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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
Q

what pierces the buccinator

A

parotid gland duct

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26
Q

where do the dorsal and ventral nuclei components of the facial somatic motor nucleus receive projections from and what areas do they control respectively

A

dorsal nucleus: projections from bilateral anterior cingulate cortex (ACC), forhead and scalp

ventral nucleus: projections from contralateral cerebral cortex except ACC, lower face

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27
Q

describe how S&S would be different between a LMN injury of CN VII vs UMN injury

A

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

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28
Q

purpose of the external ear

A

collect and conduct sound waves through air

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29
Q

function of middle ear

A

turn sound waves to vibration (both are mechanical waves)

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30
Q

what does the middle ear include

A

tympanic cavity: tympanic membrane

ossicles: malleus, incus, stapes

muscles: tensor tympani (CNV), stapedius (CN VII); function to decrease vibration

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31
Q

what is hyperacusis

A

caused by functional loss of muscles of middle ear

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32
Q

what makes up the inner ear

A

vestibular system

cochlea: snail, organ of corti

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33
Q

describe the structure of the cochlea

A

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

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34
Q

describe hair cell hearing receptors

A

cannot regenerate like rods and cones

body = basilar membrane

cilia = exposed in endolymph

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35
Q

describe the hair cells in the endolymph

A

multiple stereocilia: bound together through tip link

no kinocilium

36
Q

arrangement of hair cells for inner and outer regions

A

1 line of inner cells: auditory function

3 lines of outer hair cells: modulatory function; changing shape and size

37
Q

describe the path of signal transduction of sound wave stimuli

A
  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
Q

describe how cilia movement affects neurotransmitter release/depolarization

A

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
Q

shape of basilar membrane

A

increased width and flexibility from base to apex

40
Q

decsribe frequency tuning of the ear

A

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
Q

conscious perception of sounds needs how many neurons and where are they

A

needs 4 neurons

1st = spiral ganglion
2nd = cochlear nuclei
3rd = inferior colliculus
4th = MGN of thalamus

42
Q

where in the brain is sound/tonotopy perceived

A

primary auditory cortex (Brodmann area 41)

from lateral to medial = low to high frequency

anterior to posterior = detect where sound is coming from

43
Q

why do we need 2 ears for hearing

A

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
Q

what is interaural time difference

A

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
Q

what is interaural intensity difference

A

your head will block or absorb sound sound waves

higher frequency sounds = higher energy

46
Q

location of vestibular system

A

posterior to bony labyrinth

30 deg elevated anteriorly when looking forward

47
Q

components of the vestibular system

A

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
Q

receptors for the vestibular system

A

hair cells

only cilia exposed in the endolymph

multiple stereocilia with 1 kinocilium: stereocilia tilt to kinocilium which increases depolarization

49
Q

what is the maculae

A

cilia of hair cells are covered by a layer of CaCO3 crystals (otoconia) in the saccule and utricle

Part that detects angular motion

50
Q

what is BPPV

A

benign paroxysmal positional vertigo, dislodge of otoconia into semicircular canals

51
Q

how are hair cells aligns in the maculae

A

opposite along striola in maculae

arrows to the kinocilium

52
Q

macula in saccule vs utricle

A

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
Q

functions of the maculae

A

detect static and linear acceleration

constantly activated or inhibited

54
Q

describe the structure of the semicircular canal

A

all located laterally

one end open and the other blocked by ampulla

cell body embedded in crista

cilia in cupula of endolymph

55
Q

how do the anterior, posterior, and horizontal canals lie in the inner ear

A

contralateral anterior and posterior canals are in the same plane; 45 degrees to sagittal plane

bilateral horizontal canals in the same plane

56
Q

functions of the semicircular canals

A

detect angular acceleration or deceleration

dynamic activation or inhibition

57
Q

what is a unique characteristic of hair cells

A

basal discharge rate

58
Q

direction of kinocilia in bilateral horizontal canals and bilateral anterior/posterior canals

A

kinocilia in horizintal canals = utricle

kinocilia in anterior/posterior canals = face away from the utricle

59
Q

how does endolymph flow with head RT

A

inertia makeds endolymph flow to opposite direction

60
Q

when you rotate your head from side to side in the transverse plane, what canals are inhibited and activated

A

activate ipsilateral horizontal canals but inhibits contralateral horizontal canals

61
Q

when you rotate your head downward/forward to right or left, what canals are activated

A

activating anterior and contralateral posterior canals

62
Q

effects/benefits of epely maneuver

A

decreased 2/3 of falls in community dwelling geriatric population

63
Q

where does the vestibular pathway project to in the neocortex

A

no primary cortex

multiple regions mainly in parietal lobe

64
Q

descrribe the neuronal pathway of the vestibular system

A

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
Q

purpose of VOR

A

vision stabilization

66
Q

what canals are activated/inhibited in VOR

A

turning head activates ipsilateral canal and inhibits the contralateral one

67
Q

VOR signal is conducted where and what happens then

A

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
Q

what tract does VOR signals travel on

A

medial longitudinal fasciculus, ascending limb

69
Q

what is the vestibulocervical/vestibulospinal reflex (VCR/VSR)

A

for posture control

integrated vestibular and proprioceptive signals by cerebellum

70
Q

how do signals from VSR/VCR travel

A

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
Q

list the nuclei in the rostral medulla oblongata

A

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
Q

what CNs share spinal trigeminal nuclei for ss

A

VII, IX, X

73
Q

ss to external ear

A

CN VII, IX, X

74
Q

ss to posterior 1/3 tongue

A

CN IX

75
Q

ss to pharynx and larynx

A

CN X

76
Q

somatic motor functions of CN IX and X

A

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
Q

visceral sensory functions of IX and X

A

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
Q

describe the peripheral parasympathetic nervous system stemming from the brain (CN, ganglion, and target structures)

A

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
Q

parasympathetic innervation from sacrum CN

A

pelvic splanchnic n

ganglia in target organs

hindgut and pelvic visceral organs

80
Q

describe the nuclei/path of CN XI: spinal accessory

A

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
Q

somatic motor function of CN XI

A

SCM innervation
- torticollis = ipsilateral SB and contralateral RT; can be due to ipsilateral tightness or contralateral weakness- muscle balance problem

trapezius innervation

82
Q

describe the nuclei for CN XII and its innervation

A

nuclei in proximal medulla: contralateral corticobulbar innervation

UMN injury = no obvious atrophy

LMN injury = obvious atrophy

83
Q

path of hypoglossal n

A

Exit medulla at anterolateral sulcus between pyramid and olive

crosses the hypoglossal canal

84
Q

function/type of innervation for CN XII

A

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
Q
A

Year 2: NeuroBiology (10 decks)

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