Final answer:
The pineal gland regulates physiological functions through melatonin production and is involved in the sleep-wake cycle and biological rhythms.
Step-by-step explanation:
The pineal gland, located in the epithalamus, is responsible for regulating several physiological functions through the production of melatonin. Melatonin is a hormone that controls the sleep-wake cycle and is involved in biological rhythms. It is also an antioxidant and has inhibitory effects on reproductive functions in some mammals.