M3 L7

Question 1

What does the outer ear include?

Answer 1

the pinna and auditory canal.

Question 2

What does the pinna do? Why important?

Answer 2

The pinna directs sound waves into the ear.

The shape of the pinna makes us more sensitive to sounds coming from ahead than from behind. The convolutions in the pinna play a role in localizing sounds.

Question 3

What does the auditory canal do?

Answer 3

helps channel sound towards the tympanic membrane (eardrum).

Question 4

What does the middle ear include?

Answer 4

the tympanic membrane

Question 5

what is the tympanic membrane? What is it attached to and what do they do.

Answer 5

it is the eardrum. it is the first structure that receives sound vibrations.

The eardrum is attached to three small bones called the ossicles (malleus, incus, and stapes). These bones amplify vibrations and transfer them from air (outer/middle ear) to fluid (inner ear).

Question 6

What does the stapes do?

Answer 6

acts as the final step in converting air vibrations into fluid vibrations.

Question 7

What two muscles does the middle ear contain and what do they do?

Answer 7

Tensor tympani muscle
Stapedius muscle

• prevent saturation
• regulate loud sound

Question 8

Tensor tympani muscle
* function/purpose
* what is it attached to
* stimulated by what nerve?

Answer 8

The main role of the tensor tympani is to dampen loud sounds by pulling on the malleus. This reduces the vibration of the tympanic membrane (eardrum).

• attached to bone in cavity of middle ear on one end and malleus at other end
• stimulated by trigemninal nerve

Question 9

The Stapedius muscle
* function/purpose
* what is it attached to
* stimulated by what nerve?

Answer 9

The stapedius muscle reduces excessive movement of the stapes by pulling it away from the oval window.

• attached to bone in the cavity of the middle ear on one end and stapes at other end
• stimulated by facial nerve

Question 10

What does the inner ear contain? what is it

Answer 10

the cochlea, a fluid-filled structure responsible for sound transduction.

• also the vestibule and semicircular canals

Question 11

What does the cochlea do

Answer 11

Vibrations in the cochlea cause movement in hair cells, generating action potentials (APs) that send auditory signals to the brain.

Question 12

vestibule function?

Answer 12

These structures detect linear acceleration (e.g., moving forward in a car, going up in an elevator). Help maintain static equilibrium (posture and head position relative to gravity).

Question 13

semicircular canals?

Answer 13

Detect rotational movements (e.g., turning your head left or right, tilting your head). Each canal is filled with endolymph which senses changes in head position.

Important for dynamic equilibrium (maintaining balance during movement).

Question 14

What is the Attenuation Reflex

Answer 14

a protective mechanism of the ear that reduces the impact of loud sounds by dampening their transmission to the inner ear.

• makes sure sounds dont saturate the response of receptors in inner ear

Question 15

Limit of the Attenuation Reflex?

Answer 15

Delay of 50–100 msec and therefore less protective when there is a very sudden loud sounds

Question 16

What frequency does the attenuation reflex suppress?

Answer 16

Suppresses low frequencies more than high frequencies
* it tends to make high-frequency sounds easier to discern in an environment with a lot of low- frequency noise

Question 17

Cochlea
* where located
* what filled with
* contains what structures

Answer 17

• located within the internal acoustic meatus
• filled with fluid that moves in response to vibrations, stimulating hair cells
• contains oval and round window and auditory vestibular nerve

Question 18

Auditory-Vestibular Nerve
* function
* what connect to

Answer 18

Carries signals for hearing and balance to the brain.

Connects the cochlea (hearing) and the vestibular system (balance) to the central nervous system.

Question 19

What is located at the base of the cochlea?

Answer 19

two membrane-covered openings: the oval window and the round window.

Question 20

Oval window
* what do
* where is it

Answer 20

• Transfers vibrations from the stapes which push on the oval window which initiates movement of the fluid inside the cochlea eventually leading to hearing
• found on cochlea behind stapes and above round window

Question 21

Round window
* what do
* where is it

Answer 21

Acts as a pressure release valve, allowing fluid movement inside the cochlea when the oval window is pushed inward.

• Positioned at the end of the scala tympani, a chamber of the cochlea.

Question 22

how do round and oval window work together

Answer 22

The oval window bulges inward when it transfers vibrations from the stapes, creating fluid movement in the cochlea that stimulates hair cells for hearing. The round window acts as a pressure release valve, bulging outward to allow proper fluid movement and prevent pressure buildup

oval window push fluid in - round window push it out

Question 23

Whats compression and rarefaction in the cochlea?

Answer 23

Compression (Pressure In) → At the oval window, where the stapes transmits sound vibrations.

Rarefaction (Pressure Out) → At the round window, which moves outward to relieve pressure.

Question 24

How is the cochlea organized?

Answer 24

1) basilar membrane
2) base
3) apex

Question 25

Basilar membrane * what 2 things does it do?

