Humans are programed to respond to the rhythms of the daily light-dark cycles. There are also internal biological clocks that sustain the internal physiological processes and which are connected to the daily light and dark cycles. The internal circadian pacemaker (biological clock) sets the tone for the circadian rhythm. It is responsible for the responses to the 24-hour solar cycle which in turn determines our timed daily activities like food intake, sleep, and social cues.
Any disruption in these routines leads to increased risks in health, productivity, and susceptibility to sickness and disease; depression, high blood pressure, cancer, sleep disorder and various metabolic disorders. Certain physiological processes like hormone secretion, body temperature etc. functions are normal to healthy individuals but have been shown to loose normal function in patients with disorders in connection with disruption of the circadian rhythms.
Some biologists have observed that cell division heightens at certain times of the day. The cells of the mouth divide before night fall. The living cells to are vulnerable to unfavorable modifications by UV during the day and this gives a special advantage over those that divide in the night.
There are blue-light-absorbing flavoproteins connected with the circadian rhythmic function in invertebrates. They use photon energy to repair DNA and reset the circadian clock. Photoreceptors in the mammalian retina are able to convert electromagnetic radiation from the sun into internal signals leading to light sensitivity that controls the rise and bedtime awareness in humans. The amazing jet lag experience results from travel to a new time zone and has been attributed to time irregularities between the biological rhythm and the local solar time. Normal rhythm is reset in a short period of time following the rising and setting of the sun which resets the biological clock.
The workings of the hepatic, intestinal, and renal organs that detoxifies and sustains the internal systems are regulated in a circadian manner. It provides the molecular basis for why drug therapy is dependent on dosing time. This has provided cues for the development and design of chronotherapeutics (biological clock-dependent drug therapy). Certain diseases like heart attacks and strokes occur most commonly early in the morning when blood pressure is at its peak. When the circadian genes are turned off, cells multiply indefinitely – become cancerous. That’s because there is loss of timing and control. Chronotherapeutic diseases also include asthma, cardiovascular diseases, glaucoma, and rheumatoid arthritis. In order to treat these diseases, numerous chronotherapeutic drug delivery systems have been developed, such that drug is released in the period when it is most needed.
Scientists have arrived at a conclusion after several experiments in animals and in humans which clearly demonstrate that all organisms are highly organized according to circadian rhythms. Concomitantly, circadian rhythms have been found to alter the body and mind performance in humans, the susceptibility to disease and the general biochemistry of the body. Optimization of the effectiveness of daily routine could not be achieved without taking into account the timing of the rhythms. Knowing about the workings of our internal clock is essential to avoid disruptions which are known to have clinical implications. At some point in time, it could be possible to use certain drugs or vitamins to reset individual peripheral circadian clocks in the organs or even to reset one or more and leave the others alone. That might help modulate the pathological and physiological balance of our internal systems with hope of improved medical therapies and general health.