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ANAT + PHYS (9610) > UNIT 7: CN VIII + Development > Flashcards

UNIT 7: CN VIII + Development Flashcards

1
Q

structures of the face and neck in the human embryo are derived from a series of

A

arches, clefts, pouches

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2
Q

arches and clefts arise …

A

externally at the anterior end of the embryo around the upper end of the foregut - primitive pharynx

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3
Q

pouches arise …

A

internally, are the “internal partners” of the external clefts

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4
Q

pharyngeal clefts are

A

slit like depressions bw the pharyngeal arches

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5
Q

1st cleft is the _______ and deepens to form…

A

hyomandibular cleft

deepens to form the external auditory meatus of the ear and external surface of the TM

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6
Q

2nd to 4th clefts are …

A

obliterated by rapid dev of tissue of the 2nd arch

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7
Q

if obliteration of the 2nd to 4th clefts are incomplete then…

A

a cervical cyst (space) may persist deep to the skin in the neck region

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8
Q

during 5th week 6 _____ of tissue develop on both sides of the ….

A

hillocks aka mounds

1st cleft

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9
Q

subsequent dev of the hillocks on either side of the 1st cleft leads to

A

formation of the auricle

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10
Q

external auditory meatus is formed from the

A

deepening of the 1st pharyngeal cleft

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11
Q

TM arises at

A

junction of 1st pharyngeal cleft and pouch

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12
Q

pharyngeal pouches are

A

pockets w/i the primitive pharynx (medial surface) that correspond to the pharyngeal clefts

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13
Q

in lower vertebrates, pharyngeal clefts and pouches are

A

open to each other to form gill slits

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14
Q

in human tissues …. tissue bw the 1st cleft and 1st pouch forms…

A

the TM … the remaining clefts are obliterated

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15
Q

distal end of the 1st pharyngeal pouch enlarges to form the

A

TC

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16
Q

distal end of 1st pharyngeal pouch that enlarges to form the TC, expands to enclose and surround…

A

the dev ossicles (from 1st and 2nd arches)

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17
Q

further posterior expansion of the TC gives rise to

A

the aditus (leads to mastoid antrum and air cells)

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18
Q

1st pharyngeal pouch continues to elongates and….

A

maintains opening into the pharynx, forming the eustachian tube

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19
Q

lining at the distal end of the 1st pharyngeal pouch forms the ….

A

internal layer of the TM

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20
Q

thickening of surface ectoderm at week 4 is recognized as the

A

otic placode

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21
Q

otic placode deepends into the ____ and eventually becomes _____ from surface ectoderm as the _____

A

otic pit
cut off
otic vesicle

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22
Q

otic vesicle gives rise to

A

membranous labyrinth

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23
Q

otic vesicle looks like an …. diverticulum forms….

A

inverted pear w small diverticulum

diverticulum forms the endolymphatic duct and sac

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24
Q

wider part of the otic vesicle gives rise to 3 …

A

flattened sacs … semicircular ducts

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25
Q

narrow ends of otic vesicle elongate and begin to ….

A

coil to form the cochlear duct

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26
Q

on the otic vesicle the utricle and saccule form bw

A

semicircular and cochlear ducts

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27
Q

auricular tags are

A

residual material along fusion line of 1st branchial arch; anterior to auricle

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28
Q

atresia

A

congenital absence of EAM

tympanic cavity may also be absent

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29
Q

microtia

A

small pinna; underdeveloped features

may still have an EAM

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30
Q

CN VIII is classified as a

A

special sensory nerve

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31
Q

end receptors in both systems of CN VIII are…

A

hair cells

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32
Q

dendrites of primary sensory neurones extend a very short distance in CN VIII from _____ to nerve cell bodies

A

bases of HCs

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33
Q

vestibular system’s of CN VIII ganglion is…

A

vestibular ganglion (only one! hence ganglion)

34
Q

auditory sys of CN VIII has its ganglia in

A

spiral ganglia (many of them hence ganglia)

35
Q

steps of hearing… (include what happens if sound it too loud)

A

Sound funneled by pinna to EAM which amplifies sound and now that acoustic energy is hitting the ear drum

