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Year 2: NeuroBiology > Lecture 8: CNs and Special Sensation > Flashcards

Lecture 8: CNs and Special Sensation Flashcards

1
Q

how is chemical sensation recognized

A

specialized cells directly detect chemical molecules

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2
Q

categories of chemical receptors by function

A

detect internal chemical stimuli or detect external chemical stimuli

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3
Q

chemical receptor that detects internal chemical stimuli and what it does

A

internal organ chemoreceptors

not consciously aware of them

track concentrations of O2, glucose, neuroactive hormones, and other substances

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4
Q

types of receptors that detect external chemical stimuli and where they each are located

A

gustatory/taste receptors: oral cavity

olfactory receptor neurone: nasal cavity

chemosensitive endings: via CN V (ss)

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5
Q

what types of stimuli do the chemosensitive endings detect

A

heat/coolness of menthol (mouth)

sting of amonia (nose and eyes)

somato and visceral sensory in digestive tract

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6
Q

describe the circumvallate papillae of the tongue

A

“surrounded by a wall”

posterior 1/3 of tongue/oropharynx

8-12 total, each has ~250 taste buds

CN IX for chemical and somatosensory stimuli

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7
Q

describe foliate papillae

A

“leaflike”

middle to posterior lateral tongue

10 on each side, each has ~100-150 taste buds

chemical stimuli: CN VII, IX, V

somatosensory: CN V, IX

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8
Q

describe the fungiform papillae

A

“mushroom shaped”

anterior 2/3 tongue/oral cavity

200-300 total, 2-5 taste buds each

chemical stimuli: CN VII, V

somatosensory: CN V

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9
Q

how large is the variability of total taste buds

A

> 100 folds

why some may like food more than others

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10
Q

describe the taste receptor cells

A

~100 in each taste bud

each lasts about 1-2 weeks then differentiate into new

have glial properties but NOT neuron

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11
Q

describe the glial properties of a taste receptor cell

A

microvilli with taste pores on tip

synapses with dendrites if CN VII, IX, and X at the base

can direct synapse with gap junctions via electrical synapse

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12
Q

what galnglia are involved in reception of taste signals

A

**ganglia of CN VII, IX, and X (gathering of somata of 1st order neurons

Geniculate ganglia of CN VII

Inferior ganglion of CN IX

Inferior ganglion of CN X

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13
Q

2nd order neurons for taste

A

all signals conducted to solitary nuclei

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14
Q

what are tastants

A

chemical molecules that transduce taste receptor cells

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15
Q

tastant receptors for salty

A

leaking ion channels for sodium/potassium ions

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16
Q

tastant receptors for sour

A

ionotropic channel with H+ depolarize

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17
Q

tastant receptors that detect sweet/umami/bitter

A

GPRC

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18
Q

what is the 6th taste

A

ammonium chloride

like salty or sour ion channels

helps you avoid toxic food

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19
Q

how do taste signals travel

A

graded potentials

no AP formed

release different neurotransmitters

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20
Q

describe the ipsilateral projection of the taste projection pathway

A

1st order = geniculate/inferior ganglia

2nd order = solitary nucleus; reciprocal projections with other structures

3rd order = VPM of thalamus

project from there to insular lobe

CN V chemical sensation is in the somatosensory path

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21
Q

what are the nuclei of the CN VII in the lateral pontomedullary junction

A

spinal trigeminal nucleus- somatosensory

facial motor nucleus - somatic motor

solitary nucleus - visceral sensory (mission completed)

superior salivatory nucleus - visceral motor

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22
Q

where does CN VII exit

A

exits internal acoustic meatus and terminal branches through the stylomastoid foramen

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23
Q

terminal branches of CN VII (somatic motor component)

A

temporal
zygomatic
buccal
mandibular
cervical
posterior auricle

Two Zebras Bite My Cookies

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24
Q

what nerve contributes to superficial innervation for facial expression and facial and scalp muscles

