Question

Fill in the blanks:
Sympathetic nerves __ the pupil while parasympathetic nerves ___ it.

• A. dilates
• B. constricts

Answer 1

Autonomic nervous system (ANS)

1. The ANS is present as pair of ganglia chains on both sides of the vertebral column. These ganglia are in close proximity to the organs under their control. It receives orders from the medulla, thereby controlling vital functions of the body.
2. The ANS controls the involuntary actions of glands, smooth muscles, and internal organs when we are awake and asleep.

Functions of the ANS

1. Various functions like digestion, circulation, heartbeat, respiration, blood pressure, etc. are controlled by two antagonistic systems of the ANS- the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS).
2. The size of the pupil changes according to the intensity of the light in order to help in better vision. The SNS prepares the body for action whereas the PNS prepares the body for relaxation. The SNS causes the pupil to dilate whereas the PNS causes the pupil to constrict.

Final answer

Sympathetic nerves dilate the pupil while parasympathetic nerves constrict it.