Which gland secretes melatonin, influencing circadian rhythms?

The pineal body, also known as the pineal gland, is responsible for secreting melatonin, a hormone that plays a critical role in regulating circadian rhythms, which are the physical, mental, and behavioral changes that follow a daily cycle. This gland is located deep within the brain and is stimulated by darkness, leading to an increase in melatonin production, which helps to signal the body that it is time to sleep. Conversely, exposure to light inhibits melatonin secretion, encouraging wakefulness. This regulation of sleep-wake cycles is essential for maintaining various physiological processes in animals, including mood, sleep patterns, and reproductive functions. Understanding the function of the pineal body in melatonin production is pivotal for those studying anatomy and physiology, especially in relation to the endocrine system and its impact on behavior and health.