Sleep and Biological Rhythms - Essay Example

 Sleep and Biological Rhythms Abstract This essay shed light on the basic principles of how the biological rhythms work, what are the different types of biological rhythms and how the cycle of rhythms repeat over a defined period of time. The other part of the essay explores the process of sleep and the stages of sleep in good detail. This highlights the brain state and activity during each process and how our body actions and thoughts are governed during each state. REM (i.e., Rapid Eye Movement Sleep) is the state of sleep during which dreaming occurs. The importance of sleep as a biological rhythm, and finally the essay discusses the three different disorders that may result due to disruption of circadian rhythms. Sleep and Biological Rhythms Most of the functions in animals are cyclic, recurring over a period of time one after another. Some of the obvious examples are the sleep-wake cycle, metabolism and urination. The sleep-wake cycle normally repeats every 24 hours in human beings, and in some animals it is in the form of hibernation patterns that allows them to rest during the times of winter and keep awake during spring. The major discussions regarding biological rhythms are the internal clocks or mechanisms through which they work. This essay attempts to analyze these biological rhythms, the types of rhythms and explores the nature, process and states of sleep in good detail. Biological Rhythms Biological Rhythms are any cyclic biological or physiological pattern of changes or activity in living beings that are often repeated daily, weekly, monthly, or through the annual cyclical changes in the living environment. These rhythms are determined by two factors: the internal clocks (also called the endogen factors) and the environmental factors (also called the zeitgebers). The nature and exact process of the biological clocks that control these cycles and rhythms are not known entirely. Diurnal animals (such as deer, goat, elephant and lions) are physically and mentally active during the daytime. In nocturnal animals (such as bat, cats, leopard, cockroaches and crickets) nighttime activity is dominant. Likewise many fishes and marine organisms’ activities are dependent on the tides. Examples of monthly rhythms include changes in weight of men and menstrual cycles in women. Annual cycles include those as bird migrations, reproductive activities etc. (Pearson Education). Daily cycles of changes are result of living being’s responses to daylight and dark, whereas the annual cycles are the result of the relative lengths of day and night over the year. The physiological changes and rhythms in fact follow the course of environmentally determined cyclical changes such as changes in weather, daylight, temperature and availability of food and resources. Hence internal rhythms stray away following the environmental cyclical changes. Activity of our individual organs also represent these physiological rhythms such as the contraction of muscles, heartbeat, blood pressure and the activity of electrical waves in the brain. Types of Biological Rhythms 1. Circadian Rhythms These are the biological process and cyclic variations occurring over an approximate period of 24-hours. These include some cycles that we are consciously aware of and observe in our daily lives, like sleep-wake routine; but we are not aware of most of these cycles that occur during the day, for instance the variation in our body temperature over a period of 24-hours. Our body temperature is highest at about 37.1 C at midafternoon and falls down to about 36.7 C at night hours. Other examples of circadian rhythms include heart rate, blood clotting, breathing and metabolism. Most of these follow the same cyclic pattern as body temperature since they match with the body activity. However, even people working on shifts (sleeping during day and working at night) demonstrate the same circadian rhythms as those working during the day. The authors Ruben et al. mentioned in their article that the intracellular molecular clocks that govern the circadian (24 hour) rhythms are understood to good extent. However it is not known how the clock information is converted into rhythmic neuronal activity as a result of which behavioral rhythms are formed. Although the intracellular molecular clocks that regulate circadian (~24 h) behavioral rhythms are well understood, it remains unclear how molecular clock information is transduced into rhythmic neuronal activity that in turn drives behavioral rhythms. 2. Ultradian Rhythms Ultradian Rhythms occur more than once in every 24-hour period. These may occur either during the day or night. An example of Ultradian Rhythm occurring during the night is the stages of sleep completing the sleep cycle. Stages of sleep are discussed in detail later in this essay. One sleep cycle lasts for about 90 minutes. These stages recur several times during the night depending on the duration of sleep. Those thythms occurring several times during the day include eating (like about every four or five hours), micturition, drinking and smoking for addicts [Bio12] . Infradian These rhythms repeat over the period of more than 24 hours. The best example of infradian rhythms in humans is the menstrual cycle in females. Some rhythms repeat even over a period of one year like birds migration. A typical human example could be Seasonal Affective Disorder (SAD). Sleep All animals need sleep. Mammals, birds and some other creatures sleep during the 24 hour