Iris Reflex

Question 1

Iris Reflex

Answer 1

How the iris can change the size of the pupil - can control how much light can enter the eye

Question 2

How does the iris reflex work?

Answer 2

Uses circular and radial muscles that work antagonistically to either constrict (shrink) or dilate (expand) the pupil

Question 3

What happens in bright light?

Answer 3

Circular muscles: Contract
Radial muscles: relax
-> pupil is constricted (small)
-> helps reduce the amount of light entering the eye to avoid damage to retina

Question 4

What happens in dim light?

Answer 4

Circular muscles: relax
Radial muscles: contract
-> pupil is dilated (expanded)
-> Allows lots of light to fall on the retina to maximise vision