Answer 25

Separates the scala media (middle chamber) from the scala tympani. Vibrates in response to sound, activating hair cells.

Question 26

Base of cochlea * width and flexibility * location * frequency detection

Answer 26

* narrow and stiff * near oval and round windows and stapes * detect high frequency

Question 27

Apex of cochlea * width and flexibility * frequency detection * distance from windows

Answer 27

* wide and floppy * detects low frequencies * far from windows

Question 28

Scala vestibuli * top or bottom chamber? * contains what fluid * connected to what

Answer 28

* top chamber * periplymph fluid * connected to oval window

Question 29

Scala tympani * top or bottom chamber? * contains what fluid * connected to what

Answer 29

* bottom chamber * periplymph fluid * conncted to round window

Question 30

What is the helicotrema?

Answer 30

A small opening at the cochlear apex that connects the scala vestibuli and scala tympani. ensures both chambers are continuous with fluid

Question 31

Reissners membrane * where is * what do * why important that its FLEXIBLE

Answer 31

* inside cochlea * allows vibration of perilymph to also vibrate endolymph * important because the perilymph movement will cause the endolymph to move as well.

Question 32

Cochlear duct/Scala media: * where is it * what contain

Answer 32

* the middle chamber of the cochlea, located between the Scala Vestibuli (above) and the Scala Tympani (below) * contains the organ of Corti, endolymph, tectorial membrane, stria vascularis

Question 33

What is the stria vascularis * where is it

Answer 33

maintains the ionic balance of endolymph by pumping K⁺ into the endolymph by active transport * inside of Scala media

Question 34

What is the endolymph and what does it do

Answer 34

extracellular fluid with high potassium (K⁺) (150 mM) and low sodium (Na⁺) (1 mM). creates driving force for K+ to move into their hair cells

Question 35

How is the organ of corti structured?

Answer 35

It sits on the Basilar Membrane and is covered by the Tectorial Membrane. The reticular lamina is in the middle, holding onto the hair cells.

Question 36

What is the organ of corti

Answer 36

The Organ of Corti is the sensory structure inside the Scala Media (Cochlear Duct) responsible for converting sound vibrations into electrical signals.

Question 37

What is the tectorial membrane? What do?

Answer 37

A gel-like structure that sits above the hair cells. When sound vibrates the Basilar Membrane, hair cells push against the Tectorial Membrane, triggering electrical signals.

Question 38

What does the reticular lamina do

Answer 38

A middle structure that holds the hair cells in place.

Question 39

Inner hair cells: * function * how many arranged and how * efferent or afferent? * discuss hair bundles

Answer 39

* Send sound information to the brain. * 4500 form a single row * afferent (send info to brain) * Hair bundles are free to move

Question 40

Outer hair cells: * function * how many arranged and how * efferent or afferent? * discuss hair bundles

Answer 40

* Amplify sound and fine-tune hearing. * 12k - 20k arranged in 3 rows * efferent (receives input) * Hair bundles are embedded in the tectorial membrane

Question 41

Stereocilia * what is * what do

Answer 41

Hair-like Projections on Hair Cells Bending of stereocilia opens ion channels, allowing K+ and Ca²⁺ to enter, creating an electrical signal.

Question 42

What are Spiral Ganglion Cells and what do

Answer 42

Bipolar Neurons Carry signals from hair cells to the auditory nerve, then to the brain.

Question 43

purpose of modiolus?

Answer 43

use as a reference point for hair movement

Question 44

whats transduction by hair cells?

Answer 44

how hair cells in the cochlea convert mechanical vibrations into electrical signals

Question 45

whats a cochlear amplifier?

Answer 45

outer hair cells contain myosin and prestin which amplify sound by enhancing the movement of the basilar membrane. also about 1000 efferent fibers projecting from the brain stem toward the cochlea.

Question 46

What are tip links

Answer 46

Hair cells are connected by tip links (protein bridges) that ensure all the hairs move in the same direction.

Question 47

What happens when stereocillia bend towards tallest hair

Answer 47

When the stereocilia bend toward the tallest hair, the mechanically gated channels open, allowing K⁺ to enter from the endolymph (which is rich in K⁺).

Question 48

What happens when stereocillia bend away from tallest hair

Answer 48

If the stereocilia move away from the tallest hair, the channels close, preventing K⁺ entry. This results in hyperpolarization, slowing down or stopping neurotransmitter release.

Question 49

one spiral ganglion fiber receives input from HOW MANY inner hair cell

Answer 49

one spiral ganglion fiber receives input from only one inner hair cell

Question 50

one spiral ganglion fiber synapses with HOW MANY outer hair cells.

Answer 50

The situation is the opposite with outer hair cells. Because they outnumber their spiral ganglion cells, one spiral ganglion fiber synapses with numerous outer hair cells.