Sensory Transduction

Question 1

What is the role of the hair cell?

Answer 1

Transduces the stimulus

Question 2

What are the cilia responsible for?

Answer 2

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

Question 3

What regulates the response of cilia to a stimulus?

Answer 3

Afferent nerves

Question 4

What are the tip links of hair cells?

Answer 4

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

Question 5

What does the tonic release of glutamate from cilia allow?

Answer 5

Modulation of AP frequency

Question 6

What is sound?

Answer 6

Repetitive variation in a medium (e.g air)

Question 7

How does sound travel?

Answer 7

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

Question 8

What effect does sound have on the ear?

Answer 8

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

Question 9

What captures vibration in the cochlea?

Answer 9

Hair cells = physical vibration is transduced to neural energy

Question 10

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

Answer 10

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

Question 11

What does the inner ear contain?

Answer 11

3 fluid filled cavities

Question 12

What does Reissner’s membrane separate?

Answer 12

Scala vestibuli and scala media

Question 13

What does the basilar membrane separate?

Answer 13

Scala media and scala tympani

Question 14

Where is the scala media closed off?

Answer 14

At the apex

Question 15

Where are the scala tympani and scala vestibuli connected?

Answer 15

At the helioctrema

Question 16

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

Answer 16

Oval window = scala tympani

Round window = scala vestibuli

Question 17

Where are hair cells located in the organ of Corti?

Answer 17

Between the basilar membrane and reticular lamina

Question 18

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

Answer 18

The tectorial membrane

Question 19

Where in the inner ear is the perilymph continuous?

Answer 19

At the scala vestibuli and scala tympani

Question 20

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

Answer 20

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

Question 21

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

Answer 21

On bipolar neurons with their cell body in the spiral ganglion

Question 22

How does hair cell transduction occur?

Answer 22

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

Question 23

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

Answer 23

Inwards = higher K+ concentration than normal in endolymph

Question 24

What is the membrane potential of endolymph?

Answer 24

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

Question 25

What is responsible for recycling K+ in the endolymph?

Answer 25

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

Question 26

What can mutations in genes for connexin cause?

Answer 26

Deafness

Question 27

What properties allow the basilar membrane to detect different frequencies?

Answer 27

Flexible and vibrates in sync with fluid motion

Question 28

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

Answer 28

The distance a particular frequency travels

Question 29

What effect do different frequencies have on hair cells?

Answer 29

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

Question 30

What are some features of inner hair cells?

Answer 30

Main source of afferent signal to auditory nerve | 10 afferents per hair cell

Question 31

What are some features of outer hair cells?

Answer 31

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

Question 32

What are the outer hair cells known as?

Answer 32

Cochlear amplifiers

Question 33

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

Answer 33

Located in membrane and can change length of cell

Question 34

How do outer hair cells respond to sound?

Answer 34

With both receptor potential and change in length

Question 35

What commonly prescribed drug can inactivate prestin?

Answer 35

Furosemide

Question 36

What does a change in length of outer cell allow?

Answer 36

Increased basilar membrane movement

Question 37

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

Answer 37

Place code and temporal code

Question 38

What are the three cochlear nuclei of the auditory nerve?

Answer 38

Dorsal cochlear nucleus Posteroventral cochlear nucleus Anteroventral cochlear nucleus

Question 39

What does tonotopy ensure?

Answer 39

That each neuron innervates several different areas and neuron types

Question 40

What structure is important for localising sound?

Answer 40

Lateral superior olive

Question 41

What are some functions of the vestibular system?

Answer 41

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

Question 42

What structures detect angular and linear head acceleration?

Answer 42

``` Angular = semicircular canals Linear = saccule and utricle ```

Question 43

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

Answer 43

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

Question 44

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

Answer 44

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

Question 45

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

Answer 45

Generates compensatory eye and body movements

Question 46

What is the function of the semicircular canals?

Answer 46

Detects head movements via rotatory acceleration

Question 47

What are the crista of the semicircular canals?

Answer 47

Sheets of cells where hair cells are clustered

Question 48

What does the ampulla of the semicircular canals contain?

Answer 48

Crista = appears as bulge along the canal

Question 49

What are some features of the semicircular canals?

Answer 49

1 canal for each major plane | Filled with endolymph

Question 50

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

Answer 50

It is displaced by fluid movement

Question 51

Where do the cilia of the semicircular canals project?

Answer 51

Into the gelatinous cupula

Question 52

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

Answer 52

Means they are all excited or inhibited together

Question 53

What semicircular canals share planes?

Answer 53

Horizontal canals share plane with each other | Posterior canal shares plane with contralateral anterior canal

Question 54

What do the semicircular canals form with their contralateral counterparts?

Answer 54

Push-pull pairs

Question 55

What is the function of the otolith organs?

Answer 55

Sense linear acceleration and gravity

Question 56

What are the otolith organs?

Answer 56

``` Saccule = movement in vertical plane Utricle = movement in horizontal plane ```

Question 57

Where are the hair cells of the otolith organs located?

Answer 57

Within the macula = orientated in all directions

Question 58

What are otoconia?

Answer 58

Crystals of calcium carbonate located on otolithic membrane

Question 59

What is the function of the striola in the macula?

Answer 59

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

Question 60

What is the forebrain responsible for?

Answer 60

Perceived movement

Question 61

What are the vestibular reflexes?

Answer 61

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

Question 62

Why does alcohol cause loss of balance and dizziness?

Answer 62

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