Lecture 10 - The Inner Ear and Balance

Question 1

What are the structures of the outer ear?

Answer 1

Auricle (pinna) and external auditory canal

Question 2

Function of the auricle (pinna)?

Answer 2

Gathers sound waves, aids in localization, amplifies sound

Question 3

External auditory canal

Answer 3

Allows air to warm before reaching tympanic membrane (TM).

Isolates TM from physical damage. Cerumen glands moisten/soften skin.

Question 4

Tympanic cavity

Answer 4

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

Question 5

In front, through the ___________, the tympanic cavity communicates with the _________.

Answer 5

1. Eustachian tube
2. nasopharynx

Question 6

Behind, through the entrance into the mastoid antrum, communicates with the latter and the cells of the ________.

Answer 6

mastoid process

Question 7

What are the parts of the inner ear?

Answer 7

Boney portion (bony labyrinth)
Membranous portion (membranous labyrinth)

Question 8

Membranous labyrinth is filled with fluid, known as _________ and is separated from the bony labyrinth by a fluid called ________.

Answer 8

1. endolymph
2. perilymph

Question 9

What does the membranous labyrinth consist of?

Answer 9

1. Three semicircular canals
2. Two otolith organs
3. Cochlea

Question 10

What are the 3 semicircular canals?

Answer 10

1. Horizontal (lateral)
2. Anterior (superior)
3. Posterior (inferior)

Question 11

What are the 2 otolith organs?

Answer 11

Saccule and utricle

Question 12

Function of the 3 semicircular canals?

Answer 12

Detect angular/rotary acceleration and deceleration of the head.

Question 13

Function of the 2 otolith organs (utricle and saccule)?

Answer 13

Detect linear acceleration and deceleration, and static tilt of the head.

Question 14

Function of vestibular nerve fibers?

Answer 14

Synapse with hair cells.

Question 15

Endolymph flows within the __________.

Answer 15

membranous labyrinth

Question 16

Perilymph flows between the _____________.

Answer 16

bony labyrinth and the membranous labyrinth

Question 17

The ionic composition of perilymph is similar to that of blood plasma and cerebrospinal fluid. The major cation is _______.

Answer 17

Na+

Question 18

Endolymph has a unique ionic composition, featuring a high concentration of _______ ions, which is unique among extracellular fluids.

Answer 18

K+

Question 19

The presence of K+ ions in the extracellular fluid creates a greater electrical potential, making the hair cells ___________.

Answer 19

much easier to depolarize to generate action potentials

Question 20

Crista ampullaris

Answer 20

Sense organ in the semicircular canal.

Question 21

in each ampulla of the semicircular canals, there is a ________ whose cilia project into gelatinous mass called a cupula.

Answer 21

crest of hair cells

Question 22

Cupula

Answer 22

Gelatinous mass

Question 23

Otoliths

Answer 23

Calcium carbonate crystals

Question 24

The cilia from all hair cells project into a gelatinous mass. Displacement of the mass in a given direction causes all the hair cells to ________.

Answer 24

bend in that direction

Question 25

Hair cells are the sensory receptors of both ___________.

Answer 25

auditory system and vestibular system.

Question 26

Utricle and saccule each contain a _______, which transduces _________.

Answer 26

1. macule
2. static head tilt, linear acceleration and deceleration

Question 27

When rotation moves in one direction, bending of the cilia causes the hair cells to _________ and impulses reach the brain at a _________.

Answer 27

1. depolarize
2. faster rate

Question 28

In the utricle and saccule, the hair cell receptor is called the ______.

Answer 28

macula

Question 29

Both the utricle and saccule respond to acceleration. The utricle responds to ____________ acceleration and saccule responds to _____________ acceleration.

Answer 29

1. horizontal
2. vertical

Question 30

Acceleration in a given direction results in bending of the hair cell cilia in the __________.

Answer 30

opposite direction

Question 31

Vestibular reflexes coordinate ___________ movements.

Answer 31

eye and head

Question 32

Vestibular Ocular Reflex (VOR)

Answer 32

When rotation starts, eyes move slowly in the direction opposite the rotation, maintaining visual fixation.

Question 33

The eyes are controlled by what three pairs of muscles?

Answer 33

1. medial/lateral rectus
2. superior/inferior rectus
3. inferior/superior oblique