A

CN VII

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25
what pierces the buccinator
parotid gland duct
26
where do the dorsal and ventral nuclei components of the facial somatic motor nucleus receive projections from and what areas do they control respectively
dorsal nucleus: projections from bilateral anterior cingulate cortex (ACC), forhead and scalp ventral nucleus: projections from contralateral cerebral cortex except ACC, lower face
27
describe how S&S would be different between a LMN injury of CN VII vs UMN injury
UMN -can still wrinkle forehead -facial expression when they find something funny, but not if asked to smile LMN -whole side of face flaccid- Bell's palsy -no facial expression under any circumstances
28
purpose of the external ear
collect and conduct sound waves through air
29
function of middle ear
turn sound waves to vibration (both are mechanical waves)
30
what does the middle ear include
tympanic cavity: tympanic membrane ossicles: malleus, incus, stapes muscles: tensor tympani (CNV), stapedius (CN VII); function to decrease vibration
31
what is hyperacusis
caused by functional loss of muscles of middle ear
32
what makes up the inner ear
vestibular system cochlea: snail, organ of corti
33
describe the structure of the cochlea
sprial from base to apex in the snail shell Scala vestibuli: continuous to the vestibule, oval window scala media: basilar membrane, hearing hair cells scala tympani: to round window (tympanic cavity) unidirectional flow of perilymph
34
describe hair cell hearing receptors
cannot regenerate like rods and cones body = basilar membrane cilia = exposed in endolymph
35
describe the hair cells in the endolymph
multiple stereocilia: bound together through tip link no kinocilium
36
arrangement of hair cells for inner and outer regions
1 line of inner cells: auditory function 3 lines of outer hair cells: modulatory function; changing shape and size
37
describe the path of signal transduction of sound wave stimuli
1. Stapes pushed flow of perilymph with sound wave 2. expansion of scala vestibuli/typani and relative movement of tectorial and basilar membrane 3. sound wave stops and reverses process 4. cilia displacement changes 5. displacement causes different neurotransmitter release
38
describe how cilia movement affects neurotransmitter release/depolarization
stereocilia tilt to taller ones = increase depolarization stereocilia tilt away from taller ones = decrease depolarization **graded potenital, no AP by hair cells, not neurons** above actions result in membrane potential change in cochlear nerve endings
39
shape of basilar membrane
increased width and flexibility from base to apex
40
decsribe frequency tuning of the ear
tonotopy is maintained all the way to A1 wave travels along basilar membrane maximal displacement matches frequency - base (more outward) for high frequency - apex (deeper in ear) for low natural sound is a spectrum of frequencies and must be decomposed
41
conscious perception of sounds needs how many neurons and where are they
needs 4 neurons 1st = spiral ganglion 2nd = cochlear nuclei 3rd = inferior colliculus 4th = MGN of thalamus
42
where in the brain is sound/tonotopy perceived
primary auditory cortex (Brodmann area 41) from lateral to medial = low to high frequency anterior to posterior = detect where sound is coming from
43
why do we need 2 ears for hearing
localization of sound brain computes difference between ears to determine location of sound owls have 2 ears on 2 different levels to increase difference in sounds and provide more accurate localization
44
what is interaural time difference
in ears, one side needs longer time to detect the sound wave used for detection of low frequency sounds: far away along basilar membrane to the apex
45
what is interaural intensity difference
your head will block or absorb sound sound waves higher frequency sounds = higher energy
46
location of vestibular system
posterior to bony labyrinth 30 deg elevated anteriorly when looking forward
47
components of the vestibular system
saccule and utricle = otolith organs; each contains a maculae in endolymph (what measures the angular motion) horizontal/anterior/posterior canals = semicircular canals, cupula acts as barrier at end of canal and deforms based on flow of endolymph
48
receptors for the vestibular system
hair cells only cilia exposed in the endolymph multiple stereocilia with 1 kinocilium: stereocilia tilt to kinocilium which increases depolarization
49
what is the maculae
cilia of hair cells are covered by a layer of CaCO3 crystals (otoconia) in the saccule and utricle Part that detects angular motion
50
what is BPPV
benign paroxysmal positional vertigo, dislodge of otoconia into semicircular canals
51
how are hair cells aligns in the maculae
opposite along striola in maculae arrows to the kinocilium
52
macula in saccule vs utricle
saccule = vertical alignment, vertical and A/P displacement utricle = horizontal and anterior tilted up 30 degrees, A/P and side/side displacement **need to consider bilateral opposite alignment and coordinated functions
53
functions of the maculae
detect static and linear acceleration constantly activated or inhibited
54
describe the structure of the semicircular canal
all located laterally one end open and the other blocked by ampulla cell body embedded in crista cilia in cupula of endolymph
55
