Circadian Rhythm Essays

Circadian Rhythm Essays Circadian Rhythm Paper Circadian Rhythm Paper Circadian Rhythm As Wikipedia defined it, circadian rhythm is a 24-hour cycle which is involved in physiological processes of living beings such as plants, animals, fungi and cyanobacteria. Circadian literally means about a day; the words originated from the the latin terms â€Å"circa† (around) and â€Å"dies† (day).   From Howard Hughes Lecture (HHL) 0 in circadian time tells the beginning of a subjective day, and 12 is the beginning of a subjective night. From the report of Harvard Feature Science (HFS) jet lag is a common experience for people travelling by airplane, aside from sleepiness other symptoms are also exhibited due to change. Another, people having night shift at work when forced to wake up early might experience nausea or muscle fatigue due to change in their circadian rhythm. The circadian clock of mammals is consist of   10,000 clock cells in the hypothalamus called the suprachiasmatic nucleus, or SCN In recent studies conducted by Physiological Genomics (PG), it showed that clock cells also reside in other tissues of the body as well. A time indicator such as morning light strikes retina, the photic input is passed on to SCN and carried on to other clock cells in the body. If external time signals change (i.e. time zones), the clock cells of SCN and the other clock cells in the body must conform with the change and resynchronize to the rest of the body. Day and night cycles are most studied by our scientists since almost all species exhibit daily changes in their behavior and/or physiology. These daily rhythms are not simple responses to the changes occurring within the day simply a response to the 24-hour changes. Organisms can do in advance and get ready for the changes within the physical environment ensuring that organisms will do the right thing because of their biological clock or timekeeping system. The biological clock ensures synchronization among internal temporal components of the body.The synchronization of the external and internal environments is vital for an organism’s survival. If synchronization is not attained between external and internal environments, it can result to the   individual’s immediate demise (Vitaterna and Takahashi 85). Biological clocks are very important for all living creatures particularly humans but still the processes involved   in biological timekeeping systems and the potential consequences of its failure needs to be settled. Chronobiology is a field focusing on biological timing, including high frequency cycles (e.g., hormone secretion occurring in distinct pulses throughout the day), daily cycles (e.g., activity and rest cycles), and monthly and daily cycles (Aschoff 11) .The study about biological clocks started 5 decades ago. The area of sleep research, which is also under the field of chronobiology, evolved independently upon the identification of various sleep stages (Dement 25). Due to these stages, it branched out and resulted to further important studies like the system controlling the patterns of sleep – circadian rhythm (timekeeping system of humans) Free-running circadian rhythms are those that can de expressed even in the absence of a 24-hour signal from the external environment; it is not synchronized by any cyclic change in the physical environment. A diurnal rhythm cannot be called circadian until it has been shown to carry on under constant environmental conditions and can be set apart from other rhythms which are just responses from the 24-hour environmental changes. A rhythm which continuously works in the absence of a dark-light cycle or other exogenous time signal (i.e., a Zeitgeber) indicates the existence of internal biological clock. The persistence of rhythmicity does not necessarily rule out the presence of other uncontrolled cycles generated by the Earths revolution on its axis might be driving the rhythm (Aschoff 49). Circadian rhythms are produced at the cellular level, because the rhythms of unicellular organisms are the same as rhythms of highly complex mammals which suggests that cycle of expression is controlled by genes responsible for the timekeeping mechanism of the clock. Circadian cycles works for almost 24 hours but not exactly 24 hours. A 24-hour cycle deviation allows the internal timekeeping system to be synchronized with the light-dark environments. The deviation increases the precision of the cycle in controlling time. Circadian rhythms can be synchronized, or entrained, by external time cues, such as the light-dark cycle. It also has the ability to work properly even in the absence of external time cues (meaning that they are not driven by the environment). If a change has occurred within the external cues, rhythms will automatically align with the new cues (Pittendrigh 170). The process of automatic aligning of the system with the changes in its cues is still studied if this automatic aligning is attained by lengthening or shortening the cycle until it is aligned to the new cues and revert to the original length or aligning with the new cues can be achieved by discrete resetting events. Various experiments are done to come up with a good deal of answers and it was discovered that the organisms have different response to light depending on the phase of their cycle if it’s unchanged, delayed or advanced In addition to the timing of the light exposure, the intensity of light can alter cycling