Vestibular & Audition System

Question 1

What is the vestibular sense?

Answer 1

Sense of balance; mixed info of balance, gravity and posture = spatial awareness.

Question 2

What is the vestibular sense essential for?

Answer 2

Coordinated movement.

Question 3

How does the brain get information on position, acceleration & movement?

Answer 3

Combine proprioception & equilibrioception.

Question 4

What is the vestibular labyrinth?

Answer 4

set of connected, fluid-filled tubes in inner ear, extending from the cochlea

Question 5

What does the vestibular system do?

Answer 5

Provide info on body position relative to gravity.

Critical for balance (equilibration)

Question 6

What is the fluid in the inner ear tubes, and how is it balanced?

Answer 6

Endolymph - produced continuously & contains sodium + potassium

Drained by a duct = fluid balance regulated in fluid sacs (sacculus & utricle)

Question 7

What are the 5 regions of interest in the vestibular system?

Answer 7

2 otolith organs: utricle (linear acceleration) + sacculus (static position)

3 semicircular canals: rotational accelerations of head

Question 8

Where do the vestibular hair cells (cilia) sit?

Answer 8

In the otolith organs & semicircular canals.

Question 9

What are otoliths?

Answer 9

Crystals of calcium carbonate in the otolith organs that exert weight onto cilia of hair cells.

Question 10

What happens when the head is in a normal upright position?

Answer 10

Otolith presses down on sensory hair cells in otolith organs (utricle & saccule); prevents cilia from moving side-to-side

Question 11

What happens when the head is tilted?

Answer 11

Gravity pulls on otoliths –> pulls cilia down –> hair cell fire electrical impulse (signal transduction via mechanoreception)

When accelerating / decelerating, otoliths pull cilia back / forwards + sideways

Question 12

When hair cells _____, they _____ and release _______, which activates ______ of the _______ nerve.

Answer 12

bend; depolarise; transmitters; afferents; vestibular

Question 13

What is the vestibular nerve?

Answer 13

Vestibular branch of cranial nerve 8

Question 14

What does the vestibular nerve do?

Answer 14

Projects to multiple vestibular nuclei in the medulla and pons of brainstem –> cerebellum

Question 15

The vestibular system is the only sensory nerve to do what?

Answer 15

Directly innervate the cerebellum

Question 16

What could the cerebellum be for?

Answer 16

Error checker; corrects mismatch in balance through recalibration and communicating with other parts of brain

Question 17

Aside from the typical vestibular areas, where else does sensory information go?

Answer 17

Spinal cord, which helps in quick movement (specifically portions of CN8 innervated by otolith organs’ hair cells)

Question 18

Where else does the sensory fibres also descend from to the spinal cord?

Answer 18

Cerebellum

Question 19

What is the vestibular ocular reflex? (VOR)

Answer 19

Involuntary reflex
- stabilises vision during head movements
- counter rotates the eyes in the opp direction = clear & stable image maintained on retina

Question 20

What is acoustic energy?

Answer 20

Energy disturbance passing through matter in the form of waves (soundwaves)

Question 21

What does the auditory system consist of?

Answer 21

Outer, middle & inner ear + neural pathway to cortex

Question 22

What is the stimulus for audition?

Answer 22

Mechanical displacement of molecules in a medium, caused by changing pressure (ripple effect)

Question 23

Do you need a medium to have sound?

Answer 23

Yes; sound cannot progress through a vacuum where there are no molecules to disturb.

Usually through gas, but can be through liquids & solids too.

Question 24

What are the two key features of sound waves?

Answer 24

Amplitude & frequency

Question 25

What is amplitude in sound waves?

Answer 25

Displacement from baseline (y axis) Relates to loudness; large disturbance in molecules = large amplitude

Question 26

What is frequency in soundwaves?

Answer 26

Related to pitch; time period (distance b/w crests or peaks on x axis) Shorter time period = higher frequency

Question 27

What is frequency measured in?

Answer 27

Hertz (Hz) - 1 Hz = 1 per second Frequency (f) = 1/time period

Question 28

How is the intensity of noise measured?

Answer 28

In decibe units (dB)

Question 29

How do humans perceive loudness?

Answer 29

Across a range of amplitudes, so dB scale is logarithmic. Ear hears only the significant multiplying of the energy of sound, not very small changes

Question 30

What are the orders of magnitude?

Answer 30

Perceived changes

Question 31

What is the range of frequencies in which humans can perceive pitch?

Answer 31

20 - 20000 Hz

Question 32

Does the acoustic range for humans change across our lifespan?

Answer 32

Yes. Frequencies over 17 kHz is only perceptible by people under 25 on average

Question 33

What is this "Sonic Teenager Deterrent" aka "Mosquito Box"?

Answer 33

A device that emits 80dB at 17 KHz (lower than human range), to make teenagers feel uncomfortable and leave a place (prevent loitering)

Question 34

What are the processes of the auditory system?

Answer 34

Acoustic energy reaches outer ear (pinna / auricle) --> funnelled into ear canal --> sound amplified --> ear drum (tympanic membrane)

Question 35

What happens when the acoustic energy hits the tympanic membrane?

Answer 35

It vibrates, matching frequency of incoming soundwaves. These vibrations are channelled through 3 ossicles (bones of middle ear).

Question 36

What are the three ossicles?

Answer 36

Malleus (hammer) Incus (anvil) Stapes (stirrup)

Question 37

How do the ossicles interact with each other?

Answer 37

Malleus connected to tympanic membrane, so membrane movement = malleus movement --> moves incus, which moves the stapes

Question 38

What is the stapes connected to?

Answer 38

The cochlea: snail-shaped, fluid-filled chamber in inner ear

Question 39

How long is the cochlea?

Answer 39

34 mm long

Question 40

How does the stapes interact with the cochlea?

Answer 40

Sends vibrations through fluid in cochlea by moving the oval window

Question 41

What is inside the cochlear duct?

Answer 41

Organ of Corti, home of many hair cells sitting on basilar membrane, which bends as vibrations travel

Question 42

Does the frequency of a sound input vibrate some locations in the membrane more than other locations? What are the two terms for this?

Answer 42

Yes. Frequency-to-place conversion & tonotopic mapping

Question 43

What do cochlear hair cells do when they bend?

Answer 43

Release transmitter, inducing signal transduction. Synapse onto spiral ganglion cells, whose axons are part of cochlear nerve (auditory branch of CN 8), so signals are sent to brain

Question 44

What is the acoustic reflex?

Answer 44

Involuntary contraction of muscles attached to stapes and malleus

Question 45

How does the acoustic reflex work?

Answer 45

Muscles contract when intense sound stimuli present (70 - 100dB, depending on idividual) Reduce ossicle movement so they can't transmit force to cochlea efficiently decrease pressure transmission to cochlea by 15 - 30dB

Question 46

Is the acoustic reflex a good protection against loud noises?

Answer 46

Not really; takes 10 - 100ms to initiate reflex, so can't protect against sudden intense noises. Reduction of dB isn't that much.

Question 47

How do we perceive pitch?

Answer 47

Hair cells become active in displaced regions of membrane, sending frequency-specific neural signals to brain

Question 48

How do we perceive loudness?

Answer 48

More hair cells fire when there is greater sound pressure level, so there is greater amplitude of membrane displacement.

Question 49

What coding schemes occur in pitch & loudness perception?

Answer 49

Rate-place coding (depends on rate & place)