Physiology- Visual, Auditory and Vestibular System

Question 1

Describe the opening and closing of transduction channels in hair cells

Answer 1

Force towards kinocilium opens TRPA1 channels & K+ enters, depolarising cell. Force away shuts channels
Tip links- connect transduction channels (cation channels on hairs)

Question 2

Describe hair cell transduction

Answer 2

Tectorial membrane vibrates
Hair cells’ cilia bend
Depending on how they bend, hair cells release neurotransmitter
Neurotransmitter is captured in nerve fibres
Neural energy is sent to the brain

Question 3

What are the two hair cell types of the auditory system?

Answer 3

Inner and outer

Question 4

Describe inner hair cells

Answer 4

Main source of afferent signal in CNVIII nerve (~10 afferents per hc). Multiple outer HC innervated by single afferent

Question 5

Describe outer hair cells

Answer 5

Primarily get efferent inputs. Control stiffness, amplify membrane vibration (more outer than inner)

Question 6

What is the motor protein present in outer hair cells?

Answer 6

Prestin- can change the length of the cell

Question 7

What direction is the Hair cell K+ current?

Answer 7

Inwards

Question 8

What is critical for reconstituting K+ in the endolymph?

Answer 8

K channels, transporters and gap junction networks composed of 5 different connexions are critical for reconstituting K+ in the endolymph

Question 9

What are the two mechanisms for frequency coding?

Answer 9

Place and temporal code

Question 10

What is place code for?

Answer 10

Pitch

Question 11

What is temporal code for?

Answer 11

Higher frequencies

Question 12

What is the central pathway in the auditory system?

Answer 12

Cochlea
CNVIII
Cochlear nuclei (medulla)
Superior olivary nuclei (pons)
Nucleus of lateral lemniscus (pons)
Inferior colliculus and medial geniculate nucleus (Midbrain)
Primary auditory cortex

Question 13

What are the 3 cochlear nuclei?

Answer 13

Dorsal cochlear nucleus

Posteroventral and anteroventral cochleal nuclei

Question 14

What does the medial superior olive do?

Answer 14

Computes sound arrival at the two ears…ipsilateral ear earlier than contralateral. This generates an “interaural time difference”…….uses a “delay line”

Question 15

What movement does the saccule sense?

Answer 15

Vertical/sagittal plane

Question 16

What movement does the utricle sense?

Answer 16

Horizontal plane

Question 17

What does the striola of the macula do?

Answer 17

Serves as landmark
Arranges otoconia into narrow trenches dividing each otolith
Orientation of the hair cells change over the course of the macula
Allows otolith organs to have multidirectional sensitivity

Question 18

What signals exist in the vestibular nerve?

Answer 18

Tonic- deviations from which are proportional to head velocity

Question 19

What signals exist in the macular (sensory epithelium vestibule) afferents?

Answer 19

Tonic- deviations from which are sensitive to acceleration

Question 20

What is the vestibulo-ocular reflex?

Answer 20

Keeps eyes still in space when head moves

Question 21

What is the vestibulo-colic reflex?

Answer 21

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

Question 22

What is the vestibulo-spinal reflex?

Answer 22

Adjusts posture for rapid changes in position

Question 23

What is the organisation of the entire visual field on the primary visual field described as?

Answer 23

Visuotopic

Question 24

What segregation occurs of the retinal output?

Answer 24

Segregation of cells representing movement and form in the LGN and V1

Question 25

What are the inputs to the striate cortex?

Answer 25

Magnocellular LGN neurons: Project to layer IVCalpha
Parvocellular LGN neurons: Project to layer IVCbeta
Koniocellular LGN axons: Bypasses layer IV to make synapses in layers II and III (blobs, visible after cytochrome oxidase staining)

Question 26

Where are the first binocular neurons found?

Answer 26

In striate cortex (most layer III neurons are binocular, but not layer IV)

Question 27

Describe the cortical receptive fields

Answer 27

Orientation Selectivity/ive neurons
Respond to light/dark bars or edges
Only if in a particular orientation
Peak frequency depends on angle, preferred orientation
All edges representations were equally represented