{"id":2100,"date":"2016-10-25T20:03:41","date_gmt":"2016-10-25T20:03:41","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/waymaker-psychology\/?post_type=chapter&#038;p=2100"},"modified":"2017-05-22T22:06:42","modified_gmt":"2017-05-22T22:06:42","slug":"outcome-consciousness","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-fmcc-intropsych\/chapter\/outcome-consciousness\/","title":{"raw":"Consciousness and Biological Rhythms","rendered":"Consciousness and Biological Rhythms"},"content":{"raw":"<h2>What you'll learn to do: describe consciousness and biological rhythms<\/h2>\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2016\/11\/16165526\/consciousnessimage.png\"><img class=\"aligncenter wp-image-2864\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2016\/11\/16165526\/consciousnessimage.png\" alt=\"consciousnessimage\" width=\"313\" height=\"454\" \/><\/a>\r\n\r\nAre you tired? Have you ever pulled an all-nighter? How did you feel the next day? Do you think your lack of sleep impacted your behavior? Chances are, you could answer that question with a resounding, \"yes!\". Because psychologists are interested in mental processes and behavior, it's essential\u00a0to study\u00a0consciousness, or our awareness, as humans. States of consciousness vary over the course of the day and throughout our lives, and sleep plays a major role in alertness levels. Important factors in daily changes in consciousness are biological rhythms, and, more specifically, the circadian rhythms generated by the suprachiasmatic nucleus. Typically, our biological clocks are aligned with our external environment, and light tends to be an important cue in setting this clock. When people travel across multiple time zones or work rotating shifts, they can experience disruptions of their circadian cycles that can lead to insomnia, sleepiness, and decreased alertness. If people go extended periods of time without sleep, they will accrue a sleep debt and potentially experience a number of adverse psychological and physiological consequences.\r\n<div class=\"textbox learning-objectives\">\r\n<h3>Learning Objectives<\/h3>\r\n<ul>\r\n \t<li>Describe consciousness and circadian rhythms<\/li>\r\n \t<li>Explain disruptions in biological rhythms, including sleep debt<\/li>\r\n<\/ul>\r\n<\/div>\r\n<div>\r\n<h2>Consciousness<\/h2>\r\n<strong>Consciousness<\/strong> describes our awareness of internal and external stimuli. Awareness of internal stimuli includes feeling pain, hunger, thirst, sleepiness, and being aware of our thoughts and emotions. Awareness of external stimuli includes seeing the light from the sun, feeling the warmth of a room, and hearing the voice of a friend.\r\n\r\n<\/div>\r\nWe experience different states of consciousness and different levels of awareness on a regular basis. We might even describe consciousness as a continuum that ranges from full awareness to a deep sleep. <strong>Sleep<\/strong> is a state marked by relatively low levels of physical activity and reduced sensory awareness that is distinct from periods of rest that occur during wakefulness. <strong>Wakefulness<\/strong> is characterized by high levels of sensory awareness, thought, and behavior. In between these extremes are states of consciousness related to daydreaming, intoxication as a result of alcohol or other drug use, meditative states, hypnotic states, and altered states of consciousness following sleep deprivation. We might also experience unconscious states of being via drug-induced anesthesia for medical purposes. Often, we are not completely aware of our surroundings, even when we are fully awake. For instance, have you ever daydreamed while driving home from work or school without really thinking about the drive itself? You were capable of engaging in the all of the complex tasks involved with operating a motor vehicle even though you were not aware of doing so. Many of these processes, like much of psychological behavior, are rooted in our biology.\r\n\r\n<section data-depth=\"1\">\r\n<h2>Biological Rhythms<\/h2>\r\n<strong>Biological rhythms<\/strong> are internal rhythms of biological activity. A woman\u2019s menstrual cycle is an example of a biological rhythm\u2014a recurring, cyclical pattern of bodily changes. One complete menstrual cycle takes about 28 days\u2014a lunar month\u2014but many biological cycles are much shorter. For example, body temperature fluctuates cyclically over a 24-hour period (Figure 1). Alertness is associated with higher body temperatures, and sleepiness with lower body temperatures.