Vestibular and Audition

Question 1

What are the primary functions of the vestibular system?

Answer 1

The primary functions of the vestibular system include detecting head position, as well as linear and angular acceleration. It plays a key role in integrating balance, gravity, posture, and spatial orientation.

Question 2

Where is the vestibular system located?

Answer 2

In the inner ear, as part of the vestibular labyrinth, a fluid-filled structure adjacent to the cochlea.

Question 3

What are the two main components of the vestibular system?

Answer 3

1. Semicircular canals (for rotational acceleration)
2. Otolith organs: utricle and saccule (for linear acceleration and head tilt)

Question 4

How do otolith organs transduce motion?

Answer 4

Hair cells embedded in a gelatinous layer are topped with otoliths (calcium carbonate crystals); when the head moves, otoliths shift, bending stereocilia and triggering depolarization.

Question 4

What do the utricle and saccule detect?

Answer 4

Utricle → horizontal linear acceleration
Saccule → vertical linear acceleration and gravity

Question 5

How do semicircular canals detect movement?

Answer 5

Endolymph movement within the canals bends hair cells in the ampullae, detecting angular acceleration in 3 planes.

Question 6

What role do vestibular hair cells play?

Answer 6

Act as mechanoreceptors; bending toward the kinocilium causes depolarization, away causes hyperpolarization → modifies firing of the vestibular nerve.

Question 7

What cranial nerve carries vestibular signals to the brain?

Answer 7

Vestibular branch of Cranial Nerve VIII (Vestibulocochlear nerve).

Question 8

Where does vestibular information go in the brain?

Answer 8

Vestibular nuclei (pons/medulla), cerebellum, spinal cord, and oculomotor nuclei (for reflexes like VOR).

Question 9

What is the Vestibulo-Ocular Reflex (VOR)?

Answer 9

Reflex that stabilizes vision by moving the eyes in the opposite direction of head movement to maintain a stable retinal image.

Question 10

What type of energy is sound?

Answer 10

Acoustic energy – pressure waves caused by the displacement of air molecules.

Question 11

What are the two main physical properties of sound?

Answer 11

1. Amplitude (loudness, measured in dB)
2. Frequency (pitch, measured in Hz)

Question 12

What is the human hearing range?

Answer 12

Approximately 20 Hz – 20,000 Hz; high-end sensitivity declines with age.

Question 13

What is the function of the outer ear?

Answer 13

The pinna collects sound waves; the ear canal amplifies and funnels sound to the tympanic membrane.

Question 14

What are the ossicles, and what do they do?

Answer 14

Malleus, incus, and stapes – they transmit and amplify vibrations from the tympanic membrane to the oval window of the cochlea.

Question 15

What is the cochlea, and how is it organized?

Answer 15

A fluid-filled spiral structure divided into three chambers; it contains the basilar membrane and the Organ of Corti, where sound transduction occurs.

Question 16

What is tonotopy?

Answer 16

Spatial arrangement in the cochlea where different regions respond to specific frequencies: high frequencies near the base, low frequencies near the apex.

Question 17

How does cochlear transduction work?

Answer 17

Sound-induced vibrations move the basilar membrane, bending hair cells in the Organ of Corti → K⁺ influx → depolarization → neurotransmitter release → cochlear nerve activation.

Question 18

What is the pathway of auditory information to the brain?

Answer 18

Sound wave → Tympanic membrane → Ossicles → Oval window → Cochlea → Hair cells (organ of Corti) → Auditory nerve (CN VIII) → Cochlear nuclei → Superior olivary complex → Inferior colliculus → Medial geniculate nucleus (thalamus) → Primary auditory cortex

Question 19

What is the acoustic reflex?

Answer 19

A protective reflex where small muscles (tensor tympani and stapedius) contract in response to loud sounds (70–100 dB) to reduce ossicle movement and protect the cochlea.

Question 20

What cranial nerve serves both the vestibular and auditory systems?

Answer 20

Cranial Nerve VIII – the vestibulocochlear nerve.

Question 21

How are both systems similar in terms of transduction?

Answer 21

Both use hair cells as mechanoreceptors that depolarize in response to mechanical displacement (fluid or crystal movement).

Question 22

How do these systems integrate with motor control?

Answer 22

The vestibular system interacts with the cerebellum and spinal cord for balance and posture; the auditory system aids in sound localization and orientation reflexes.

Question 23

Why is the vestibular system essential for visual stability?

Answer 23

Through the VOR, it ensures that eye movements compensate for head movements to stabilize gaze.

Question 24

What reflex arc is shared in concept by both systems?

Answer 24

Both involve rapid, automatic responses (vestibulo-ocular reflex, acoustic reflex) mediated by brainstem circuits for protection and coordination.

Question 25

Signal transduction (vestibular system)

Answer 25

Occurs in hair cells of the semicircular canals and otolith organs. Movement of endolymph bends stereocilia. Bending toward the kinocilium = depolarization → more neurotransmitter release. Bending away = hyperpolarization → less neurotransmitter. Signals sent via vestibular branch of CN VIII to brainstem & cerebellum.

Question 26

Signal Transduction (Auditory System)

Answer 26

Occurs in hair cells in the Organ of Corti (within the cochlea). Sound waves → vibration of basilar membrane → deflection of stereocilia. Stereocilia bend against the tectorial membrane. K⁺ influx from endolymph causes depolarization → neurotransmitter release. Signal sent via cochlear branch of CN VIII to auditory brainstem nuclei.

Question 27

Which brain areas receive projections from the vestibular system?

Answer 27

Vestibular nuclei in the brainstem, cerebellum, thalamus, spinal cord, and regions of the cortex (e.g. parietal cortex for perception of self-motion and orientation).

