Final answer:
The pineal gland secretes melatonin in the absence of light to regulate circadian rhythms and control the sleep-wake cycle. Light exposure inhibits melatonin production, which can disturb sleep patterns.
Step-by-step explanation:
To regulate our daily circadian rhythms, the pineal gland secretes melatonin in the absence of light. This tiny endocrine gland is located near the center of the brain and plays a critical role in controlling the sleep-wake cycle. The production of melatonin increases in response to darkness to promote drowsiness and is inhibited by light to aid wakefulness.
Cells in the retina detect light and transmit signals to the suprachiasmatic nucleus (SCN) in the brain, which then sends signals to the pineal gland to modulate melatonin secretion. This complex process is integral for maintaining our biological rhythms and enabling our bodies to adapt to the natural light-dark cycle of our environment. Therefore, engaging in activities that introduce light, such as using electronic devices with screens, can disrupt melatonin production and consequently disturb sleep patterns.