Ch.34 - The Senses

Question 1

Draw a vertical section of skin.

Answer 1

Diagram pg. 388

Question 2

Draw the structure of the eye.

Answer 2

Diagram pg. 390

Question 3

State the function of the conjunctiva.

Answer 3

The conjunctiva is a thin membrane protecting the sclera.

Question 4

State the function of the sclera (sclerotic coat).

Answer 4

The sclera is the white of the eye, it is opaque and it holds the eye in shape.

Question 5

State the function of the cornea.

Answer 5

The cornea is the transparent part of the eye, it lets light in and bends it toward the retina.

Question 6

State the function of the choroid.

Answer 6

The choroid nourished the eye with blood and contains melanin to absorb light. It ensures that no total internal reflection can occur.

Question 7

State the function of the retina.

Answer 7

The retina is the light sensitive screen at the back of the eye. It contains rods and cones.

Question 8

What are rods and cones?

Answer 8

Rods and cones are light receptors. There are far more rods than cones. Rods detect black and white. Cones detect colour. Rods re found all over the retina while cones are mainly found at the fovea.

Question 9

State the function of the fovea.

Answer 9

The fovea is the area of the retina containing only cones. It is the region of sharpest vision and images are focused at the fovea. Also known as the yellow spot.

Question 10

What is the blind spot?

Answer 10

The blind spot is a part of the retina with no receptors. Nerve fibres leave the eye through the blind spot.

Question 11

State the function of the optic nerve.

Answer 11

The optic nerve carries impulses from the rods and cones to the cerebrum.

Question 12

State the function of the lens.

Answer 12

The lens changes shape to focus light on the retina.

Question 13

How does the eye bring distant objects into focus? What is the power of accommodation?

Answer 13

Power of accommodation is the ability of the eye to focus a real image on the retina by changing its focal length using the ciliary muscles. The ciliary muscles can change the shape of the lens and thus change the power.

Question 14

What is the iris?

Answer 14

The iris controls the amount of light entering the eye by adjusting the size of the pupil. It gives the eye colour.

Question 15

What is the pupil?

Answer 15

The pupil is the hole at the centre of the iris. The pupil is black because no light emerges from the eye. The diameter of the pupil changes in bright and dark light by way of reflex action.

Question 16

What is the aqueous humour?

Answer 16

The aqueous humour is a salt solution that holds the eye in shape.

Question 17

What is the vitreous humour?

Answer 17

The vitreous humour is a viscous fluid that makes the eyeball turgid.

Question 18

How many muscles control the movement of the eye?

Answer 18

6

Question 19

What are the functions of the ear?

Answer 19

Hearing and balance.

Question 20

Draw a diagram of the structure of the ear.

Answer 20

Diagram pg. 392

Question 21

What is the pinna?

Answer 21

The pinna channels vibrations into the auditory canal. (It is made of cartilage).

Question 22

What is the auditory canal?

Answer 22

The auditory canal carries vibrations to the eardrums. Wax is secreted to trap dust particles and protect the ear.

Question 23

What is the eardrum?

Answer 23

The eardrum is a stretched membrane separating the outer and middle ear. It vibrates as a result of sound waves.

Question 24

What are the ossicles?

Answer 24

The ossicles consist of the hammer, anvil and stirrup. The stirrup is the smallest bone in the body. These transmit and amplify sound.

Question 25

What is the Eustachian tube?

Answer 25

The Eustachian tube runs from the middle ear to the pharynx and equalises pressure on either side of the eardrum.

Question 26

What is the cochlea?

Answer 26

The cochlea converts sound waves into electrical impulses to be sent down the cochlear (auditory) nerve.

Question 27

What is glue ear? How is it corrected?

Answer 27

Glue ear is caused by surplus fluid in the middle ear due to the blockage of the Eustachian tubes. The fluid inhibits the movement of the ossicles and the eardrum. It results in discomfort and partial deafness. It is corrected by nose drops or grommets. Grommets force fluid down the eustachian tube.