period, whilst some animals also have hibernation periods. This indicates that sleep performs some essential and pivotal function for our body. Herbivores like Giraffe and Horses can sleep even while standing but they must lie down for the REM stage of sleep when muscle paralysis sets in, otherwise they would fall over. Compared to mammals, birds have relatively shorter sleep cycle. The duration of sleep highly varies in human beings. According to the 2010 American Time Use Survey, an average American sleeps 8.7 hours each day. Teenagers in America report to sleep 9.5 hours a day in average. Whereas adults of 65 and above report to sleep 9 hours a day. People in America sleep 9.5 hours on weekend, which is one hour greater than that on the weekdays. These are highly variable throughout the world and even within the same locations. 21% adults reported to sleep for only 6 hours, and another 8% reported that they sleep even less than 6 hours a day (Bureau of Labor Statistics, 2010). A good healthy sleep is necessary for human beings. Sleep deprivation studies tell us that sleep is extremely important to maintain psychological health and optimum levels of attentiveness, awareness and cognitive abilities. If a person goes three or four nights without sleep, it may result in hallucinations and paranoia but these are not long lasting. Stages of Sleep To understand both the process of sleep as well as the biological rhythms, it is very important to have a good understanding of the stages of sleep. Sleep is a perfect example of Ultradian biological rhythm. Until 1930s there were no scientific equipment or an objective way to measure the brain activity. However, after the invention of electroencephalogram (EEG), it was possible to record the electrical activity of the brain. This was a major breakthrough since the activity within our brain is mainly electrical in nature. Later it was found by various scientists that the brain doesn’t simply stops functioning or sending signals while we sleep, in fact, the electrical activity in the brain continues while we sleep and the waves generated become slower and larger. In 1953, Aserinsky & Kleitman coined the phrase Rapid Eye Movement (REM) which is a sleep state during which dreaming occurs. In 1968, Rechtschaffen & Kales recorded four other stages of sleep different from each other. The stages of sleep are discussed below. Stage 1 Sleep – 15 min Our sleep begins with this stage and all of us readily recognize this phase. It is when while watching TV or just laying on bed, or eyes begin to roll slowly, and we lose the will to stay awake. We may wake up from this stage without even realizing we were beginning to sleep, and sometimes we may wake up with a jerk. When we wake up from this stage we think we have been dreaming. In fact, these hallucinations are images lasting for a short time and these are also referred to as hypnogogic (i.e., sleep inducing) phenomenon. During this stage, brain waves are called “theta” and they are slower. Stage 2 Sleep – 20 min After about a minute we enter the stage 2 of sleep. In this stage we are aware of the surrounding activities and sounds around us and our brain does respond to them. Humans can still be easily awakened in this stage. Our brain emits high frequency waves called “sleep spindles”. Stage 3 Sleep – 15 min It is now more difficult to wake someone up from the third stage. The brain waves at this stage at called “delta” and they start becoming high in amplitude and wavelength. During the first sleep cycle at the night, this stage is very brief and lasts just a few minutes, but later at night during later sleep cycles, we spend more time in this stage. Stage 4 Sleep – 30 min The major brain activity is now comprised of the delta waves and we are now in the most relaxed state. Muscles are very relaxed and body temperature is the lowest at this point. Heart rate and blood pressure falls down. It is very difficult to wake people up from this stage and even forceful shaking might not be enough for someone to wake up, yet some meaningful and soft sound may be sufficient. This indicates that our brain is capable of responding to external stimuli even in this stage. Once we have been asleep for about an hour, we start to go back from stage 4 to stage 3 and then to stage 2.But instead to going to stage 1 we enter a very unusual state of consciousness called Rapid Eye Movement (REM). REM Sleep This is sometimes referred to as Stage 5 sleep or “paradoxical sleep”. After having passed through stage 4, 3 and then 2, our brain becomes very active almost as if it were awake. But despite the rapid eye movement, twitches and brain activity our body remains motionless. During this stage pons (A band of nerve fibers linking the medulla oblongata and the cerebellum with the midbrain) release a lot of electrical energy into the cerebral cortex. Our body temperature, blood pressure and heart rate rises. We dream during this stage of sleep, but our body is paralyzed which prevents us from acting out and responding to our dreams through our body and endanger our lives. Our very first journey in REM stage last not much long (for about 10 mins) and we go back to stage 2, moving on to third and then the fourth; but during the later sleep cycles at night we spend more time in REM. Therefore, as it is shown in the figure below, we spend most of our first half if a night’s sleep in deep (slow wave, NREM) sleep, and the most of our second half of a night’s sleep in REM sleep. The last sleep cycle during a night is called