6: Physiology - Sensory transduction: auditory and vestibular system

Question 1

Which cells, found in the inner ear, convert sound energy (moving them) into action potentials?

Answer 1

Hair cells (stereocilia)

Question 2

Hair cells are connected to ___ ___ neurons.

Answer 2

special sensory

Question 3

What excites stereocilia?

Answer 3

Movement by sound energy

Question 4

Which channels are found at the tips of stereocilia?

What enters when they are open?

Answer 4

Tip links

K+ (which ENTERS unusually and depolarises the membrane)

Question 5

When stereocilia are excited by movement and the opening of tip link channels, the sensory neurons connected to them are EXCITED.

Which neurotransmitter is released to cause an excitatory action potential?

Answer 5

Glutamate

Question 6

Hair cells are found throughout the labyrinth of the inner ear, which is responsible for hearing and balance.

The function of hair cells changes based on their ___ in the labyrinth.

Answer 6

position

Question 7

What properties of a sound wave match to

a) pitch
b) volume?

Answer 7

a) Frequency

b) Amplitude

Question 8

Why do vibrations received by the tympanic membrane need to be amplified before they pass into the cochlea?

Answer 8

It takes more energy to vibrate fluid compared to air

Question 9

Which bones are mostly responsible for amplifying the vibrations received by the tympanic membrane?

Answer 9

Ossicles

Question 10

Which chamber in the Organ of Corti contains the hair cells?

Answer 10

Scala media

Question 11

Which membrane do hair cells sit on in the Organ of Corti?

Answer 11

Basilar membrane

Question 12

What properties of the basilar membrane allow to discriminate between sounds of different pitches?

Answer 12

Oval window end (the base) is wide and flexible

Apex is narrow and stiff

So different energy levels i.e pitches of sound are required to move the hair cells depending on what end you’re at

Question 13

Which membranes are found

a) superior to
b) inferior to

hair cells in the Organ of Corti?

Answer 13

a) Tectorial / Reissner’s membrane

b) Basilar membrane

Question 14

The basilar membrane changes the ___ of hair cells by bending in response to sound energy.

The tectorial membrane actively ___ hair cells by vibrating.

Answer 14

basilar membrane changes hair cell position

tectorial membrane moves hair cells by vibrating

Question 15

The potassium concentration of the fluid surrounding hair cells (?endolymph) is (high / low).

Answer 15

high K+ concentration

Question 16

In which direction does potassium move when the tip links of hair cells are open?

Why?

Answer 16

Inwards

K+ concentration in endolymph is high

Question 17

Which fluid is found in the scala media?

Answer 17

Endolymph

Question 18

Which fluid is found in the scala vestibuli and scala tympani?

Answer 18

Perilymph

Question 19

What happens to the potassium which enters hair cells through tip links?

Answer 19

After action potential K+ is recycled back into scala media to keep conc. gradient the same

Question 20

How are hair cells arranged in the Organ of Corti?

Answer 20

Outer layer

Inner layer

Question 21

Which layer of hair cells is concerned primarily with sensory input?

Answer 21

Inner layer

Question 22

Which nerve carries the sensory neurons from the inner hair cells?

Answer 22

Cochlear part of CN VIII

Question 23

Each inner hair cell is supplied by (a single / many) sensory neuron(s).

Answer 23

each inner hair cell has its own sensory neuron

Question 24

What is the primary function of outer hair cells?

Answer 24

Movement of the tectorial membrane to enhance vibration

Question 25

How many **outer hair cells** are connected to each **somatic efferent** fibre?

Answer 25

**Many**

Question 26

Where do **sensory neurons synapse** between the **inner hair cells** and **CN VIII**?

Answer 26

**Spiral ganglion**

Question 27

superior olivary ganglion somatic efferents outer hair cells

Question 28

sensory coding of pitch depends on firing rate of hair cells AND where they are on the basilar strip

Question 29

On which **side** of the brain are **auditory signals** processed?

Answer 29

**Both** processing is bilateral

Question 30

Briefly describe how **auditory stimuli** reach the **primary auditory cortex** from the **inner ear**.

Answer 30

CN VIII fibres \> Spiral ganglion \> Cochlear nucleus \> Superior olivary nucleus \> Inferior colliculus \> Medial geniculate nucleus \> Primary auditory cortex sorry

Question 31

Briefly describe how **visual stimuli** reach the **visual cortex** from the **eyes**.

Answer 31

**CN II fibres \> Lateral geniculate nucleus \> Superior colliculus \> Visual cortex**

Question 32

What **information** does the sensory pathway use to **localise the position of sound?**

Answer 32

**1. When it is heard** **2. Volume** both different for each ear

Question 33

What **sense** is the vestibular system broadly concerned with?

Answer 33

**Balance**

Question 34

Which parts of the **vestibular system** detect a) head rotation b) linear acceleration (e.g side to side, front to back, head tilt on one plane)?

Answer 34

**a) Semicircular canals** **b) Otolith organs (saccule and urticle)**

Question 35

How are **hair cells** involved in the vestibular system?

Answer 35

**Different movements** cause movements in **fluid and otolith** which move the hair cells

Question 36

What **movements** are detected by the **semicircular canals?**

Answer 36

**Rotation**

Question 37

Which **fluid** is found in the **semicircular canals**?

Answer 37

**Perilymph**

Question 38

In the **semicircular canals, (perilymph / endolymph)** exerts force on hair cells during ___ movement.

Answer 38

**perilymph** **rotational movement**

Question 39

Which **type** of sensory signal is generated by the hair cells on the a) **ipsilateral side** b) **contralateral side** of a head movement?

Answer 39

**a) Excitatory** **b) Inhibitory** b acts as a confirmation to the brain that the movement is occurring

Question 40

Which **cranial nerve** receives the sensory impuses from the **vestibular organs**?

Answer 40

**Vestibular part of CN VIII**

Question 41

Which part of the **vestibular system** detects **acceleration on one plane** and **gravity**?

Answer 41

**Otolith organs**

Question 42

What are the two **otolith organs**?

Answer 42

**Saccule** **Urticle**

Question 43

Which **otolith organ** is responsible for detecting linear movement **a) vertically** **b) horizontally?**

Answer 43

**a) Saccule** **b) Utricle** u for up and then the opposite of that kill me

Question 44

Which **substance** exerts on a force on the hair cells in the **otolith organs** during **linear movements?**

Answer 44

**Otolith** calcium carbonate crystals

Question 45

Which **reflex** keeps the eyes focused during head movement?

Answer 45

**Vestibulo-ocular reflex**