Normally, most people sleep at night. What is the physiological rationale?

Question

Quizplus · Accepted Answer

The master biological clock in the suprachiasmatic nucleus (SCN) of the hypothalamus regulates sleep as well as other physiological processes. Darkness cues the clock for sleep. Light cues it for wakefulness. Light stimulates retinal messages. Histamine release is associated with wakefulness. Stimulation of the sympathetic nervous system promotes alertness.

Normally, Most People Sleep at Night