The Human Body Clock

The Circadian Rhythms Most people call it the annoyance of modern life. It can be a case of stress or fatigue or it can simply be a desynchronization of the body clock. The biological clock of the human body goes through many physiological, biochemical and behavioral processes in a day. This is called the Circadian rhythm of the body. These rhythms are in built and self sustained in the body and they can be adjusted to the environment through the external cues received like daylight. The circadian rhythms allow humans to anticipate and prepare for environmental changes that occur on regular intervals. They are basically associated to the outside world. These rhythms are important in regulating and coordinating the internal metabolic processes. Humans have a built in day that averages about 24 hours. The body clock resets itself daily to the 24 hour cycle The timing of a circadian rhythm is measured by the following factors: - Melatonin! secretion (produced by the pineal gland - Body temperature - Cortisol plasma level (produced by the adrenal gland) Circadian rhythms can be found in many organs and cell of the human body outside the suprachiasmatic nuclei (SCN) which is also called the master clock of the body. These are usually found in lungs, liver, pancreas, oesophagus, spleen, thymus and skin. They respond to light which plays a role in resetting the biological clock of the body. The light intensity and wavelength can alter the body clock. Daylight is specially known to have produced prominent effects on the circadian rhythms which can consequently effect the performance of an individual as well. The Role of Melatonin A key factor in humans getting their sleep is the exposure to darkness and light. The light stimulates a nerve in the brain called the hypothala-mus (SCN) which initiates signals to other parts of the brain that functions to make us feel sleepy and wide awake. When the eye is exposed to light at the start of the day this nerve starts functioning and resets the body clock. It delays hormones like melatonin until the darkness arrives. Melatonin is a hormone associated with the human sleep-wake cycle. It is made naturally by the body through the pineal gland. This gland is located just above the center of the brain. It remains inactive during the day and gets active when the sun goes down. When darkness occurs the pineal gland actively starts producing melatonin which is then released into the blood. When a person feels less alert it is because of the rise of this melatonin level in the blood. This level stays active for about 12 hours under normal conditions in the human body. The level starts decreasing as the body is exposed to sunlight. During the daytime this melatonin level is hardly detectable. Melatonin is also sometimes called the ‘Dracula of Hormones’. The bright light is also known to have a direct impact on melatonin by inhibiting the release of the hormone. It is not necessary that the pineal gland will produce melatonin under all circumstances. If the pineal gland is activated it will only produce melatonin if a person is in a dimly lit environment. Artificial indoor lightning can also prevent the release of melatonin. The amount of melatonin that is released varies from individual to individual. It is also related to age. Children tend to secrete more melatonin than adults. As they grow these levels start decreasing. Some studies have also shown that older people with sleeping problems not necessarily have lower melatonin levels as compared to people with normal sleeping routine