EduNinja• Explain the pupil reflex, limited to changes in light intensity and pupil diameter
The eye also controls the amount of light that enters the pupil.
Fig. 1.3 shows an eye in low light and in bright light.
Fig. 1.3
Describe the changes that occur in the eye when the light becomes bright, as shown in Fig. 1.3.
The diagram shows the appearance of the iris and pupil in three different light conditions.
Which row shows the size of the pupil of the eye in each light condition?
no
light
moderate
light
bright
light
1
2
3
1
3
2
2
1
3
3
2
1
A person moves from bright light into a dark room.
What changes occur in their eyes?
pupil
radial muscles
circular muscles
constricts
contract
relax
constricts
relax
contract
dilates
contract
relax
dilates
relax
contract
Which row shows the pupil reflex in bright light?
circular
radial
contracts
relaxes
larger
contracts
relaxes
smaller
relaxes
contracts
larger
relaxes
contracts
smaller
Involuntary actions occur because nerve impulses travel along the components of reflex arcs.
An example of an involuntary action is the rapid movement of a hand after unexpectedly touching a very hot object.
Fig. 4.1 shows the structures that are involved in the movement of the hand.
State one example of a reflex action that occurs in the eye.