Final answer:
Pinealocytes in the pineal gland produce melatonin, which is involved in regulating biological rhythms, such as the sleep-wake cycle. Its production increases at night and is reduced by bright light exposure.
Step-by-step explanation:
Pinealocytes are specialized cells within the pineal gland that are responsible for the production of the hormone melatonin. Melatonin is known to affect biological rhythms, such as the sleep-wake cycle and eating habits, and has an influence on reproductive functions in some mammals. It is also a potent antioxidant, protecting the central nervous system from harmful free radicals. The production of melatonin is known to increase during the night and decrease during exposure to bright light.