Lecture 11 - Hearing

Question 1

What are the 4 components involved in the hearing mechanism?

Answer 1

1. outer ear
2. middle ear
3. inner ear
4. central auditory nervous system

Question 2

Tympanic cavity

Answer 2

Small chamber, lying in the depth of the temporal bone, between the tympanic membrane and internal ear.

Question 3

Middle ear is composed of what three bones?

Answer 3

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

Question 4

Tympanic membrane

Answer 4

Thin membrane that forms the boundary between the outer and middle ear.

Vibrates in response to sound waves. Changes acoustical energy into mechanical energy.

Question 5

Organ of Corti (spiral organ)

Answer 5

Receptor organ for hearing in the cochlea.

Strip of hair cells allow for transduction of auditory signals into nerve impulses’ action potential.

Question 6

How does hearing work?

Answer 6

Sound waves enter the ear canal and vibrate against the tympanic membrane.

Sound passes through the tympanic membrane, vibrates the tiny bones of the ear, and is translated to a nerve impulse through the cochlea.

The cochlea sends sound impulses to the temporal lobe of the brain.

Question 7

Louder sound produces _______ pitch and _______ wave.

Answer 7

1. higher
2. shorter

Question 8

Frequency

Answer 8

How may waves are passing a point per second, the inverse of time.

Question 9

Wavelength

Answer 9

The length of those waves in meters, almost like a displacement.

Question 10

How do hair cells work?

Answer 10

Unlike many other electrically active cells, the hair cell itself does not fire an action potential.

Influx of positive ions from the endolymph depolarizes the hair cell, resulting in a receptor potential, opens voltage gated calcium channels.

Calcium ions then enter the cell and trigger release of neurotransmitters at the basal end of the cell and diffuse to nerve cells.

Question 11

Bundle of Vestibulocochlear nerve

Answer 11

Travels from cochlea through internal auditory meatus to skull cavity and brain stem.

Carry signals from cochlea to primary auditory cortex, with continuous processing along the way.

Question 12

Auditory Cortex

Answer 12

Wernicke’s Area within temporal lobe of the brain.

Sounds interpreted based on experience/association.

Question 13

Conduction deafness

Answer 13

Due to damage to the bones of the middle ear, usually with age.

Question 14

Nerve (transmission) deafness

Answer 14

Due to loss of hair cells, Organ of Corti and damage to auditory nerve.

Question 15

Some factors that can cause hearing loss?

Answer 15

1. Hereditary
2. Infections
3. Acoustic trauma (acute or chronic exposure to loud sounds; damages hair cells)
4. Rx drugs
5. Presbycusis (hearing loss of old age)