Topic 5- Homeostasis- The Eye

Question 1

Description of the eye

Answer 1

The eye is a sense organ that contains receptors sensitive to light intensity and colour.

Question 2

The Cornea

Answer 2

Transparent lens

Refracts (bends) light as it enters the eye

Question 3

Iris

Answer 3

Controls how much light enters pupil

Question 4

Pupil

Answer 4

Hole that allows light to enter the eye

Question 5

Lens

Answer 5

Transparent disc

Changes shape to focus light onto the retina

Question 6

Retina

Answer 6

Contains receptor cells rods and cones

Question 7

Rods

Answer 7

Rods in retina detect light intensity

Question 8

Cones

Answer 8

Cones in retina detect colour

Question 9

Optic nerve

Answer 9

Seneeiy neurone that carries electrical empulses between the eye and the brain

Question 10

Ciliary muscle

Answer 10

Muscle in shape of a ring around the eye.
It changes shape of the lens to when eyes focus on a near object.
Process is called accomodation

Question 11

Accomodation

Answer 11

When the ciliary muscles around eye contract to when eyes focus on an object’s that near

Question 12

The Pupil Reflex

Answer 12

It’s a reflex action to protect the eye from any damage caused by bright light and protect us from not seeing objects in dim lights
As it’s a reflex, it happens automatically

Question 13

Dim light:

Answer 13

Pupil dilates (widens) so more light enters the eye
Radial muscles contract
Circular muscles dilate

Question 14

Bright light:

Answer 14

Pupil constricts (becomes smaller/narrows) so less light enters the eye
Radial muscles relax
Circular muscles contract

Question 15

Close up objects:

Answer 15

Ciliary muscles contracts
Suspensory ligaments relax
Lens become thicker
Result: light is refracted more by lens to focus in near object

Question 16

Distant objects:

Answer 16

Ciliary muscles relax
Suspensory ligaments are pulled tight
Lens become thinner
Result: light is refracted less allowing the eye to focus on distant objects

Question 17

What are the two common defects if the eye

Answer 17

Myopia

Hyperopia

Question 18

What is Myopia and how is it treated?

Answer 18

Myopia is shirt sightedness:
The eyeball is too elongated
The lens are too thick and curved
The image is in focus in front if the retina
Treatment:
Concave lens corrects rays so that they can focus on the retina

Question 19

What is hyperopia amd how is it treated?

Answer 19

Hyperopia is long-sightedness:
The eyeball is too short
Therefore the image is brought into focus behind the retina
Treatment:
Convex lens refracts light rays so that they can focus on the retina

Question 20

Appart from slectacke lenses, what other treatments are available for both myopia and hyperopia?

Answer 20

Hard + Soft contact lenses
( Soft lenses have a higher risk of eye infections)
Laser surgery
(For myopia: the conrea isslimmed down, reducing refractive power)
(For hyperopia:the cornea shape is changed so that the refractive power increases)