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Y2 LCRS Neuroscience and Mental Health > auditory function and balance > Flashcards

auditory function and balance Flashcards

vestibular system: identify the functions and list the types of signals derived from the vestibular system

1
Q

input into brain from a) eye b) (inner) ear c) foot

A

a) visual b) rotation, movement and gravity c) pressure

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2
Q

outputs from brain based on inuputs

A

ocular reflex, postural control, nausea

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3
Q

type 1 hair cell in transduction: number, afferent and efferent, shape

A

more in number, direct afferent, indirect efferent, round (similar to inner in hearing)

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4
Q

type 2 hair cell in transduction: number, afferent and efferent, shape

A

fewer in number, direct afferents and efferents, long and thin (similar to outer in hearing)

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5
Q

location of hair cells in Otolith organs (utricle and saccule), and displacement plane and liquid location

A

utricule (hair cells inferior - linear displacement, liquid on top), saccule (hair cells unilateral - vertical displacement, liquid elsewhere)

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6
Q

static labyrinth: structures in otolith organs, and what are otoliths

A

maculae (have hair cells), hair cells, gelatinous matrix (on top of hair), otoliths (carbonate crystals)

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7
Q

static labyrinth: where is striola and impact upon hair bundle movement

A

central part of maculae, where on left and right there are opposing hair bundle polarities as orientated in separate dirctions (symmetrical), so any movement in any direction stimulates a distinct subset of cells (excitation one side and inhibition other side); movement causes Ca2+ influx and release of neurotransmitter to nerve

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8
Q

kinetic labyrinth: semicircular canals

A

hair cells only in ampulla (crista); less dense gelatinous matrix (cupula) vs otolith organs; kinocilia (same direction on each side of head, so no striola section and symmetry; instead entire cell is in opposite direction, gaining symmetry this way and allowing excitation and inhibition); anterior canal (45 degrees front), posterior canal (45 degrees back), lateral canal (30 degrees)

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9
Q

blood supply of vestibular system

A

some shared with brain as well as ear: anterior inferior cerebellar artery from basilar artery branches to inner ear and cerebellum, so stroke with inner ear symptoms but actually in anterior inferior cerebellar artery (brain stroke)

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10
Q

6 normal functions of vestibular system

A

subserve perception of movement in space and tilt with respect to gravity.
provide reflex balance reactions to sudden instability of gait or posture ‘vestibulo-spinal reflexes’; stabilise eyes on earth fixed targets preserving visual acuity during head movements ‘vestibular-ocular reflexes’; assist control of blood pressure and heart rate during rapid up-down tilts; assist synchronisation of respiration with body reorientations; provokes motion sickness when stimulated in unusual motion environments; provide reference of absolute motion in space, helping interpret relativistic signals of other senses in creating a perception of spatial orientation

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11
Q

what does hair cell synapse with

A

primary neurone dendrite (cell body in Scarpas ganglion)

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12
Q

what does primary neurone project to

A

vestibular nuclei in brainstem

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13
Q

what stimulates hair cell

A

deflection by forces of intertial resistance to acceleration (gravity for otoliths) and endolymphatic fluid rotation (canals)

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14
Q

hair cell receptor potential: which directions cause depolarisation and hyperpolarisation

A

depolarisation caused by deflection towards kinocilium; hyperpolarisation caused by deflection away from kinocilium

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15
Q

ganglion cell discharge: which directions increase and decrease firing frequency

A

increased firing frequency towards kinocilium; decreased firing frequency away from kinocilium

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16
Q

2 locations where primary afferents of vestibular nerves end

A

in vestibular nuclei and in cerebellum

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17
Q

4 vestibular nuclei

A

superior, lateral, medial, inferior

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18
Q

organisation of static labyrinth

A

otoliths in lateral and inferior vestibular nuclei

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19
Q

organisation of kinetic labyrinth

A

superior and medial vestibular nuclei

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20
Q

diagram of vestibular nuclei in dorsal view

A

slide 18

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21
Q

4 locations where vestibular nuclei project

A

spinal cord, nuclei of extraocular muscles, cerebellum, ANS centres for cardiovascular and respiratory control

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22
Q

diagram of vestibular pathways

A

slide 19

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23
Q

where do vestibular nuclei receive input from

A

hair cells in semicircular canals or otolith organs via vestibular nerve

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24
Q

superior and lateral vestibular nuclei pathway

A

medial lemniscus to ventroposterior nuclei -> internal capsule to vestibular cortex (superior temporal gyrus, posterior to primary motor cortex)

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25
Q

lateral, medial and inferior vestibular nuclei: 3 pathways for reflex

A

vestibulospinal reflex, vestibulo-ocular reflex, vestibulocerebellar reflex

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26
Q

vestibulospinal reflex: via what and to where

A

lateral vestibulospinal tract to limb and trunk; medial vestibulospinal tract to upper back and neck

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27
Q

vestibulo-ocular reflex: via what and to where

A

medial longitudinal fasciculus to oculomotor nucleus (oculomotor nerve -> superior, medial and inferior rectus), abducens nucleus (abducens nerve -> lateral rectus), trochlear nucleus (trochlear nerve -> superior oblique)

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28
Q

vestibulocerebellar reflex: via what and to where

A

inferior cerebellar peduncle to vestibulo-cerebellum (flocculonodular lobe)