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"622\"]<img class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224622\/CNX_Psych_04_01_Rhythmsn.jpg\" alt=\"A line graph is titled \u201cCircadian Change in Body Temperature (Source: Waterhouse et al., 2012).\u201d The y-axis, is labeled \u201ctemperature (degrees Fahrenheit),\u201d ranges from 97.2 to 99.3. The x-axis, which is labeled \u201ctime,\u201d begins at 12:00 A.M. and ends at 4:00 A.M. the following day. The subjects slept from 12:00 A.M. until 8:00 A.M. during which time their average body temperatures dropped from around 98.8 degrees at midnight to 97.6 degrees at 4:00 A.M. and then gradually rose back to nearly the same starting temperature by 8:00 A.M. The average body temperature fluctuated slightly throughout the day with an upward tilt, until the next sleep cycle where the temperature again dropped. \" width=\"622\" height=\"447\" data-media-type=\"image\/jpg\" \/> Figure 1. This chart illustrates the circadian change in body temperature over 28 hours in a group of eight young men. Body temperature rises throughout the waking day, peaking in the afternoon, and falls during sleep with the lowest point occurring during the very early morning hours.[\/caption]\r\n\r\nThis pattern of temperature fluctuation, which repeats every day, is one example of a circadian rhythm. A <strong>circadian rhythm<\/strong> is a biological rhythm that takes place over a period of about 24 hours. Our sleep-wake cycle, which is linked to our environment\u2019s natural light-dark cycle, is perhaps the most obvious example of a circadian rhythm, but we also have daily fluctuations in heart rate, blood pressure, blood sugar, and body temperature. Some circadian rhythms play a role in changes in our state of consciousness.\r\n\r\nIf we have biological rhythms, then is there some sort of <strong>biological clock<\/strong>? In the brain, the hypothalamus, which lies above the pituitary gland, is a main center of homeostasis. <strong>Homeostasis<\/strong> is the tendency to maintain a balance, or optimal level, within a biological system.\r\n\r\nThe brain\u2019s clock mechanism is located in an area of the hypothalamus known as the <strong>suprachiasmatic nucleus (SCN)<\/strong>. The axons of light-sensitive neurons in the retina provide information to the SCN based on the amount of light present, allowing this internal clock to be synchronized with the outside world (Klein, Moore, &amp; Reppert, 1991; Welsh, Takahashi, &amp; Kay, 2010) (Figure 2).\r\n<figure>\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"366\"]<img class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224624\/CNX_Psych_04_01_SCN.jpg\" alt=\"In this graphic, the outline of a person\u2019s head facing left is situated to the right of a picture of the sun, which is labeled \u201dlight\u201d with an arrow pointing to a location in the brain where light input is processed. Inside the head is an illustration of a brain with the following parts\u2019 locations identified: Suprachiasmatic nucleus (SCN), Hypothalamus, Pituitary gland, Pineal gland, and Output rhythms: Physiology and Behavior. \" width=\"366\" height=\"241\" data-media-type=\"image\/jpg\" \/> Figure 2. The suprachiasmatic nucleus (SCN) serves as the brain\u2019s clock mechanism. The clock sets itself with light information received through projections from the retina.[\/caption]<\/figure>\r\n<\/section><section data-depth=\"1\">\r\n<h2>Problems with Circadian Rhythms<\/h2>\r\nGenerally, and for most people, our circadian cycles are aligned with the outside world. For example, most people sleep during the night and are awake during the day. One important regulator of sleep-wake cycles is the hormone <strong>melatonin<\/strong>. The <strong>pineal gland<\/strong>, an endocrine structure located inside the brain that releases melatonin, is thought to be involved in the regulation of various biological rhythms and of the immune system during sleep (Hardeland, Pandi-Perumal, &amp; Cardinali, 2006). Melatonin release is stimulated by darkness and inhibited by light.