Question

What happens when the human comes in bright light?

• A. Synthesis of rhodopsin
• B. Mydriasis
• C. Miosis
• D. None of the above

Answer 1

Answer: (C)

Miosis

When bright light is shown on the eye, light-sensitive cells in the retina, including rod and cone photoreceptors and melanopsin ganglion cells, will send signals to the oculomotor nerve, specifically the parasympathetic part coming from the Edinger-Westphal nucleus, which terminates on the circular iris sphincter muscle. When this muscle contracts, it reduces the size of the pupil. This is the pupillary light reflex, which is an important test of brainstem function. Another term for the constriction of the pupil is miosis. Substances that cause miosis are described as miotic.