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29
Q

3 functions of vestibulocerebellar pathways

A

movement coordination, posture regulation, VOR modulation

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30
Q

what region of the diencephalon do some vestibular nuclei project to

A

thalamus

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31
Q

where do thalamic nuclei project to

A

head region of primary somatosensory cortex and superior parietal cortex

32
Q

what is vestibular cortex (superior parietal cortex) concerned with

A

spatial orientation

33
Q

what might cortical projections account for

A

dizziness (vertigo) during certain kinds of vestibular testing

34
Q

2 regions of vestibular cortex where thalamic nuclei project to

A

PIVC (parieto-insular vestibular cortex) and PIC (posterior insular cortex)

35
Q

2 sections of cerebellum

A

vermis, flocconodular lobe (most inferior)

36
Q

2 functions of vestibulocerebellum

A

maintenance of balance, control eye movements

37
Q

2 functions of spinocerebellum

A

regulation of muscle tone, coordination of skilled voluntary movement

38
Q

function of cerebrocerebellum

A

planning of voluntary activity

39
Q

3 sensory inputs of cerebellum

A

visual, vestibular, proprioceptive

40
Q

2 central processing of input in cerebellum

A

primary processor (vestibular nuclear complex), adaptive processor (cerebellum)

41
Q

2 motor outputs of primary processor (vestibular nuclear complex)

A

motor neurones for eye movements or positional movements

42
Q

3 functions of vestibular system

A

detect and inform about head movements, keep images fixed in retina during head movements, postural control

43
Q

why does each canal have a resting discharge (tonic firing rate)

A

always have stimuli inside ear (e.g. gravity), so still have some discharge from hair cells to nerve (increases during excitation, decreases during inhibition); when head is still, tonuses from right and left canals balance out

44
Q

otolith organs: what causes movement of hair bundles

A

linear acceleration (utricle), tilt and vertical acceleration (saccule); stimulated by inertial resistance of otoconial mass to linear head acceleration (tends to stay still when head moves); omni-directional

45
Q

otolith organs: effect of movement

A

depolarisation (excitation) or hyperpolarisation (inhibition) of nerves, with vector sum of utricular and saccular stimulation patterns providing signal of linear acceleration in all 3D directions

46
Q

otolith organs: movement of utricule

A

horizontal (hair cells project vertically with directional sensitivities in all combinations of lateral and anteroposterior directions)

47
Q

otolith organs: movement of saccule

A

vertical (hair cells with their overlaying layer of otoconia project normal to the plane with directional sensitivities in all combinations of vertical and anteroposterior directions)

48
Q

semi-circular canals: response to angular acceleration

A

endolymph flow in opposite direction to head motion, pushing against cupula

49
Q

response to acceleration vs velocity

A

inertia at constant velocity so no cupula movement

50
Q

semi-circular canal pairing

A

one side stimulated and other inhibited by same movement as in same plane: both horizontal (lateral), left anterior paired with right posterior, right anterior paired with left posterior

51
Q

how are semi-circular canals unidirectionally orientated

A

hair cells project from ampulla in wall of canal and are unidirectionally oriented, so that acceleration phase of head rotation to a particular side or direction preferentially stimulates canals on that side e.g. rotation to right stimulates right canal, and rotation in opposite direction inhibits canal activity

52
Q

what happens to semi-circular canals when head rotation decelerates to stop (ie acceleration in the opposite direction)

A

canal on opposite side is stimulated e.g. stopping rightwards rotation stimulates left canal

53
Q

2 vestibular reflexes

A

vestibulo-spinal reflex, vestibuo-ocular reflex

54
Q

2 vestibulo-spinal reflex pathways

A

lateral vestibulo-spinal tract, medial vestibulo-spinal tract

55
Q

lateral vestibulo-spinal tract: side and innervation to

A

ipsilateral, motor neurones to limb muscles

56
Q

medial vestibulo-spinal tract: side and innervation to

A

bilateral, motor neurones to neck and back muscles

57
Q

diagram of 2 vestibulo-spinal reflex pathways

A

slide 39

58
Q

lateral vestibulo-spinal tract pathway

A

12:00 slide 40

59
Q

lateral vestibulo-spinal tract pathway

A

MORE

60
Q

medial vestibulo-spinal tract pathway

A

slide 41

61
Q

medial vestibulo-spinal tract pathway

A

MORE

62
Q

function of vestibuo-ocular reflex

A

keep images fixed while head is moving

63
Q

vestibuo-ocular reflex: what 2 nuclei does it connect

A

vestibular nuclei and oculomotor nuclei

64
Q

vestibuo-ocular reflex: latency

A

5-7ms (very fast) so don’t realise it is happening (reflex)

65
Q

vestibuo-ocular reflex: eye and head movement relation

A

eye movement in opposite direction to head movement

66
Q

structure of eye

A

slide 43

67
Q

vestibulo-ocular pathways

A

slide 44

68
Q

vestibulo-ocular pathways

A

info from oculomotor (III) and abducens (VI) for medial and lateral; excitation and inhibition

69
Q

vestibulo-ocular pathways

A

slide 45

70
Q

horizontal vestibulo-ocular pathway

A

slide 46

71
Q

horizontal vestibulo-ocular pathway

A

MORE

72
Q

vertical vestibulo-ocular pathway (anterior)

A

slide 47

73
Q

vertical vestibulo-ocular pathway (anterior)

A

one side stimulates one side and inhibits other

74
Q

vertical vestibulo-ocular pathway (posterior)

A

slide 48

75
Q

vertical vestibulo-ocular pathway (posterior)

A

MORE

76
Q

effect of loss of canal function on one side

A

gives a permanent partial impairment of sensitivity to rotation in the’ on’ direction of the defunct canal

77
Q

effect of loss of otolith function on one side

A

no effect as omni-directional (all directions)

Y2 LCRS Neuroscience and Mental Health (79 decks)

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