\r\n\r\nThere are individual differences with regards to our sleep-wake cycle. For instance, some people would say they are morning people, while others would consider themselves to be night owls. These individual differences in circadian patterns of activity are known as a person\u2019s chronotype, and research demonstrates that morning larks and night owls differ with regard to sleep regulation (Taillard, Philip, Coste, Sagaspe, &amp; Bioulac, 2003). <strong>Sleep regulation<\/strong> refers to the brain\u2019s control of switching between sleep and wakefulness as well as coordinating this cycle with the outside world.\r\n<div class=\"textbox examples\">\r\n<h3>Link to Learning<\/h3>\r\nWatch this brief video describing circadian rhythms and how they affect sleep.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=rtCQ9jzC-Ek\r\n\r\n<\/div>\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/2808\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/2809\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/4207\r\n\r\n<\/div>\r\n<section data-depth=\"2\">\r\n<div class=\"textbox learning-objectives\">\r\n<h3>Think It Over<\/h3>\r\n<section data-depth=\"1\">\r\n<div data-type=\"exercise\">\r\n<div data-type=\"problem\">We experience shifts in our circadian clocks in the fall and spring of each year with time changes associated with daylight saving time. Is springing ahead or falling back easier for you to adjust to, and why do you think that is?<\/div>\r\n<\/div>\r\n<\/section><\/div>\r\n<\/section><\/section>\r\n<h2 data-type=\"title\">Disruptions of Normal Sleep<\/h2>\r\nWhether lark, owl, or somewhere in between, there are situations in which a person\u2019s circadian clock gets out of synchrony with the external environment. One way that this happens involves traveling across multiple time zones. When we do this, we often experience jet lag. <strong>Jet lag<\/strong> is a collection of symptoms that results from the mismatch between our internal circadian cycles and our environment. These symptoms include fatigue, sluggishness, irritability, and <strong>insomnia<\/strong> (i.e., a consistent difficulty in falling or staying asleep for at least three nights a week over a month\u2019s time) (Roth, 2007).\r\n\r\nIndividuals who do rotating shift work are also likely to experience disruptions in circadian cycles. <strong>Rotating shift work<\/strong> refers to a work schedule that changes from early to late on a daily or weekly basis. For example, a person may work from 7:00 a.m. to 3:00 p.m. on Monday, 3:00 a.m. to 11:00 a.m. on Tuesday, and 11:00 a.m. to 7:00 p.m. on Wednesday. In such instances, the individual\u2019s schedule changes so frequently that it becomes difficult for a normal circadian rhythm to be maintained. This often results in sleeping problems, and it can lead to signs of depression and anxiety. These kinds of schedules are common for individuals working in health care professions and service industries, and they are associated with persistent feelings of exhaustion and agitation that can make someone more prone to making mistakes on the job (Gold et al., 1992; Presser, 1995).\r\n\r\nRotating shift work has pervasive effects on the lives and experiences of individuals engaged in that kind of work, which is clearly illustrated in stories reported in a qualitative study that researched the experiences of middle-aged nurses who worked rotating shifts (West, Boughton &amp; Byrnes, 2009). Several of the nurses interviewed commented that their work schedules affected their relationships with their family. One of the nurses said,\r\n<blockquote>If you\u2019ve had a partner who does work regular job 9 to 5 office hours . . . the ability to spend time, good time with them when you\u2019re not feeling absolutely exhausted . . . that would be one of the problems that I\u2019ve encountered. (West et al., 2009, p. 114)<\/blockquote>\r\nWhile disruptions in circadian rhythms can have negative consequences, there are things we can do to help us realign our biological clocks with the external environment. Some of these approaches, such as using a bright light as shown in Figure 1, have been shown to alleviate some of the problems experienced by individuals suffering from jet lag or from the consequences of rotating shift work. Because the biological clock is driven by light, exposure to bright light during working shifts and dark exposure when not working can help combat insomnia and symptoms of anxiety and depression (Huang, Tsai, Chen, &amp; Hsu, 2013).