Chapter 13- Sensory systems (2)

Question 1

What is the bony labyrinth and where is it found?

Answer 1

It is a hollow cavity which is found in the inner ear

Question 2

What is the inner ear/ bony labyrinth filled with?

Answer 2

Perilymph suspended in a membranous labyrinth containing endolymph.

Question 3

What is endolymph?

Answer 3

A fluid rich in potassium and low in sodium and calcium.

Question 4

What is perilymph?

Answer 4

A fluid rich in sodium and low in potassium and calcium.

Question 5

The inner ear has three main structural components:

Answer 5

1- The cochlea
2- The vestibule
3- The semi-circular canals

Question 6

What is the structure of the cochlea?

Answer 6

The cochlea is divided by membranes into an upper chamber (scala vestibule) and a lower chamber (scala tympani), which join at the helicotrema.

Between them is the central cochlear duct (scala media)

Question 7

What are the Scala vestibule and tympani filled with?

Answer 7

Perilymph (sodium)

Question 8

What is the Scala media filled with?

Answer 8

Endolymph (potassium)

Question 9

What happens when the stapes is pushed in?

Answer 9

It causes the movement of perilymph in the scala vestibule, which is transferred along to the scula tympani, and causes the round window to bulge out.

Question 10

What are stapes?

Answer 10

Tiny bone in the middle ear and the one closest to the inner ear.

Question 11

Movement of the perilymph in turn causes movement of what?

Answer 11

The basilar membrane- the basement membrane that divides the scala media from the scala tempani.

Question 12

What sits on top of the basilar membrane?

Answer 12

Organ of Corti

Question 13

What resides at the organ of Corti?

Answer 13

The auditory receptor cells

Question 14

What are the sensory receptors in hearing called?

Answer 14

Hair cells

Question 15

What is the structure of hair cells?

Answer 15

They are modified epithelial cells that contain stereocilia which is the same as cilia.

The base of the hair cell is connected to a sensory neuron.

Question 16

What is the structure of the organ of Corti?

Answer 16

The organ of Corti consists of 4 rows of hair cells resting on the basilar membrane.

There is 1 row of inner hair cells and 3 rows of outer hair cells.

Question 17

What row of the organ of Corti are actual sensory receptors?

Answer 17

Only the single row of inner hair cells

Question 18

What are the role of the outer hair cells in the organ of Corti?

Answer 18

To amplify and regulate the mechanical motion of the basilar membrane.

Question 19

The stereocilia on the surface of the hair cells are embedded in what membrane?

Answer 19

The tectorial membrane.

Question 20

What happens to the stereocillia of the hair cells when the tectorial membrane is at rest?

Answer 20

The stereocilia of the hair cells are unbent.

Question 21

What happens when the basilar membrane rises?

Answer 21

The stereocilia will be bent against the mass of the tectorial membrane.

Question 22

What happens when the basilar membrane falls?

Answer 22

The stereocilia will be bent in the opposite direction.

Question 23

Bending of the stereocillia causes what to happen?

Answer 23

Gated potassium ion channels to open or close.

Question 24

If the stereocillia are bent towards the kinocilium, what happens?

Answer 24

Potassium channels open and the receptor cell depolarises, and the firing rate of the sensory neuron increases.

Question 25

If the stereocillia are bent away from the kinocillium, what happens?

Answer 25

Potassium channels close and the receptor cell hyperpolarises, and the firing rate of the associated sensory neuron decreases.