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Neuro Physiology > Sensory transduction - auditory and vestibular systems > Flashcards

Sensory transduction - auditory and vestibular systems Flashcards

1
Q

Name the otolith organs

A

Utricle and saccule

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2
Q

Name the semicircular canals

A

Anterior vertical, posterior vertical and horizontal

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3
Q

Give a brief overview of hearing i.e. how is sound processed?

A

Sound -> vibration of air -> vibrate the eardrum, malleus, incus and stapes -> vibration spreads to cochlea -> vibration of air is converted to movement/vibration of fluids in the cochlea -> vibration in the cochlea is captured by hair cells -> transduction -> perceived in the auditory cortex

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4
Q

Name the 3 fluid-filled cavities of the inner ear

A

Scala vestibuli, Scala media, Scala tympani

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5
Q

What separates the scala vestibuli from the scala media?

A

Reissner’s membrane

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6
Q

What separates the scala media from the scala tympani?

A

The basilar membrane

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7
Q

Where does transduction in the inner ear occur?

A

Organ of Corti hair cells, basilar membrane and tectorial membrane

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8
Q

Which fluid filled cavity is closed off at the apex?

A

Scala media

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9
Q

Where do the scala tympani and scala vestibuli connect?

A

Helicotrema

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10
Q

Where is the perilymph continuous?

A

In the scala tympani and scala vestibuli

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11
Q

The scala tympani meets the round window (T/F/)

A

False - meets the oval window!

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12
Q

The scala vestibuli meets the round window (T/F)?

A

True

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13
Q

The basilar membrane is flexible and vibrates in sync with fluid motion. What factors determine the distance a particular frequency of sound travels?

A

The width and flexibility of the BM determines the distance a particular frequency travels i.e. a non-spatial parameter -> spatial representation

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14
Q

Where are hair cells located in the inner ear?

A

Between the basilar membrane and reticular lamina, tips in the tectorial membrane

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15
Q

Where do hair cells synapse?

A

On bipolar neurons with cell body in the spiral ganglion

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16
Q

Describe hair cell transduction

A

Tectorial membrane vibrates -> hair cells cilia bend -> depending on how they bend, neurotransmitter is released -> neurotransmitters are captured in nerve fibres

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17
Q

When hair cells bend most, they fire most. Why is this?

A

Hair cells are tuned to different frequencies

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18
Q

What is different about the hair cell potassium current?

A

The K current is inwards! Higher K concentration than normal in endolymph (conc gradient is inwards)

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19
Q

There are two types of hair cells, inner and outer hair cells. What is the supply and function of each?

A

Inner HC - main source of afferent signal in auditory nerve (CN VIII). Multiple outer HC innervated by a single afferent
Outer HC - primarily get efferent inputs. Control stiffness, amplify membrane vibration

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20
Q

What is sometimes referred to as the ‘cochlear amplifier’?

A

The outer hair cells

21
Q

How do outer hair cells responds to sound?

A

With both a receptor potential and a change in length. Change in length -> increased movement of basilar membrane -> increased bending of inner HC increased -> transduction

22
Q

Name the 3 branches of CN VIII

A

Dorsal cochlear nucleus, posteroventral cochlear nucleus and ante rove trial cochlear nucleus

23
Q

What is tonotopy?

A

Spatial arrangement of where sounds of different frequency are processed in the brain

24
Q

What does the medial superior olive do?

A

Computes sound arrival at the 2 ears, ipsilateral ear earlier than contralateral. This generates an interaural time difference

25
Q

The lateral superior olive neuron gets an excitatory input from the ipsilateral antero-ventral cochlear nucleus. The contralateral AVCN input excites a neuron in the MTNB (medial nucleus of the trapezoid body) which sends an inhibitory signal to the LSO neuron. What happens if the aural signal is closer to the ipsilateral ear?

A

LSO will have a net depolarisation but will have net inhibition if the sound is closer to the other ear. Thus each LSO neuron gets a depolarising (from ipsilateral ear) and hyperpolarising (from contralateral ear) signal and each aural signal stimulates an LSO neuron from each hemisphere. The balance between the two determines the net excitation that is forwarded to the inferior colliculus and the lateral lemniscus

26
Q

The vestibular organ answers two basic questions; where am I going? Which way is up? How does it do this?

A

Head angular acceleration (semicircular canals) - head rotation
Head linear acceleration (saccule and utricle) - translational motion and gravity

27
Q

How many degrees of freedom do all 3D moving bodies have?

A

Six degrees of freedom - 3 translational (linear movements in the x, y and z axes) and 3 rotational (body’s rotation relative to the x, y and z axes)

28
Q

Which part of the internal ear is responsible for translational degrees of movement?

A

Otolith organs - utricle and saccule

29
Q

Which part of the internal ear is responsible for rotational degrees of movement?

A

The semicircular canals

30
Q

What is the function of the semicircular canals?

A

Detect head movements via rotatory acceleration

31
Q

What is the crista?

A

Sheet of cells where hair cells are clustered

32
Q

What is the ampulla of the inner ear?

A

Bulge along canal, contains crista

33
Q

How are kinocili oriented?

A

In the same direction so that they’re all excited or inhibited together

34
Q

Where do cilia project into?

A

Gelatinous cupula

35
Q

How do the semicircular canals work?

A

They are filled with endolymph. Movement causes fluid to circulate and displace cupula

36
Q

Which semicircular canals share the same plane?

A

The horizontal canals

37
Q

Which semicircular canals share contralateral planes?

A

The posterior canal shares a plane with the contralateral anterior canal

38
Q

What do the otolith organs do?

A

Sense linear acceleration and gravity

39
Q

What do the otolith organs consist of and what movements do they sense?

A

Consist of the utricle and the saccule. Utricle - movement in the horizontal plane. Saccule - movement in the vertical/sagittal plane

40
Q

Where do hair cells lie within the otolith organs?

A

The macula

41
Q

What is the name of the structure that divides the hair cells into two populations with opposing polarities?

A

Striola

42
Q

What are otoconia?

A

Crystals of calcium carbonate that lie on the otolithic membrane

43
Q

Other than dividing the hair cells into 2 populations of opposite polarity what else does the striola do?

A

Arranges otoconia into narrow trenches dividing each otolith. Allows otolith organs to have multidirectional sensitivity

44
Q

What is the function of the vestibulo-ocular reflex?

A

Keeps the eyes still in space when the head moves

45
Q

What is the function of the vestibulo-colic reflex?

A

Keeps the head still in space - or on a level plane when you walk

46
Q

What is the function of the vestibular-spinal reflex?

A

Adjusts posture for rapid changes in position

47
Q

Name some examples of substances that can cause ototoxicity

A

Aminoglycoside antibiotics e.g. gentamicin. Chemotherapy agents. Alcohol (transient)

48
Q

Why can alcohol cause dizziness?

A

Alcohol is less dense than water. When you drink alcohol, it enters the blood and then the cupula. The cupula becomes less dense and floats in the endolymph more. The cupula bends more than usual away from the ground which bends hair cells, as if you are rotating, even when you are still. This gives you the sensation of spinning

Neuro Physiology (9 decks)

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