periods if organisms are exposed in constant light; longer contact of an organism to brighter light intensities can lengthen the period in some species and shorten it in other species, it depends (Stokkan and Yamazaki   492). Other factorssuch as social interactions, activity or exercise, and even temperaturealso can modulate a cycles phase. Temperature’s influence on circadian rhythms is also important since change in temperature can affect the cycle’s phase without directly affecting the pace of cycling; the cycle can begin at an earlier or later-than-normal time ending up on its usual length. Also, this ability of the internal clocks pacemaker to make up for changes in temperature is critical to its ability to predict and adapt to environmental changes, because a clock speeding up and slowing down as a response to temperature change is not useful at all (Aschoff 1427). The circadian pacemakers in higher organisms are situated in cells of specific structures of the organism. These structures include certain regions of the brain (i.e., the optic and cerebral lobes) in insects; the eyes in certain invertebrates and vertebrates; and the pineal gland, which is located within the brain, in nonmammalian vertebrates. In mammals, the circadian clock resides in two dusters of nerve cells called the suprachiasmatic nuclei (SCN), which are located in a region at the base of the brain called the anterior hypothalamus (Mistlberger and Bergmann 15). The task of the SCN is very crucial for the proper functioning of the system with regards to different organisms because damaging (i.e., lesioning) the SCN can lead to disruption and abolition of endocrine and behavioral circadian rhythms. SCNs as the major controller of pacemaker managing other rhythmic systems was confirmed by studying organisms such as rat and hamsters. SCN is confirmed as the primary site of regulation with regards to circadian rhythmicity in mammals and thus to further understand the 24-hour cycle, one must study SCN (Ralph   976). Lesions on the SCN have numerous effects on the rhythms but their effects on sleep are less clear. SCN lesions interrupt the consolidation and pattern of sleep in rats but nominal effects on the amount of sleep of other organism thus it was postulated that circadian clock adjusts an organism’s sleeping hours   and the existence of homeostatic control which is responsible for waking (sleep debt) (Mistlberger and Bergmann 17). IMPORTANCE OF THE CIRCADIAN CLOCK FOR HUMAN HEALTH AND WELL-BEING Almost all physiological and behavioral functions in humans are on a rhythmic basis often resulting to dramatic diurnal rhythms in human that can be a result of involuntary or voluntary circumstances disturbing the circadian rhythmicity. There are many adverse effects of disrupted circadian rhythmicity correlated with the upset sleep-wake cycle. Some rhythmic processes are more affected by the circadian dock than by the sleep-wake state, whereas other rhythms are more dependent on the sleep-wake state (Vitaterna and Turek 85). Humans are capable of overriding the biological clocks and their rhythmic outputs. If sleep-wake cycle is not in synchronized with the rhythms controlled by the circadian clock (e.g., during shift work or rapid travel across time zones), adverse effects may occur. Sleep disturbances are linked with jet lag or shift work and other unknown reasons which can be indicative of a mental and psychological disorder that can tap other form of illnesses. Often, other circadian rhythm abnormalities are associated with various disease states, although again the importance of these rhythm abnormalities in the development (i.e., etiology) of the disease remains unknown (Brunello 110). A circadian pattern among similar diseases or patient groups are tried to be plotted; for example, a circadian pattern showing that men are prone to death in the morning and if this rhythm is studied, patterns can be obtain which is very useful for man and his health (Proschan and Follman 717) Death and myocardial infarctions happen randomly throughout the 24-hour day but   often, it tend to cluster at   and these phenomena are known as circadian rhythms (Peters and Zoble 1000). The role of circadian abnormalities in various disease are still unknown; insufficient knowledge on how circadian signals from the SCN are relayed to target tissues. A better understanding of the nature of circadian signal output from the SCN to its target systems must be carefully studied. The two major causes of death namely heart attacks and strokesshow time-of-day variation in their occurrence is a case in point. The mechanisms responsible for the rhythmicity of these disorders must be identified and furthermore look for therapeutic ways to influence the rhythmicity of this events (Proschan and Follman 720). The time distribution of heart attacks is really undetermined but if the patterns of these attacks are known, it can be great aid for man. 31 patients who had a cardiac arrest were studied and the times of their attack were track down with the help of their family members who specified the time of their attacks, the attacks started at interval midnight-1 A.M (Maron and Kogan 250). The daily variation in body rhythms would not be enough in creating a drug treatment but sufficient knowledge of the effect of circadian rhythms can help doctors devise more effective ways of administering therapies (Willis 18). A sound sleep can be an effective