Sound waves make TM move and vibrate which vibrates the malleus which then vibrates the incus and then the stapes

If the sound is too loud the tensor tympani would contract to dampen the vibration of the TM and if we rly need to do it more stapedius will pull on stapes and stop transmission

Stapes footplate pumps on fluid filled sys via the oval window, sets up travelling wave, high freq sounds pumping fast, low freq pumping slow, will move the perilymph … which bends the basilar membrane close to the base of the cochlea, the outer hair cells that are imbedded in the tectorial membrane this makes the endolymph move, then this makes the stereocilia in the IHCs move which makes up register sound

36
Q

axons of primary neurons in CN VII travel through the …

A

IAM with CN VII

37
Q

after primary neurons travel thru IAM, it enters the _____ at its junction with the pons and terminates in ___ vestibular nuclei and ___ cochlear nuclei

A

medulla
brainstem nuclei
4
2

38
Q

name the 4 vestibular nuclei

A

superior
medial
lateral
inferior

39
Q

name 2 cochlear nuclei

A

dorsal
ventral

40
Q

input predominantly from the semicircular ducts goes to what nuclei…. and to coordinate what?

A

superior nucleus = to coordinate eye movements

medial nucleus = to coordinate postural head and neck movements

41
Q

input predominantly from maculae goes to what nuclei.. to coordinate what?

A

lateral nucleus = to coordinate postural responses to gravity

inferior nucleus = projects to vestibular regions of cerebellum and other vestibular nuclei

42
Q

all vestibular sub nuclei send a few secondary nerves to the ____ and a tertiary nerve to the _____…. this allows for ….

A

thalamus
somatosensory cortex

conscious appreciation of balance and head position

43
Q

auditory NS is complex, involves two ascending systems called ____ and ____, and two descending systems called _____ and ____

A

classical
non-classical

corticofugal
olivocochlear

44
Q

classical ascending auditory sys is….

A

tonotopic system; distinct freq tuning, neurons are organized anatomically according to freq to which they are tuned

45
Q

non-classical auditory sys …

A

project to secondary auditory cortices

46
Q

3 main nuclei of the classical ascending sys….. explain pathway

A

cochlear nuclei = dorsal and ventral nuclei in medulla

central nucleus of inferior colliculus in midbrain

medial geniculate body in thalamus

Synapse point at these nuclei
First one from the ear is the cochlear nuclei
Next one is in the midbrain
Then it synapses in the thalamus (medial geniculate body is part of the auditory pathway)
Then it goes to the primary auditory cortex

47
Q

there are also 2 additional nuclei in the classical ascending pathway that have some synaptic connections… … what do they help w?

Not all fibres stop at SOC (which is next door to the cochlear nuclei) and not all stop at nuclei of the LL

Option stops begin sound localization (means we don’t have to wait for it to go to cortex for sound localization… ex. May not know which emergency vehicle is making a siren but we just need to be on alert, don’t need cortex for that, aka don’t need to know which emergency vehicle it is)

A

superior olivary complex

nuclei of the lateral lemniscus

48
Q

classical ascending pathway contains connections bw the 2 sides of the… which is important for…

A

CNS at several levels in the ascending pathway - very important for directional hearing

49
Q

how is the cochlea/heschel’s gyrus like a piano

A

High tones at base

Low tones at apex

Tonotopic organization

We don’t loose this detail

We keep it – and at heschel’s gyrus is also layed out by freq

Freq info given to cortex as is

The cochlea told us info about sound signal, but maintains that so the cortex doesnt have to do that again

50
Q

in the auditory nerve, cell bodies of the primary sensory neuron are w/i the… in the…

A

spiral ganglia in the modiolus of the cochlea

51
Q

all hair cells have both ____ and ____ innervation, but majority are ____

A

afferent and efferent
afferent

52
Q

auditory nerve has type __ and ___ afferent nerve fibres…. _______ fibres in humans

A

type I and II

30,000

53
Q

type I afferent nerve fibres are from ____, What ratio

A

IHCs
1 HC to many nerves

54
Q

type II afferent fibres are from ____, ratio is…

A

OHCs
many hair cells to 1 nerve

55
Q

type I fibres lead from IHCs to cells in the _______ nuclei

A

cochlear

56
Q

type I fibres from IHCs is the pathway by which all …

A

auditory info is transmitted from the organ of corti to higher centres of the auditory CNS

57
Q

for type I fibres, diameters are relatively _____; limits differences in ….