\r\n<figure>\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"325\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224626\/CNX_Psych_04_01_Brightlight.jpg\" alt=\"A photograph shows a bright lamp.\" width=\"325\" height=\"244\" data-media-type=\"image\/jpg\" \/> Figure 1. Devices like this are designed to provide exposure to bright light to help people maintain a regular circadian cycle. They can be helpful for people working night shifts or for people affected by seasonal variations in light.[\/caption]<\/figure>\r\n<section data-depth=\"2\">\r\n<h2 data-type=\"title\">Insufficient Sleep<\/h2>\r\nWhen people have difficulty getting sleep due to their work or the demands of day-to-day life, they accumulate a sleep debt. A person with a <strong>sleep debt<\/strong> does not get sufficient sleep on a chronic basis. The consequences of sleep debt include decreased levels of alertness and mental efficiency. Interestingly, since the advent of electric light, the amount of sleep that people get has declined. While we certainly welcome the convenience of having the darkness lit up, we also suffer the consequences of reduced amounts of sleep because we are more active during the nighttime hours than our ancestors were. As a result, many of us sleep less than 7\u20138 hours a night and accrue a sleep debt. While there is tremendous variation in any given individual\u2019s sleep needs, the National Sleep Foundation (n.d.) cites research to estimate that newborns require the most sleep (between 12 and 18 hours a night) and that this amount declines to just 7\u20139 hours by the time we are adults.\r\n\r\nIf you lie down to take a nap and fall asleep very easily, chances are you may have sleep debt. Given that college students are notorious for suffering from significant sleep debt (Hicks, Fernandez, &amp; Pelligrini, 2001; Hicks, Johnson, &amp; Pelligrini, 1992; Miller, Shattuck, &amp; Matsangas, 2010), chances are you and your classmates deal with sleep debt-related issues on a regular basis. The table below\u00a0shows recommended amounts of sleep at different ages.\r\n<table summary=\"This table has two columns and eight rows. The first row is a header row, and it labels the first column, \u201cage,\u201d and the second column \u201cnightly sleep needs.\u201d In the \u201cage\u201d column, the second row reads \u201c0\u20133 months.\u201d In the \u201cnightly sleep needs\u201d column, the second row reads \u201c12\u201318 hours.\u201d In the \u201cage\u201d column, the third row reads \u201c3 months\u20131 year.\u201d In the \u201cnightly sleep needs\u201d column, the third row reads \u201c14\u201315 hours.\u201d In the \u201cage\u201d column, the fourth row reads \u201c1\u20133 years.\u201d In the \u201cnightly sleep needs\u201d column, the fourth row reads \u201c12\u201314 hours.\u201d In the \u201cage\u201d column, the fifth row reads \u201c3\u20135 years.\u201d In the \u201cnightly sleep needs\u201d column, the fifth row reads \u201c11\u201313 hours.\u201d In the \u201cage\u201d column, the sixth row reads \u201c5\u201310 years.\u201d In the \u201cnightly sleep needs\u201d column, the sixth row reads \u201c10\u201311 hours.\u201d In the \u201cage\u201d column, the seventh row reads \u201c10\u201318 years.\u201d In the \u201cnightly sleep needs\u201d column, the seventh row reads \u201c8\u201310 hours.\u201d In the \u201cage\u201d column, the eighth row reads \u201c18 and older.\u201d In the \u201cnightly sleep needs\u201d column, the eighth row reads \u201c7\u20139 hours.\u201d\"><caption>Sleep Needs at Different Ages<\/caption>\r\n<thead>\r\n<tr>\r\n<th>Age<\/th>\r\n<th>Nightly Sleep Needs<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr>\r\n<td>0\u20133 months<\/td>\r\n<td>12\u201318 hours<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>3 months\u20131 year<\/td>\r\n<td>14\u201315 hours<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>1\u20133 years<\/td>\r\n<td>12\u201314 hours<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>3\u20135 years<\/td>\r\n<td>11\u201313 hours<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>5\u201310 years<\/td>\r\n<td>10\u201311 hours<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>10\u201318 years<\/td>\r\n<td>8\u201310 hours<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>18 and older<\/td>\r\n<td>7\u20139 hours<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nSleep