treatment in fight against cancer. Psychosocial factors can affect behavior patterns like exercise, food and drink intake and the sleep-wake cycle can take effect in balancing the hormones inside body. The sleep/wake cycle, called the circadian rhythm is linked with persons social network to his or her cancer prognosis. The two ways in which the cir cadian rhythm can influence cancer progression is through a hormone called melatonin, which the brain churns out during sleep. Melatonin is an antioxidant that cleans up damaging free-radical compounds; if the circadian system is disrupted, it produces less melatonin making the body prone to cancer-causing mutations (Yapp 19). The interaction between drugs, including alcohol, and circadian rhythm is apparent in the temporal, or time-related, restraints on experimentation. Alcohol has profound effects on the circadian rhythms of mammals. Alcohol hang-over had been related to jet-lag-like circadian disruption (i.e., phase shifts) of the bodys normal rhythm (Gauvin and Baird 820).Alcohol consumption is directly related with internal jet lag resulting to phase shifts in the internal clock of the body. Alcohol consumption can cause disruption of circadian rhythm (Holloway and Miller 520). The bodys temperature rhythm in people is affected by their alcohol consumption. The body temperature reaches its peak during late afternoon and reaches its lowest point during early morning. Body temperature, alcohol and mammalian circadian rhythm are interrelated with each other and a change in one of these components will affect the other components. Alcohol and circadian rhythm can work together with temperature at both the cellular and behavioral levels. Alcohol-induced circadian rhythm disruption can eventually decrease the maximum ability performance of an individual. Circadian effects can cause dangers to both the affected person and other people. Circadian system and alcohol consumption must be further studied to provide foundation for pharmacological and behavioral advances in the treatment of alcohol abuse and addiction as well as assist in solving problems related to public safety (Gallaher and Egner 35). Alcohol exerts its effects both on body and brain. Alcohol-induced thermoregulation is responsible for the processing of incoming sensory signals (i.e., the anterior hypothalamic preoptic area, or AH/POA).   If not all, almost all nerve-cell-communication chemicals take part in alcohol-induced hypothermia (Crawshaw and Wallace 153). The shifts observed in an organisms normal circadian rhythm have been found to induce alcohol consumption. These shifts involve phase delays which occur at the peak of body rhythm temperature. Shifts in the amount of light and dark period during a 2-month period time have and adverse effects on alcohol intake; the photoperiod shifts acted as stressors resulting to disruption of the internal rhythm in the body (Gauvin and Baird 823). The brain does not directly respond to individual homeostatic fluctuations of, it acts as an overall regulator making sure that individuals can adapt to the changes that occurred in the environmental cycle. There is the indirect modulation, by way of alcohols disruptive effects on the hormonal and chemical communication networks which is involved in maintaining the temperature balance in the body (Holloway 94). The level of an individual’s arousal has a major effect on his or her performance in a number of areas, decline in arousal related with shift work has been found to impair performance on a variety of cognitive tasks (Chiles, Alluisi, Adams 145). Low arousal levels due to extended work shifts and sleep deprivation also decrease the maximum output of an individual (Caldwell, 200). In researches, energetic arousal reaches its peak around 11:30 am., whereas Thayer and Takahashi (17) found that this type of arousal reaches its peak at 1:19 p.m. Clements, Hafer, and Vermillion (388)   found the possibility that there are two peaks for energetic arousal, one around noon and the other in the early afternoon. Adan and Guardia (233) found circadian rhythms for both tense and energetic arousal are very different. The precise effects of low or high levels of arousal on performance have advantageous benefits in different areas. Redesigning of tasks and environment can be done to attain maximum performance. The fluctuations in arousal over the course of the workday are correlated with fluctuations in performance on a variety of task; performances are better in morning (Blake 345). Hormones are highly active in the morning; concentration and short-term memory are in their peak of performance and body temperature helps in maximizes muscle performance.   