Final answer:
Melatonin is a hormone secreted by the pineal gland in response to darkness, regulating the sleep-wake cycle; it is inhibited by bright light exposure. Maintaining proper melatonin levels is crucial for healthful sleep patterns and normal circadian rhythm functioning.
Step-by-step explanation:
Melatonin and the Pineal Gland
Melatonin is naturally secreted by the pineal gland in response to darkness, which makes the statement (a. True). The secretion of melatonin is closely linked to light exposure. It is inhibited by brightness, so the answer to the question about what inhibits the production of melatonin is (b. exposure to bright light). The pineal gland, a crucial endocrine structure located in the brain, regulates the sleep-wake cycle by secreting melatonin. This secretion increases as light levels fall, particularly during the night, promoting drowsiness and helping to regulate circadian rhythms. Conversely, exposure to light sends signals through the retinas and the suprachiasmatic nucleus to the pineal gland, reducing melatonin production and promoting wakefulness.
Because melatonin levels are influenced by the light-dark cycle, it is important to avoid bright light exposure during the middle of your sleep cycle, as this could decrease melatonin production and disrupt sleep. Additionally, melatonin has functions beyond sleep regulation, such as acting as an antioxidant and influencing reproductive functions and biological rhythms.