The primary reason for this is the human body’s nervous system. The brain and the spinal cord are in the centre and together constitute the Central Nervous System (CNS). All the nerves spreading out from these to innervate the peripheries are called the Peripheral Nervous System (PNS). As soon as we get hurt, our brain processes it as an emergency. As a result, an automatic system is activated that incites an involuntary response in our body, resulting in the dilation of the pupil. With excessive amount of light entering the pupil, it becomes momentarily blinding and the eyes shut on their own.
Why do our eyes shut when we feel extreme pain?
