsal)
activates: - only premotor + supplementary motor area
90
lateral corticospinal pathway
85% of UMN axons cross at pyramids in inferior medulla = contralateral path to SC
91
anterior corticospinal pathway
15% of UMN axons stay ipsilateral at pyramids in medulla cross midline in SC (at level they leave to periphery)
92
internal capsule
area of bundled axons of corticospinal path in brain supplied by small arteries
93
UMN lesion ex. corticospinal pathway
- middle cerebral artery stroke or injury to internal capsule = lose all corticospinal input - brainstem lesion = decorticate or decerebrate posture - spinal cord injury = lose UMN output = spastic paralysis in contralateral limb
94
decorticate posture
no inhibitory control of upper extremity muscles = flexion lesion above level of red nucleus stiff, legs out straight, arms flexed across chest
95
decerebrate posture
inhibitory control is present to prevent flexion = extensor muscles are active lesion below level of red nucleus all limbs extended and held stiff
96
LMN lesion ex. corticospinal pathway
spinal nerve injury → lost downstream flow = flaccid paralysis
97
SNS
supplies body wall structures (skin, muscle, bone, parietal membranes) motor functions: skeletal muscle = voluntary control (exception: reflex arc) sensory functions: pain, temp, touch, proprioception
98
ANS
supplies viscera (glands, smooth muscle, cardiac muscle, visceral membranes) → involuntary control motor functions: symp + parasym → balance sensory functions: visceral afferents → pain (indirect or referred)
99
spinal nerves
emerge from SC → out to periphery = supply peripheral structures 31 pairs: 8C, 12T, 5L, 5S, 1C dorsal + ventral root together bifurcates into ventral + dorsal primary rami (end of SN)
100
cervical spinal nerves
nerve emerges superior to respective vertebrae (C8 n. = inferior to C7 vertebrae) all downstream nerves (T-Coccygeal) emerge inferior to respective vertebrae
101
general afferents
carry sensory info to SC - somatic afferents (GSA) = PTTP from body wall - visceral afferents (GVA) = pain, distention, chemical from visceral structures
102
general efferents
emerge from SC + carry motor info away - somatic efferents (GSE) = motor neurons in ventral horn projecting to skeletal muscles - visceral efferents (GVE) = autonomic fibres innervating smooth muscle, cardiac muscle, glands
103
intermediate zone
lateral horn (grey matter) in sc at levels T1-L2 = symp. preG cell bodies autonomic
104
dorsal primary ramus
feeds through muscle supply muscle + reach subcutaneous space → posterior cutaneous branch = sensation to skin only back (stops at scapula)
105
ventral primary ramus
continues all around body wall lies between muscles that form wall supplies all body wall muscle (all plexi) lateral cutaneous branch: formed by branching at mid-axillary line anterior cutaneous branch: formed by branching at midline
106
dermatome
innervation of entire strip of skin around body wall by spinal nerve = segmented pattern along body (on all 4s) VPR follows extremities T4 = nipples T10 = umbilicus
107
intervertebral foramen
opening between vertebrae where spinal nerve emerges
108
vertebral canal
down middle of spinal column where spinal cord is
109
nerve
covered by epineurium contains fascicles + blood vessels grow slowly
110
fascicles
bundle of axons going to area of body individually covered by perineurium (membrane)
111
nerve axons
covered by endoneurium = integrity make up fascicles
112
reflex arc
short circuit information pathway 1. stimulus = activation of receptor 2. activation of sensory neuron 3. info processing in CNS (interneuron) 4. activation of motor neuron 5. response by effector info still travels to brain
113
somatic nerve plexuses
formed by ventral spinal rami - at thoracic level → follows ribs - above + below thoracic → nerves aggregate to form plexus
114
brachial plexus
supplies upper extremities VPR of SNs C5, C6, C7, C8, T1 → 5 main nerves: axillary, median, musculocutaneous, radial, ulnar
115
lumbar plexus
lower anterior abdominal wall medial + anterior thigh inguinal region (groin) VPR of SNs L1, L2, L3, L4 → 6 main nerves: iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator
116
cremasteric reflex arc
formed by ilioinguinal + genitofemoral nerves (lumbar plexus)
117
lumbosacral plexus
gluteal region lower extremities (except ant. med. thigh) perineal region + genitals VPR of SNs L4, L5, S1, S2, S3 → 6 main nerves: tibial, common peroneal, superior gluteal, inferior gluteal, pudendal, posterior femoral cutaneous
118
autonomic motor system
