Why is your pupil so sensitive?

The pupil is the black circular opening in the center of the eye that allows light to enter the eye. It is controlled by the iris, which is the colored part of the eye. The pupil dilates (gets larger) in low-light conditions to allow more light to enter the eye, and constricts (gets smaller) in bright-light conditions to protect the retina from damage.

The pupil is very sensitive to changes in light levels because it is controlled by the autonomic nervous system, which is responsible for regulating involuntary bodily functions. The autonomic nervous system is constantly monitoring the environment and adjusting the pupil size accordingly.

When the light levels are low, the autonomic nervous system sends signals to the iris to dilate the pupil. This allows more light to enter the eye, which helps us to see better in low-light conditions. When the light levels are high, the autonomic nervous system sends signals to the iris to constrict the pupil. This protects the retina from damage by reducing the amount of light that enters the eye.

The pupil is also sensitive to other stimuli, such as drugs, alcohol, and certain medical conditions. For example, some drugs, such as marijuana and cocaine, can cause the pupils to dilate. Alcohol can also cause the pupils to dilate, but this effect is usually temporary. Certain medical conditions, such as Horner's syndrome and Adie's tonic pupil, can also cause the pupils to become dilated or constricted.