| BIOLOGICAL CLOCK |  Biological clocks help to keep our brains and bodies running on schedule. The body temperature, blood pressure, cardiovascular functions, activating the immunity system, bowl movement, sleep-wake cycle, hormone secretion, memory recall, jet lag, and many more functions are governed by the biological clocks. Scientists are trying to find answers to questions like, why time flies when we are having fun? Why life span is different for different species? The physiology of these timepieces is not completely understood. However, scientists are concluding that two types of clocks, ‘stop watch’ and ‘interval timer’ are located in our brain. The brain structures that are involved in this task consume more oxygen than those that are not involved. |
| |  Explanation
Daily cycles of light and dark influence many physiological processes, that operate on 24-hour cycles, will be most and least active. For example, the bowl movement, which starts in the morning at about 8 a.m, is suppressed during night at about 10:30 p.m. The brain tracks fluctuations in light with the help of ganglion cells in the retina of the eye. A pigment in some of the cells – melanospin – probably detects light, leading the retinal ganglion cells to send information about its brightness and duration to the suprachiasmatic nucleus (SCN) of the brain. Then the SCN dispatches the information to the parts of the brain and body that control circadian processes. Scientists believe that the events leading the pineal gland to secrete melatonin, sometimes called the sleep hormone. In response to daylight, the SCN emits signals that stop another brain region – the paraventricular nucleus – from producing a message that would ultimately result in melatonins’ release. After dark, however, the SCN releases the brake, allowing the paraventricular nucleus to relay a signal to secrete melatonin through neurons in the upper spine and the neck to the pineal gland. |  |
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