The pineal gland releases this hormone, which is associated with circadian rhythms. a) Adrenaline b) Estrogen c) Melatonin d) Steroids
The correct answer and explanation is:
Correct Answer: c) Melatonin
Explanation (Approx. 300 words):
The pineal gland is a small, pea-shaped endocrine gland located near the center of the brain, between the two hemispheres, in a groove where the two halves of the thalamus join. Despite its small size, it plays a crucial role in regulating biological rhythms, especially the circadian rhythm, which governs the sleep-wake cycle.
The pineal gland primarily releases melatonin, a hormone that is strongly linked to the body’s internal clock. Melatonin production is influenced by light exposure. During the day, when light enters the eyes, signals are sent to the brain to inhibit melatonin secretion. At night or in darkness, the pineal gland is stimulated to produce and release melatonin into the bloodstream. This rise in melatonin levels makes us feel sleepy and helps regulate the timing of sleep.
Melatonin’s role in circadian rhythms helps synchronize our biological functions with the external environment, such as light and darkness. This synchronization is essential not just for sleep, but also for regulating body temperature, hormone secretion, and metabolic processes.
Melatonin is also involved in other physiological functions such as modulating immune responses and acting as an antioxidant. It can also influence reproductive hormones and cycles in some animals, though this is less significant in humans.
To clarify the incorrect options:
- Adrenaline is produced by the adrenal glands and is involved in the “fight or flight” response.
- Estrogen is a sex hormone primarily produced by the ovaries and is responsible for the development of female secondary sexual characteristics.
- Steroids are a broad class of compounds; some are hormones, like cortisol or testosterone, but they are not specifically linked to the pineal gland or circadian rhythms.
Therefore, the correct and most specific answer is melatonin.