Human circadian rhythms Essay Example | Topics and Well Written Essays - 1500 words

Human circadian rhythms - Essay Example The circadian cycle includes 24 hrs of the day. A person usually sleeps approximately 8 hrs and is awake for 16 hrs. Throughout the wakeful hours, mental and physical functions are most active and growth increases but during sleep, voluntary muscle activities fade away and metabolic rate, respiration, heart rate, body temperature, and blood pressure are reduced. The actions of the digestive system rise during the resting period, the activity of the urinary system decreases. It is evident that hormones secreted by the body, such as the stimulant epinephrine (adrenaline), are released to its maximum just two hours before awakening to prepare the body for activity (Encyclopedia Britannica). Hypothalamus is the chief control centre especially the Suprachiasmatic nucleus (SCN), part of the hypothalamus; it receives signals about light and dark from the retina of the eye. Cyclical fluctuations of melatonin are essential for maintaining a normal circadian rhythm. Induction of sleep is gener ated when melatonin binds to receptors in the SCN (Encyclopedia Britannica). An understanding for the biological rhythms is fundamental part towards the perception of all aspects of life including death (Edery, 2000). Physiologic diurnal variation in cardiovascular system, heart rate and cardiac output plays an imperative role in finding the epidemiology of fatal cardiovascular events in the early hours of morning (Dunlap, 1999). It is manifested that diurnal variations are attributed to environmental stimuli or any kind of increase in sympathetic activity (Dunlap, 1999). It is evident that many features of cardiovascular physiology and pathophysiology involve alterations in the expression of genes regulating metabolic and contractile function of the heart and vasculature (Edery, 2000). In order to maintain homogeneous conditions of the body, all the biological processes must be maintained within physiologic boundaries. Failure to achieve a specific