controlled by hypothalamus → output to pons + medulla neurons synapse in periphery before target site (next to vertebral column) = 2 neuron system - preG fibre: from CNS → autonomic ganglion - postG fibre: from ganglion → effector site
119
sympathetic autonomic motor nerves
GVEs thoracolumbar (SC levels) T1-L2 (lateral horn in grey matter = symp preG nerve cell bodies → synapse in symp ganglion on post G fibre) fight or flight + fright
120
parasympathetic autonomic motor nerves
GVEs craniosacral - CN III, VII, IX, X - S2, S3, S4 preG neurons extend from CNS to ganglion near target rest, relax, regenerate
121
sympathetic NS
SNs (T1-L2)→ symp. ganglia → symp. nerves → targets
122
sympathetic chain ganglia
secondary pathway collection of ganglia linked together by axons passing between distribute symp. info up + down for postG supply to supradiaphragmatic organs break at T5
123
splanchnic nerve
preG fibres pass through symp. ganglia without synapsing and join to form nerve nerve extends to prevertebral ganglia = close to visceral targets → synapse with postG fibres supply visceral organs (subdiaphragmatic)
124
sympathetic actions
eye: pupil dilation salivary glands: thick viscid secretion trachea + bronchioles: dilation heart: ↑ rate + contractility ureters + bladder: relax detrusor m. (wall of bladder) + contract trigone + sphincter gastrointestinal: ↓ motility + tone; contract sphincter genitalia: ejaculation + relaxation of uterus blood vessels: dilation in skeletal muscle; constriction in viscera
125
parasympathetic NS
no control to the skin CNs III, VII, IX, X → preG to terminal ganglia = synapse on postG → targets pelvic splanchnic nerves → preG to targets = synapse on postG → effect
126
parasympathetic actions
eye: pupil constriction; accomodation reflex lacrimal gland: stimulate tears salivary glands: copious watery secretion trachea + bronchioles: constrict; ↑ secretion heart: ↓ rate + contractility ureters + bladder: contract detrusor m.; relax trigone + sphincter gastrointestinal: ↑ motility + tone genitalia: stimulates erection
127
subcutaneous structures
supply to skin from SN, enters symp. chain via white ramus → synapse on postG → leave through grey ramus back to SN
128
supradiaphragmatic organs
preG lateral horn (T1-T5) ventral root → SN → ganglion → up/down symp. chain synapse on different postG → goes straight to organ - heart = cardiac nerve - lungs = pulmonary nerve
129
subdiaphragmatic organs
preG fibre leaves SN via white ramus to ganglion but doesn't synapse → pass through symp. ganglion = forms splanchic nerves → synapse in prevertebral (collateral) ganglion associated with abdominal aorta where branch comes off postG follows blood vessel
130
general visceral afferents
autonomic sensory info follows same pathway as motor info ex. splanchic n. → symp. ganglion → white ramus → SN → dorsal root ganglion
131
referred pain
pain in visceral structures → referred to body wall through dermatomes ex. appendix - T10 symp. level → swelling = interpreted as pain at T10
132
cranial nerves
emerge from area of brainstem 12 pairs (exception of X) run functions of head + neck arise from + interact with nuclei in brainstem cell bodies of sensory neurons = in CN ganglia
133
CN I
olfactory nerve pure sensory = olfaction
134
olfactory nerve path
receptors on roof of nasal cavity → olf. epithelium = supplied by olf. nerve filaments → pass through cribiform plate, terminate in olf. bulb → olf. tract → primary olf. cortex in temporal lobe (bypass thalamus)
135
damage to olfactory nerve
hyposmia / anosmia = ↓ sense of smell
135
CN II
optic nerve pure sensory = vision
136
optic nerve path
retinal receptors → bipolar → amacrine → ganglion cells = axons → optic nerve optic nerve → optic chiasm → tract → LGN → V1 VFs projected onto V1 inverted + reversed V1 = medial occipital, along calcarine fissure
137
damage to optic nerve
visual field defects
138
CN III
oculomotor nerve from midbrain mixed nerve - somatic motor → extraocular muscles - parasymp. → pupillary constriction + accomodation (ciliary ganglion)
139
oculomotor nerve path
superior division: - superior rectus + levator palpebrae mm. inferior division: - medial rectus + inferior rectus + inferior oblique mm. - carries preG parasymp. info to ciliary ganglion → pupillary constrictor + ciliary + medial rectus mm.
140
damage to oculomotor nerve
pupillary dilation ophthalmoplegia (weakened eye movements)
141
CN IV
trochlear nerve from midbrain (posterior) smallest CN; longest intracranial path pure motor = superior oblique m.
