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Neurology > Sensory Transduction > Flashcards

Sensory Transduction Flashcards

1
Q

What is the role of the hair cell?

A

Transduces the stimulus

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2
Q

What are the cilia responsible for?

A

Stimulus responsive cation entry = cell body releases glutamate onto efferent nerve endings

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3
Q

What regulates the response of cilia to a stimulus?

A

Afferent nerves

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4
Q

What are the tip links of hair cells?

A

Specialised structures that gate or close the TMCl channel mouth depending on cilial tilt

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5
Q

What does the tonic release of glutamate from cilia allow?

A

Modulation of AP frequency

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6
Q

What is sound?

A

Repetitive variation in a medium (e.g air)

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7
Q

How does sound travel?

A

Object vibrates which produces changes in air pressure = air vibrates and travels in three dimensions

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8
Q

What effect does sound have on the ear?

A

Sound vibrates the eardrum and ossicles = this vibration spreads to the cochlea where it is converted to vibration of fluids

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9
Q

What captures vibration in the cochlea?

A

Hair cells = physical vibration is transduced to neural energy

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10
Q

What are the three mechanisms for impedance matching in the middle ear?

A

Area ratio of ear drum to stapes footplate = 20:1
Lever action of ossicles
Bucking of ear drum

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11
Q

What does the inner ear contain?

A

3 fluid filled cavities

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12
Q

What does Reissner’s membrane separate?

A

Scala vestibuli and scala media

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13
Q

What does the basilar membrane separate?

A

Scala media and scala tympani

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14
Q

Where is the scala media closed off?

A

At the apex

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15
Q

Where are the scala tympani and scala vestibuli connected?

A

At the helioctrema

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16
Q

What structures are in contact with the oval window and round window?

A

Oval window = scala tympani

Round window = scala vestibuli

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17
Q

Where are hair cells located in the organ of Corti?

A

Between the basilar membrane and reticular lamina

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18
Q

Where are the tips of the stereocilia of the organ of Corti located?

A

The tectorial membrane

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19
Q

Where in the inner ear is the perilymph continuous?

A

At the scala vestibuli and scala tympani

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20
Q

What are the two types of hair cells located in the organ of Corti?

A

Inner and outer (more numerous) = separated by rods of Corti

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21
Q

Where do the hair cells in the organ of Corti synapse?

A

On bipolar neurons with their cell body in the spiral ganglion

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22
Q

How does hair cell transduction occur?

A

Tectorial membrane vibrates and cilia bend = depending on how they bend, hair cells release neurotransmitters which are captured in nerve fibres

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23
Q

What is the direction of the hair cell K+ current?

A

Inwards = higher K+ concentration than normal in endolymph

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24
Q

What is the membrane potential of endolymph?

A

80mV = generates a 120mV gradient across the stereocilial membrane

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25
Q

What is responsible for recycling K+ in the endolymph?

A

K+ channels, transporters and gap junction network composed of 5 different connexins

26
Q

What can mutations in genes for connexin cause?

A

Deafness

27
Q

What properties allow the basilar membrane to detect different frequencies?

A

Flexible and vibrates in sync with fluid motion

28
Q

What does the width and flexibility of the basilar membrane determine?

A

The distance a particular frequency travels

29
Q

What effect do different frequencies have on hair cells?

A

Activate hair cells maximally at different locations = hair cells are tuned to different frequencies

30
Q

What are some features of inner hair cells?

A

Main source of afferent signal to auditory nerve

10 afferents per hair cell

31
Q

What are some features of outer hair cells?

A

Primarily get efferent input
Control stiffness and amplify membrane vibration
Multiple outer hair cells innervated by single afferent

32
Q

What are the outer hair cells known as?

A

Cochlear amplifiers

33
Q

What is the function of the motor protein prestin that is present in outer hair cells?

A

Located in membrane and can change length of cell

34
Q

How do outer hair cells respond to sound?

A

With both receptor potential and change in length

35
Q

What commonly prescribed drug can inactivate prestin?

A

Furosemide

36
Q

What does a change in length of outer cell allow?

A

Increased basilar membrane movement

37
Q

What are the two mechanisms the auditory nerve has for frequency coding?

A

Place code and temporal code

38
Q

What are the three cochlear nuclei of the auditory nerve?

A

Dorsal cochlear nucleus
Posteroventral cochlear nucleus
Anteroventral cochlear nucleus

39
Q

What does tonotopy ensure?

A

That each neuron innervates several different areas and neuron types

40
Q

What structure is important for localising sound?

A

Lateral superior olive

41
Q

What are some functions of the vestibular system?

A

Provides info about gravity and acceleration
Serves as reference for somatosensory and visual systems
Allows for sense of orientation

42
Q

What structures detect angular and linear head acceleration?

A 
Angular = semicircular canals 
Linear = saccule and utricle
43
Q

What is the function of the peripheral sensory apparatus of the vestibular system?

A

Detects and relays info to the vestibular nucleus about head angular and linear velocity

44
Q

What does the central processing system of the vestibular system do?

A

Processes info in conjunction with other sensory input fro position and movement of head in space

45
Q

What does the motor output system of the vestibular system do?

A

Generates compensatory eye and body movements

46
Q

What is the function of the semicircular canals?

A

Detects head movements via rotatory acceleration

47
Q

What are the crista of the semicircular canals?

A

Sheets of cells where hair cells are clustered

48
Q

What does the ampulla of the semicircular canals contain?

A

Crista = appears as bulge along the canal

49
Q

What are some features of the semicircular canals?

A

1 canal for each major plane

Filled with endolymph

50
Q

What happens to the cupula of the semicircular canal when the head moves?

A

It is displaced by fluid movement

51
Q

Where do the cilia of the semicircular canals project?

A

Into the gelatinous cupula

52
Q

What is the relevance of all the kinocili in the semicircular canals being orientated in the same direction?

A

Means they are all excited or inhibited together

53
Q

What semicircular canals share planes?

A

Horizontal canals share plane with each other

Posterior canal shares plane with contralateral anterior canal

54
Q

What do the semicircular canals form with their contralateral counterparts?

A

Push-pull pairs

55
Q

What is the function of the otolith organs?

A

Sense linear acceleration and gravity

56
Q

What are the otolith organs?

A 
Saccule = movement in vertical plane
Utricle = movement in horizontal plane
57
Q

Where are the hair cells of the otolith organs located?

A

Within the macula = orientated in all directions

58
Q

What are otoconia?

A

Crystals of calcium carbonate located on otolithic membrane

59
Q

What is the function of the striola in the macula?

A

Divides hair cells into two populations with opposing polarities = allows for multidirectional sensitivity

60
Q

What is the forebrain responsible for?

A

Perceived movement

61
Q

What are the vestibular reflexes?

A

Vestibulo-ocular reflex = keeps eyes still in space when head moves
Vestibulo-colic reflex = keeps head still in space when you walk
Vestibulo-spinal reflex = adjusts posture for rapid changes in position

62
Q

Why does alcohol cause loss of balance and dizziness?

A

Alcohol enters cupula which makes it less dense = floats in endolymph more

Neurology (48 decks)

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