how do the anterior, posterior, and horizontal canals lie in the inner ear
contralateral anterior and posterior canals are in the same plane; 45 degrees to sagittal plane bilateral horizontal canals in the same plane
56
functions of the semicircular canals
detect angular acceleration or deceleration dynamic activation or inhibition
57
what is a unique characteristic of hair cells
basal discharge rate
58
direction of kinocilia in bilateral horizontal canals and bilateral anterior/posterior canals
kinocilia in horizintal canals = utricle kinocilia in anterior/posterior canals = face away from the utricle
59
how does endolymph flow with head RT
inertia makeds endolymph flow to opposite direction
60
when you rotate your head from side to side in the transverse plane, what canals are inhibited and activated
activate ipsilateral horizontal canals but inhibits contralateral horizontal canals
61
when you rotate your head downward/forward to right or left, what canals are activated
activating anterior and contralateral posterior canals
62
effects/benefits of epely maneuver
decreased 2/3 of falls in community dwelling geriatric population
63
where does the vestibular pathway project to in the neocortex
no primary cortex multiple regions mainly in parietal lobe
64
descrribe the neuronal pathway of the vestibular system
1st order = scarpas ganglion 2nd order = vestibular nuclei (superior/inferior, lateral/medial) 3rd order = B VPM of thalamus; integrates with proprioception from other body parts in VPL
65
purpose of VOR
vision stabilization
66
what canals are activated/inhibited in VOR
turning head activates ipsilateral canal and inhibits the contralateral one
67
VOR signal is conducted where and what happens then
conducted to medial vestibular nucleus activates contralateral CN VI nucleus - this activates the contralateral lateral rectus - also activates contralateral CN III nucleus, then contralateral medial rectus will be activated inhibits ipsilateral CN VI nucleus - inhibits ipsilateral lateral rectus and contralateral medial rectus results = turning head side to side, both eyes rotate oppositely to fix on the target
68
what tract does VOR signals travel on
medial longitudinal fasciculus, ascending limb
69
what is the vestibulocervical/vestibulospinal reflex (VCR/VSR)
for posture control integrated vestibular and proprioceptive signals by cerebellum
70
how do signals from VSR/VCR travel
input to lateral vestibular nucleus - via lateral vestibular spinal tract; ipsilateral proximal extremity muscleds input to medial vestibular nucleus - via medial vestibulospinal tract; bilateral trunk, mainly neck and upper body all tracts of axons via medial longitudinal fasciculus, descending limb
71
list the nuclei in the rostral medulla oblongata
ss: spinal tract of trigeminal n sm: nucleus ambiguus (vm and sm for IX/X) vs: solitary nucleus, taste of visceral sensation of organs vm: inferior salivatory nucleus for IX, dorsal vagus nuclues/nucleus ambiguus for X
72
what CNs share spinal trigeminal nuclei for ss
VII, IX, X
73
ss to external ear
CN VII, IX, X
74
ss to posterior 1/3 tongue
CN IX
75
ss to pharynx and larynx
CN X
76
somatic motor functions of CN IX and X
via bilateral corticobulbar control CN IX: stylopharyngeus CN X: levator veli palantini, styloglossus/palatoglossus, and all other pharyngeal and laryngeal muscles damage = dysphagia and dysarthria
77
visceral sensory functions of IX and X
visceral sensory detects internal chemical stimuli, independent or can follow visceral motor CN IX - lesser petrosal n: otic ganglion- parotid gland - carotid sinus/body: baroreceptors (mechanical) and SaO2 (chemical) CN X - aortic arch: baroreceptors - internal organs until end of midgut
78
describe the peripheral parasympathetic nervous system stemming from the brain (CN, ganglion, and target structures)
CN III - ciliary ganglion - ciliary body and pupillary sphincter CN VII - pterygopalantine ganglion = lacrimal/sinus mucosal gland - submandibular ganglion = submandibular and sublingual salivary gland CN IX - Otic ganglion - parotid salivary gland CN X - ganglia in target organs - visceral organs until end of midgut
79
parasympathetic innervation from sacrum CN
pelvic splanchnic n ganglia in target organs hindgut and pelvic visceral organs
80
describe the nuclei/path of CN XI: spinal accessory
nuclei in upper cervical SC: bilateral corticobulbar innervation - all from C1-C5: rootlet from medulla runs to CN X - lateral SC, not from ventral rami crosses jugualr foramen with CN IX and CN X
81
somatic motor function of CN XI
SCM innervation - torticollis = ipsilateral SB and contralateral RT; can be due to ipsilateral tightness or contralateral weakness- muscle balance problem trapezius innervation
82
describe the nuclei for CN XII and its innervation
nuclei in proximal medulla: contralateral corticobulbar innervation UMN injury = no obvious atrophy LMN injury = obvious atrophy
83
path of hypoglossal n
Exit medulla at anterolateral sulcus between pyramid and olive crosses the hypoglossal canal
84
function/type of innervation for CN XII
only somatic motor- intrinsic and extrinsic tongue muscles damage = protrusion of tongue push to affected/weak side- muscle imbalance acts as a shuttle for C1 ventral root - ansa cervicalis sup root - C1 to thyrohyoid muscle - C1 to geniohyoid muscle
85

Year 2: NeuroBiology (10 decks)

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