the “Emergent Cycle”. During this cycle we wake up and this cycle does not contain stage 3 or stage 4. So we may either be in REM or in Stage 2 Sleep while we wake up. While being awaken we may again experience the fleeting hypnogogic images. Remember that these are typical stages of an average person’s night sleep. The patterns may vary depending on different individuals, and the pattern also changes with age. People deprived of sleep will spend more time in stage 4 and REM sleep. The time duration of sleep in human beings differ with age. Due to this infants may sleep from 16 to 18 hours a day. Researches have been made about the sleeping and waking states in these infants. According to a research, polygraphic (A medical instrument that records several physiological processes simultaneously) recordings were obtained for about 12 hours in 20 healthy infants each of 1 week old. These recordings were taken at monthly intervals for four months. The recordings obtained were coded into various forms of quite sleep, active sleep, wakefulness and indeterminate. The percentages of active sleep and indeterminate proved to be a stable characteristic of each infants. However there was large variability noted which characterized immature sleep pattern among the infants. Due to this reason the polygraphic monitoring of sleep states is not useful for determining he early detection of abnormalities in infants (Hoppenbrouwers & et al., 1988) . According to Oswald (1966) both REM and NREM sleep is the time to restored our body’s depleted resources. Our body performs many restorative functions while we’re asleep such as aiding digestion, removal of waste from the muscles, and repairing of cells. During stages 3 and 4 our brain secretes growth hormone into the blood stream which stimulates proteins, amino acid uptakes and RNA synthesis (Lee Chiong, 2005); this in turn supports Oswald’s theory (Bentley, 1999). Sleep as a Biological Rhythm Earlier, during the 1960s, sleep was seen as a homeostatic system and it’s characteristics as a circadian rhythm were not explored. During late 1960s and early 1970s, the advancements in chronobiology greatly enhanced the research into the sleep process. As a result, by the 1980s sleep had been established as a major circadian rhythm. This was all possible because of rapid advancement and researches in the field of chronobiology (Webb, 1994). . Sleep Disorders Sleep being a circadian rhythm in human beings has the timing most important, so the cycle of sleep may be susceptible to disruption. It has also been known that problems in sleeping and some types of insomnia are the result of abnormalities in circadian rhythm. There are three main classes of sleep disorders that are the result of disruption of circadian rhythm: (1) Advanced sleep phase syndrome, which is common among the elder people and involves early onset and offset of sleep. Research shows that decreased Circadian cycle length and amplitude underlie this disorder; (2) Delayed sleep phase syndrome, also called insomnia, this is characterized by abnormally large delays of sleep onset and waking up. Teenagers and young adults are the most affected persons. It has been suggested that abnormally long circadian cycles and reduced responsiveness to the environment cold be the main cause of this problem. (3) Non-24-hour sleep wake disorder, this is also representative of disruption of the circadian cycle. Complaints of insomnia, difficulty in waking up, fatigue and tiredness are common in this type of disorder (Liskowsky & et al., 1991). Conclusion Biological Rhythms are a pivotal physiological and biological activity that is essential for our survival. Sleep is a basic type of circadian rhythm which comprises of several states as discussed above. Several studies and researches have been done from 1960s to 1980s in the field of neuroscience which has led to the complete understanding of the sleep. Furthermore, the disruption of biological rhythms may occur as a result of certain activities, that interact with other factors to degrade the sleep and create sleep disorders. The complete understanding of these processes has allowed us to deal with many sleep related problems. References Bentley, E. (1999). The resource library: Awareness: Biorhythms, Sleep and dreaming (Routledge Modular Psychology) (1st ed., p. 52). Routledge. Bureau of Labor Statistics. (2010). American time use survey. Retrieved from http://www.bls.gov/tus/charts/sleep.htm Lee Chiong, T. L. (2005). Sleep: A comprehensive handbook. (1st ed., p. 904). Wiley-Liss.Hoppenbrouwers, T., & et al., (1988). Journal sleep. Sleep And Waking States In Infancy: Normative Studies, 11(4), Retrieved from http://www.journalsleep.org/ViewAbstract.aspx?pid=25094 Liskowsky, D. R., & et al., (1991). Biological rhythms: Implications for the worker. new developments in neuroscience. (p. 51). DIANE Publishing Company. Pearson Education, publishing as Infoplease (n.d.). “rhythm, biological” Retrived November 7th, 2012 from http://www.infoplease.com/encyclopedia/science/rhythm-biological.html Psychology4a.com. Biological Rhythms. Retrieved from http://psychology4a.com/biological_rhythms.htm Ruben, M., & et al., (n.d.). Journal of biological rhythms. A Mechanism for Circadian Control of Pacemaker Neuron Excitability, Retrieved from http://jbr.sagepub.com/content/27/5/353.abstract Webb, W. B. (1994). Journal sleep. Sleep As A Biological Rhythm: A Historical Review, 17(2), Retrieved from http://www.journalsleep.org/ViewAbstract.aspx?pid=24677 Read More