Final answer:
Melatonin is the hormone responsible for regulating sleep-wake patterns and circadian rhythms. It's secreted by the pineal gland and its production is influenced by light exposure, with darkness increasing and light decreasing its secretion.
Step-by-step explanation:
The hormone that affects our sleep-wake patterns and maintains our biological cycles is melatonin. This hormone is secreted by the pineal gland, which is an endocrine structure in the brain. Melatonin plays a crucial role in regulating our circadian rhythms, which are the natural cycles that tell our bodies when to sleep, wake and eat, as well as playing a part in immune function during sleep. The secretion of melatonin is stimulated by darkness and is inhibited by light, aligning our sleep-wake cycles with the outside environment. At night, as light levels decrease, melatonin production ramps up causing us to feel drowsy, while during daylight, the production is suppressed, contributing to alertness. Such precise regulation helps maintain optimal health and function.
In addition to the pineal gland's role, the hypothalamus contains a specific area known as the suprachiasmatic nucleus (SCN) which is involved in the control of circadian rhythms and acts as the 'biological clock' of the body. It processes signals regarding light levels received through the eyes that influence melatonin production. Therefore, exposure to light at night, such as from electronic screens, can disrupt the natural production of melatonin and might lead to sleep disturbances.