Question
Biology Question on chemical coordination and integration
The hormone which regulates sleep-wake cycle in man is
A
Oxytocin
B
Melatonin
C
Thyroxine
D
Thyrocalcitonin
Answer
Melatonin
Explanation
Solution
Melatonin is a hormone produced by the pineal gland in darkness but not in bright light. Melatonin receptors in the brain, in a nucleus immediately above the optic chiasmata, react to this hormone and synchronize the nucleus to the 24-hour day/night rhythm, thus informing the brain when it is day and when it is night. Melatonin is a derivative of serotonin, with which it works to regulate the sleep cycle, and is being used experimentally to treat jet lag, SAD, and insomnia in shift workers and the elderly.