Question 28

What do the utricle and saccule detect?

Answer 28

Linear acceleration and static head position relative to gravity.

Question 29

What do the semicircular canals detect?

Answer 29

Rotational acceleration of the head.

Question 30

How do otoliths help detect linear acceleration?

Answer 30

They are calcium carbonate crystals that exert pressure on hair cells' cilia during head tilt or movement, triggering electrical impulses.

Question 31

What is the function of the vestibular hair cells?

Answer 31

Bending of cilia leads to depolarisation, releasing neurotransmitter and activating the vestibular nerve.

Question 32

Where does the vestibular nerve project to?

Answer 32

Vestibular nuclei in the medulla and pons, then to the cerebellum and spinal cord.

Question 33

Which brain areas receive projections from the vestibular system?

Answer 33

Vestibular nuclei in the brainstem, cerebellum, thalamus, spinal cord, and regions of the cortex (e.g. parietal cortex for perception of self-motion and orientation).

Question 34

What is the role of the cerebellum in the vestibular system?

Answer 34

Coordinates balance and posture by integrating vestibular input with proprioceptive and visual information.

Question 35

How does the vestibular system contribute to postural control?

Answer 35

Via projections to the spinal cord that influence motor neurons for balance adjustments.

Question 36

What is vestibular compensation?

Answer 36

Neural adaptation that allows recovery of balance function after damage to vestibular input (e.g. via plasticity in the cerebellum and brainstem). uses visual and proprioception information

Question 37

How does the basilar membrane contribute to frequency discrimination?

Answer 37

It is tonotopically organized: base responds to high frequencies, apex to low frequencies.

Question 38

What is the path of auditory information from the cochlea to the cortex?

Answer 38

Cochlear nerve → cochlear nucleus → superior olivary complex → inferior colliculus → medial geniculate nucleus (thalamus) → primary auditory cortex (A1).

Question 39

What is the function of the superior olivary complex?

Answer 39

Detects interaural time and intensity differences to localize sound in space.

Question 40

What does the medial geniculate nucleus (MGN) do?

Answer 40

Acts as a relay in the thalamus for auditory information heading to the auditory cortex.

Question 41

Where is the primary auditory cortex located and how is it organized?

Answer 41

In the temporal lobe; it is tonotopically organized (like the cochlea).

Question 42

What physiological effects occur with loud and/or constant noise exposure?

Answer 42

1) Increased blood pressure, (2) Muscle tension, (3) Release of stress hormones.

Question 43

What is the fight-or-flight response, and how is it related to noise?

Answer 43

It’s a physiological reaction to perceived threat; loud noises can trigger this response via stress hormone release and nervous system arousal.

Question 44

What are potential health effects of excessive and prolonged noise exposure?

Answer 44

Anxiety, depression, cardiovascular disease, and chronic stress.

Question 45

What proportion of people are frequently exposed to harmful noise?

Answer 45

Approximately 20%.

Question 46

What is the Default Mode Network (DMN)?

Answer 46

A network of interconnected brain areas that are active during rest or internal focus (e.g. daydreaming, self-reflection, mind-wandering).

Question 47

When is the DMN most active?

Answer 47

When a person is not focused on external tasks, especially during introspection or rumination.

Question 48

What kind of mental activity is often associated with DMN activation?

Answer 48

Mind chatter, including stress, anxiety, and negative rumination.

Question 49

What was the main method used in the Feinstein study to reduce DMN activity?

Answer 49

Float therapy – participants underwent 3 × 90-minute float sessions over 3 weeks.

Question 50

What kind of study design was used in the Feinstein float study?

Answer 50

Within-subjects design – each participant’s pre-fMRI was compared to their post-fMRI.

Question 51

What effect did float therapy have on DMN activity?

Answer 51

DMN activity decreased after float sessions, helping reduce internal chatter and stress.

Question 52

What automatic auditory function helps prevent sudden noise inputs from overwhelming us?

Answer 52

The acoustic reflex – tiny muscles (e.g. tensor tympani and stapedius) contract to dampen loud sounds and protect the inner ear.

Question 53

How can loud noises affect balance?

Answer 53

Loud noises can stimulate the vestibular system (shared pathways in the inner ear), potentially causing disorientation or imbalance due to overstimulation.

Question 54

What is the role of descending fibres from the cerebellum to the spinal cord?

Answer 54

They allow the cerebellum to correct movement errors by adjusting muscle activity and posture through the spinal cord—helping maintain balance and coordination.

Question 55

What is the perceived change in loudness with decibels, and can you give examples of safe, damaging, and painful sound levels?

Answer 55

Decibels (dB) are logarithmic: every 10 dB increase sounds ~10x louder to the human ear. 🫁 10 dB – Breathing (Safe) 🏍️ 100 dB – Motorcycle engine (Damaging with prolonged exposure) 🔫 160 dB – Shotgun blast (Painful and damaging instantly) Under 70 dB: Generally safe 85+ dB: Prolonged exposure can cause hearing damage 120+ dB: Pain threshold 140+ dB: Immediate damage possible

Question 56

What do the malleus, incus, and stapes do in the auditory system?

Answer 56

Malleus (Hammer): Function: Receives vibrations from the eardrum (tympanic membrane) and transmits them to the incus. Incus (Anvil): Function: Receives vibrations from the malleus and passes them to the stapes. Stapes (Stirrup): Function: Transmits vibrations from the incus to the oval window of the cochlea, which is the start of the inner ear. The movement of the stapes at the oval window creates fluid motion in the cochlea, which stimulates auditory receptors.