debt and sleep deprivation have significant negative psychological and physiological consequences. As mentioned earlier, lack of sleep can result in decreased mental alertness and cognitive function. In addition, sleep deprivation often results in depression-like symptoms. These effects can occur as a function of accumulated sleep debt or in response to more acute periods of sleep deprivation. It may surprise you to know that sleep deprivation is associated with obesity, increased blood pressure, increased levels of stress hormones, and reduced immune functioning (Banks &amp; Dinges, 2007). Furthermore, individuals suffering from sleep deprivation can also put themselves and others at risk when they put themselves behind the wheel of a car or work with dangerous machinery. Some research suggests that sleep deprivation affects cognitive and motor function as much as, if not more than, alcohol intoxication (Williamson &amp; Feyer, 2000).\r\n<figure>\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"975\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224627\/CNX_Psych_04_01_Sleepless.jpg\" alt=\"An illustration of the top half of a human body identifies the locations in the body that correspond with various adverse affects of sleep deprivation. The brain is labeled with Irritability,\u201d \u201cCognitive impairment,\u201d \u201cMemory lapses or loss,\u201d \u201cImpaired moral judgement,\u201d \u201cSevere yawning,\u201d \u201cHallucinations,\u201d and \u201cSymptoms similar to ADHD.\u201d The heart is labeled with Increased heart rate variability and Risk of heart disease. The muscles are labeled with Increased reaction time, Decreased accuracy, Tremors, and Aches. There is an organ near the stomach labeled Risk of diabetes Type 2. Other risks include Growth suppression, Risk of obesity, Decreased temperature, and Impaired immune system.\" width=\"975\" height=\"522\" data-media-type=\"image\/jpg\" \/> Figure 2. This figure illustrates some of the negative consequences of sleep deprivation. While cognitive deficits may be the most obvious, many body systems are negatively impacted by lack of sleep. (credit: modification of work by Mikael H\u00e4ggstr\u00f6m)[\/caption]<\/figure>\r\n<div data-type=\"note\" data-label=\"Link to Learning\">\r\n<div class=\"textbox examples\">\r\n<h3>Link to Learning<\/h3>\r\nTo assess your own sleeping habits, read this <a href=\"https:\/\/sleepfoundation.org\/how-sleep-works\/how-much-sleep-do-we-really-need\" target=\"_blank\" rel=\"noopener noreferrer\">article<\/a> about sleep needs.\r\n\r\n<\/div>\r\n<\/div>\r\nThe amount of sleep we get varies across the lifespan. When we are very young, we spend up to 16 hours a day sleeping. As we grow older, we sleep less. In fact, a <strong>meta-analysis<\/strong>, which is a study that combines the results of many related studies, conducted within the last decade indicates that by the time we are 65 years old, we average fewer than 7 hours of sleep per day (Ohayon, Carskadon, Guilleminault, &amp; Vitiello, 2004). As the amount of time we sleep varies over our lifespan, presumably the sleep debt would adjust accordingly.\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/2812\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/2810\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/2811\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/4210\r\n\r\n<\/div>\r\n<div class=\"textbox learning-objectives\">\r\n<h3>Think It Over<\/h3>\r\n<section data-depth=\"1\">\r\n<div data-type=\"exercise\">\r\n<div data-type=\"problem\">\r\n\r\nWhat do you do to adjust to the differences in your daily schedule throughout the week? Are you running a sleep debt when daylight saving time begins or ends?