____ regulates circadian rhythms.

A) Thymosin
B) Melatonin
C) Erythropoietin
D) Atrial natriuretic peptide
E) Cortisol

Circadian Rhythms

Natural, internal processes that regulate the sleep-wake cycle and repeat roughly every 24 hours.

Melatonin

A hormone produced by the pineal gland that regulates sleep-wake cycles.

Cortisol

A steroid hormone released by the adrenal glands in response to stress or low blood-glucose concentration; plays a significant role in the body's response to stress.