A

homogenous

limits diffs in conduction velocity across fibres leading to high degree of temporal coherence

58
Q

homogeniety of type I fibres is important for

A

discrimination of complex sounds (speech) - and timing

variation in fibre size (and thus conduction velocity) inc w age, may explain some hearing probs not directly related to elevation of pure tone threshold

59
Q

type II fibres innervate… what percentage of fibres are type II… where do they project…. function?

A

OHCs
1-5%

they project mostly to the dorsal cochlear nucleus (DCN); function is relatively unknown

60
Q

one to many innervation =

A

type II fibres

61
Q

many to one innervation =

A

type I fibres

62
Q

cochlear nerve fibres terminate in the

A

ipsilateral cochlear nuclei

63
Q

from the dorsal cochlear nuclei, the cochlear nerve mainly projects to …

A

the contralateral inferior colliculus by way of the lateral lemniscus

64
Q

some cochlear nerve fibres travel to…. why?

A

facial motor nucleus and trigeminal motor nucleus

acoustic reflex and ossicular chain dampening

65
Q

cochlear nuclei from left and right sides of the brainstem are _____ - most ____ connection

A

connected
peripheral

66
Q

cochlear nuclei from L and R sides being connected allows for …..

A

bilateral pathways ensure redundancy of auditory info in the event of disease or damage

67
Q

superior olivary complex is a ______ in the _____, where….

A

nucelus in medulla

only some fibres of the cochlear nerve synapse in this medullary nucleus before forming the LL

68
Q

superior olivary complex receives bilateral input from _____ : it is the first group of neurons to… how?

A

cochlear nuclei

first group of neurons to integrate info from both ears; involved in directional hearing

compares arrival time of neural activity from 2 ears

compares intensity diffs from 2 ears

69
Q

nuclei of SOC comprise some of the most…

A

complicated parts of the ascending pathways; largest inter-species variation

70
Q

inferior colliculus …

A

a midbrain relay nucleus, where all ascending auditory info is channeled

caudal to superior colliculus

71
Q

Lateral lemniscus fibres synpase in the

A

inferior colliculus

72
Q

left IC and right IC are ….

A

connected - important communication for directional hearing based on diffs in sound intensity bw the 2 ears

73
Q

medial geniculate body …

A

thalamic auditory relay nucleus

all fibres from the ICC are interrupted by the MGB

no connections bw left and right MGB

74
Q

how is the non-classical ascending pathway diff from the classical

A

its a diffuse sys

not as clearly organized anatomically

receives input from other sensory systems

75
Q

in non-classical pathway, the inferior colliculus synapses w the …. why?

A

superior colliculus

to coordinate eye movements and other motor responses to auditory stimuli that are important for directional hearing

76
Q

neurons in non-classical ascending pathway respond to both… how is it diff to classical?

A

sound and other sensory stimuli such as touch and light

neurons in classical auditory pathway, up to and including the AI cortex, respond to sound stimulation

77
Q

descending fibres are ____ abundant as ascending fibres, but…

A

abundant
much less is known about them

78
Q

corticofugal descending pathway central part originates from

A

auditory cerebral cortex

79
Q

olivocochlear descending pathway is from the ____ and ____ to _____ and ____

A

auditory cortex and SOC
to cochlear nuclei and cochlea

80
Q

olivocochlear is a _____ auditory pathway, influences ability of ….

A

efferent
OHCs to amplify the motion of the basilar membrane

81
Q

3 ways to test CN VIII

A

pure tone audiometry = detection of various sound freq

otoacoustic emissions = sounds produced by inner ear (spontaneous vs evoked)

evoked auditory brainstem responses = evoked potentials recorded in response to sounds

ANAT + PHYS (9610) (21 decks)

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