Better understanding of these circadian rhythms of arousal and their impact on task performance can help in achieving the optimum productivity (Yapp 19). Arousal increases readiness to respond to internal and external stimuli. Researches suggest the two distinct forms of arousal labeled as tense and energetic. Tense arousal is a continuum ranging from calmness to anxiety, and energetic arousal is a continuum ranging from tiredness to energy (Matthews, Jones, Chamberlain 40). There is an important evidence for the usefulness of dealing with arousal as multidimensional in nature. Energetic arousal is associated with better performance on tasks such as vigilance, visual search, and serial reaction time, whereas tense arousal does not seem to affect performance on these tasks (Matthews, Jones and Chamberlain 37). Tense arousal is common among college students from typical days to exam days than energetic arousal. The present studies want to know if breaking down energetic arousal into the dimensions of wakefulness and vigor can help in resolving issue about arousal and performance (Thayer 65). The body in rhythm is important in overall health. Human being takes their cues from the light and the dark but that biological clocks tick a bit longer than the standard, 24-hour day. The 24-hour cycle is used. When the light triggered the retina, the circadian clock is reset. Odd-shift workers have difficulty sleeping when their day is done even if physically exhausted since in this condition, the normal cycle is squeezed into an abnormal environment; getting out of ones circadian rhythm can result in slower reaction times and other symptoms common to sleep deprivation (Toto 1). References Adan, A., Guardia, J. (1993). Circadian variations of self-reported activation: A multidimensional approach. Chronobiologia, 20, 233-244. Aschoff, J. (1960). Exogenous and endogenous components in circadian rhythms. Cold Spring Harbor Symposia on Quantitative Biology, 25. Biological Clocks. New York: Cold Spring Harbor Press, 1960. Aschoff, J. (1962). Circadian rhythms in man. Science. 148, 1427-1432. Blake, M. J. F. (1967). Time of day effects on performance in a range of tasks. Psychonomic Science, 9, 345-350. Brunello, N., Armitage, R., Feinberg, L. et al. (2000). Depression and sleep disorders: Clinical relevance, economic burden and pharmacological treatment. Neuropsychobiology. 42, 107-119. Caldwell, J. (1995). Assessing the impact of stressors on performance: Observations on levels of analyses. Biological Psychology, 40, 197-208. Chiles, W. D., Alluisi, E. A., Adams, O. S. (1968). Work schedules and performance during confinement. Human Factors, 10, 143-196. Circadian Rhythm. Retrieved on December 1, 2006 http://en.wikipedia.org/wiki/Circadian_rhythm Clements, P. R., Hafer, M. D., Vermillion, M.E. (1976). Psychometric, diurnal, and electrophysiological correlates of activation. Journal of Personality and Social Psychology, 33, 387-394. Crawshaw, L., Wallace, H. Crabbe, J. (1998). Ethanol, body temperature and thermoregulation. Clinical and Experimental Pharmacology and Physiology. 25, 150-154 Dement, W.C. (2000). History of sleep physiology and medicine. In Kryer, M.H., Roth, T., Dement, W.C. (eds.). Principles and practice of sleep medicine (3rd edn.) Philadelphia: W.B. Saunders. Dickman, S.(2002). Human factors.   Human Factors and Ergonomics Society, 44(3), 429-433. Follman, D. Proschan, M. (1997). A restricted test of circadian rhythm. Journal of the American Statistical Association. 92 (438), 717 – 725. Gallaher, E., Egner, D. (1987). Rebound hyperthermia follows ethanol-induced hypothermia in rats. Psychopharmacology (Berlin), 91, 34-39. Gauvin, D., Baird, T.,Vanacek, S. et al. (1997a). Effects of time-of-day and photoperiod phase shifts on voluntary ethanol consumption in rats. Alcoholism: Clinical and Experimental Research, 21, 817-825. Holloway, F., Miller, J., King, D., Bedingfield, J. (1993). Delayed ethanol effects on physiological and behavioral indices in the rat. Alcohol. 10, 511-519. Maron, B. J., Kogan, J., Proschan, M. A., Hecht, G. M., and Roberts, W. C. (1994). Circadian variability in the occurrence of sudden cardiac death in patients with hypertrophic   cardiomyopathy. Journal of the American College of Cardiology, 77, 251-261. Matthews, G., Jones, D. M., Chamberlain, A. G. (1990). Refining the measurement of mood: The UWIST Mood Adjective Checklist†. British Journal of Psychology, 81, 17-42. Mistlberger, R.E., Bergmann, B.M. Rechtschaffen, A. (1987). Relationships among wake episode lengths, contiguous sleep episode lengths, and electroencephalographic delta waves in rats with suprachiasmatic nuclei lesions. Sleep 10.1 (1987):12-24. Muller, J. E., Ludmer, P. L., Willich, S. N., Tofler, G. H., Aylmer, G., Klangos, I., and Stone, P. H. (1987). Circadian variation in the frequency of sudden cardiac death. Circulation. 270, 2598-2601. Peters, R. W., Zoble, R. G., Liebson, P. R., Pawitan, Y., Brooks, M. M., Proschan, M. (1993). Identification of a secondary peak in myocardial infarction onset 11 to 12 hours after awakening: The cardiac arrhythmia suppression trial (CAST) experience. Journal of the American College of Cardiology, 22, 998-1003. Pittendrigh, C.S. (1960). Circadian rhythms and the circadian organization of living systems. Cold Spring Harbor Symposia on Quantitative Biology, 25. Biological Clocks. New York: Cold Spring Harbor Press. Ralph, M.R., Foster, R.G., Davis, F.C., Menaker, M. (1990). Transplanted suprachiasmatic nucleus determines circadian period. Science, 247, 975-978. Stokkan, K.A., Yamazaki, S., Te, H., Sakaki, Y. Menaker, M. (2001). Entrainment of the circadian clock in the liver by feeding. Science, 291, 490-493. Takahashi, J. Turek, F., and   Vitaterna, M. (2001). Overview of circadian rhythm. Alcohol Research Health, 25.2, 85 Thayer, R. E. Measurement of activation through self-report. Psychological Reports. 20 (1967): 663-678. Thayer, R. E., Takahashi, P. J., Pauli, J. A. (1988). Multidimensional arousal states, diurnal rhythm, cognitive and social processes, and extroversion. Personality and Individual Differences, 9, 15-24. Willis, J. (1990). Keeping time to circadian rhythms. FDA Consumer, 24(6), 18.