Question

Hank Greene, an airline pilot, is having difficulty with the sleep-wakefulness portions of his circadian cycle. The pineal gland secretes the hormone ___, which influences this cycle.

Answer 1

Melatonin

Step-by-step explanation:

Pineal gland is a tiny endocrine gland located in the brain. It secretes Melatonin which is released into the bloodstream. Melatonin is a hormone that regulates the body's daily (circadian) clock and is commonly used in human research to understand the body's biological time. There is a rhythm to the biology of the pineal gland. Melatonin is secreted according to the amount of light a person is exposed to. It varies based on changes in day length. Thus, referred to as both an endocrine clock.