Lecture 9: Auditory Senses

Question 1

List the bones of the middle ear in order

Answer 1

Malleus, Incus, Stapes

Question 2

Tensor tympani

Answer 2

Muscle that inserts on the malleus and pulls handle of malleus inward

Question 3

Stapedius

Answer 3

Muscle that inserts on the stapes and pulls stapes outward

Question 4

Attenuation reflex

Answer 4

Opposing forces of the tensor tympani and stapedius muscles that dampens sound; protects the cochlea and masks low frequency sounds in loud environements

Question 5

How does the action of the tensor tympani and stapedius muscles affect a person’s sensitivity to her/her own speech?

Answer 5

Decreases sensitivity to own voice

Question 6

What two structures are involved in impedance matching?

Answer 6

Tympanic membrane and ossicles

Question 7

Why is impedance matching important?

Answer 7

Increases force from the ossicular system to cochlear fluid which is needed in order to cause vibration in the fluid

Question 8

How is hearing affected in the absence of the ossicular system?

Answer 8

Sound still passes through the middle ear to cochlea, but sensitivity is decreased by 15-20 decibels

Question 9

What are the major components of the cochlea?

Answer 9

Scala vestibuli, Scala media, Scala tympani, Reissner’s membrane

Question 10

What is the function of Reissner’s membrane?

Answer 10

Separates scala media from scala vestibuli, maintaining special fluid (endolymph) within scala media

Question 11

Basilar membrane

Answer 11

Separates scala media from scala tympani; contains fibers that have the ability to vibrate

Question 12

How does the length and diameter of basilar fibers differ from the oval window to the apex of the cochlea?

A. Length and diameter increase from oval window to apex
B. Length and diameter decrease from oval window to apex
C. Length decreases from oval window to apex, while diameter increases
D. Length increases from oval window to apex, while diameter decreases

Answer 12

D. Length increases from oval window to apex, while diameter decreases

Question 13

What are the characteristics of fibers near the oval window and at what frequencies do they vibrate?

Answer 13

Stiff, short fibers; beat at high frequency

Question 14

What are the characteristics of fibers near the apex of the cochlea and at what frequencies do they vibrate?

Answer 14

Long, limber fibers; beat at low frequency

Question 15

What are the sensory receptors of the organ of Corti?

Answer 15

Hair cells

Question 16

What creates the mechanical transduction leading to the depolarization of the hair cell membrane?

Answer 16

Tensile force created on shorter cilia when they are bent in the direction of longer sterocilia

Question 17

Where is endolymph located and what is its ionic composition?

Answer 17

Scala media; high [K+], low [Na+]

Question 18

Where is perilymph located and what is its ionic composition?

Answer 18

Scala vestibuli and scala tympani; Low [K+], high [Na+]

Question 19

What is the endocochlear potential?

Answer 19

+80 mV difference between endolymph and perilymph

Question 20

Place principle

Answer 20

Nervous system detects sound frequencies by determining positions along the basilar membrane that are most stimulated

Question 21

How does the frequency range that can be heard change with age?

Answer 21

Frequency is shortened; age related hearing loss usually in high frequency sound

Question 22

Where does decussation occur between the right and left auditory pathways?

Answer 22

Brainstem/pons

Question 23

What is the difference between the primary auditory cortex and association areas?

Answer 23

Auditory cortex directly excited by projections from medial geniculate body; association areas are secondarily excited by impulses from auditory cortex