142
damage to trochlear nerve
isolated = uncommon protected by double layer of dura
143
CN VI
abducens nerve pure motor = lateral rectus m. (abduction of eye) at ponto-medullary junction (anterior surface of pons)
144
damage to abducens nerve
vulnerable to injury in head trauma/ ↑ intracranial pressure damage = paralysis of muscle → deviation of eye medially (strabismus) = double vision (diplopia)
145
CN V
trigeminal nerve chief sensory nerve to face 3 branches from trigeminal ganglion mixed nerve = sensory + motor conduit for parasymp. functions of CNs III, VII, IX
146
damage to trigeminal nerve
mainly V2, V3 trigeminal neuralgia (tic Douloureux) very painful
147
V1
ophthalmic nerve eye = pure sensory → supraorbital nerves ciliary ganglion = parasymp. relay from CN III supplies superior corner of eye towards lambdic suture sensation to frontal + ethmoidal paranasal air sinuses sensory innervation (general sensation) to nasal cavity sensation to upper eyelid, side of nose, forehead + scalp
148
V2
maxillary nerve cheek = pure sensory → infraorbital nerves pterygopalatine ganglion = parasymp. relay for CN VII enters floor of orbit through inferior orbital fissure supplies corner of eye to corner of mouth sensation to: maxillary air sinus, nasal cavity, lower eyelid, skin of cheek, upper lip, maxillary teeth + gums
149
V3
mandibular nerve mandible somatic motor: → muscles of mastication sensory: → lingual nerve (submandibular ganglion = CN VII) → inferior alveolar nerve → mental nerve otic ganglion = parasymp. relay for CN IX
150
V3 functions
motor - muscles of mastication (4) sensory - lower lip, skin of mandible - mandibular teeth + gums (i.a. n.) - general sensation to anterior 2/3 of tongue (l. n.) - ends as mental n. - carries proprioceptive info from muscles of mastication to brainstem = force of bite
151
CN VII
facial nerve mixed nerve = somatic motor + sensory, parasympathetic attached to pons geniculate ganglion
152
facial nerve path
pons → geniculate ganglion - main branch = 5 → muscles of facial expression (temporal, zygomatic, buccal, mandibular, and cervical branches) - chorda tympani n. → submandibular ganglion - posterior auricular n. - greater petrosal n. → pterygopalatine ganglion
153
damage to facial nerve
partial taste, salivation, or lacrimation loss Bell's palsy = hemi-facial paralysis
154
facial nerve functions
motor - muscles of facial expression (5 branches) sensory - taste to anterior 2/3 of tongue (chorda tympani n.) - some sensory to skin around ear parasympathetic - lacrimal gland via pterygopalatine (V2) - submandibular + sublingual salivary glands via submandibular ganglion (V3)
155
CN VIII
vestibulocochlear nerve pure sensory - cochlear branch → organ of Corti - vestibular branch → vestibular apparatus
156
vestibular branch CN VIII
supplies vestibular apparatus (semicircular canals + vestibule) = balance and equilibrium disease: Meniere's syndrome (vertigo, nausea, vomiting)
157
cochlear branch CN VIII
supplies organ of Corti in cochlear = hearing bilateral central pathway in brainstem carries info to temporal lobe → primary auditory cortex damage: difficulty in localizing sound
158
CN IX
glossopharyngeal nerve mixed nerve = somatic motor + sensory, parasympathetic attached to medulla supplies tongue + pharynx; mediated gag reflex main branch → carotid sinus + pharyngeal branches + lingual branches branch → otic ganglion → parotid gland
159
damage to glossopharyngeal nerve
difficulty swallowing, loss of gag reflex (protection of airway)
160
glossopharyngeal nerve functions
motor - one muscle = stylopharyngeus (elevates pharynx) through lingual branch sensory (general) - posterior tongue, pharynx, palatine tonsils, carotid sinus + body sensory (special) - taste to posterior 1/3 of tongue parasympathetic - supplies parotid gland via otic ganglion (V3)
161
carotid sinus reflex
carotid stimulation = induce response to ↓ bp and pulse rate monitors bp + blood chemistry → feedback
162
CN X
vagus nerve mixed nerve = motor, sensory, parasymp. attached to medulla damage: difficulty in speech + swallowing
163
vagus nerve functions
motor - muscles of palate, pharynx, larynx (CN XI) sensory - muscles of palate, pharynx, larynx - sensory to eardrum - baroreceptor to hollow organs - carries visceral afferents from organs to CNS parasymp. - nerve for viscera - motor to smooth muscle in thoracic + abdominal organs up to distal transverse colon - regulates heart rate (↓)
164
CN XI
spinal accessory nerve motor only attached to medulla + upper SC damage = weakness when shrugging shoulders, turning head to side against resistance
165
cranial - spinal accessory nerve
extends from accessory root → accessory branch distributed by CN X to palate, pharynx, larynx (CN X sensory functions)
166
spinal - spinal accessory nerve
extends from spinal root → spinal branch supplies trapezius and sternocleidomastoid muscles in neck
167
CN XII
hypoglossal nerve pure motor attached to medulla supplies muscles of tongue (except stylopharyngeus) damage: inability to protrude tongue symmetrically
168