\r\n\r\n<\/div>\r\n<\/div>\r\n<\/section><\/div>\r\n<\/section><section data-depth=\"1\">\r\n<div data-type=\"exercise\">\r\n<div data-type=\"problem\">\r\n<div data-type=\"exercise\">\r\n<div data-type=\"solution\">\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Glossary<\/h3>\r\n<section>\r\n<div data-type=\"note\">\r\n<div data-type=\"glossary\">\r\n<div data-type=\"definition\">\r\n<div data-type=\"definition\"><strong>biological rhythm:\u00a0<\/strong>internal cycle of biological activity<\/div>\r\n<div data-type=\"definition\"><strong>circadian rhythm:\u00a0<\/strong>biological rhythm that occurs over approximately 24 hours<\/div>\r\n<div data-type=\"definition\"><strong>consciousness:\u00a0<\/strong>awareness of internal and external stimuli<\/div>\r\n<div data-type=\"definition\"><strong>homeostasis:\u00a0<\/strong>tendency to maintain a balance, or optimal level, within a biological system<\/div>\r\n<div data-type=\"definition\"><strong>insomnia:\u00a0<\/strong>consistent difficulty in falling or staying asleep for at least three nights a week over a month\u2019s time<\/div>\r\n<div data-type=\"definition\"><strong>jet lag:\u00a0<\/strong>collection of symptoms brought on by travel from one time zone to another that results from the mismatch between our internal circadian cycles and our environment<\/div>\r\n<div data-type=\"definition\"><strong>melatonin:\u00a0<\/strong>hormone secreted by the endocrine gland that serves as an important regulator of the sleep-wake cycle<\/div>\r\n<div data-type=\"definition\"><strong>meta-analysis:\u00a0<\/strong>study that combines the results of several related studies<\/div>\r\n<div data-type=\"definition\"><strong>pineal gland:\u00a0<\/strong>endocrine structure located inside the brain that releases melatonin<\/div>\r\n<div data-type=\"definition\"><strong>rotating shift work:\u00a0<\/strong>work schedule that changes from early to late on a daily or weekly basis<\/div>\r\n<div data-type=\"definition\"><strong>sleep:\u00a0<\/strong>state marked by relatively low levels of physical activity and reduced sensory awareness that is distinct from periods of rest that occur during wakefulness<\/div>\r\n<div data-type=\"definition\"><strong>sleep debt:\u00a0<\/strong>result of insufficient sleep on a chronic basis<\/div>\r\n<div data-type=\"definition\"><strong>sleep regulation:\u00a0<\/strong>brain\u2019s control of switching between sleep and wakefulness as well as coordinating this cycle with the outside world\r\n<strong>suprachiasmatic nucleus (SCN):\u00a0<\/strong>area of the hypothalamus in which the body\u2019s biological clock is located<\/div>\r\n<div data-type=\"definition\"><strong>wakefulness:\u00a0<\/strong>characterized by high levels of sensory awareness, thought, and behavior<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n<\/section><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/section>\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/4818","rendered":"<h2>What you&#8217;ll learn to do: describe consciousness and biological rhythms<\/h2>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2016\/11\/16165526\/consciousnessimage.png\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-2864\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2016\/11\/16165526\/consciousnessimage.png\" alt=\"consciousnessimage\" width=\"313\" height=\"454\" \/><\/a><\/p>\n<p>Are you tired? Have you ever pulled an all-nighter? How did you feel the next day? Do you think your lack of sleep impacted your behavior? Chances are, you could answer that question with a resounding, &#8220;yes!&#8221;. Because psychologists are interested in mental processes and behavior, it&#8217;s essential\u00a0to study\u00a0consciousness, or our awareness, as humans. States of consciousness vary over the course of the day and throughout our lives, and sleep plays a major role in alertness levels. Important factors in daily changes in consciousness are biological rhythms, and, more specifically, the circadian rhythms generated by the suprachiasmatic nucleus. Typically, our biological clocks are aligned with our external environment, and light tends to be an important cue in setting this clock. When people travel across multiple time zones or work rotating shifts, they can experience disruptions of their circadian cycles that can lead to insomnia, sleepiness, and decreased alertness. If people go extended periods of time without sleep, they will accrue a sleep debt and potentially experience a number of adverse psychological and physiological consequences.<\/p>\n<div class=\"textbox learning-objectives\">\n<h3>Learning Objectives<\/h3>\n<ul>\n<li>Describe consciousness and circadian rhythms<\/li>\n<li>Explain disruptions in biological rhythms, including sleep debt<\/li>\n<\/ul>\n<\/div>\n<div>\n<h2>Consciousness<\/h2>\n<p><strong>Consciousness<\/strong> describes our awareness of internal and external stimuli. Awareness of internal stimuli includes feeling pain, hunger, thirst, sleepiness, and being aware of our thoughts and emotions. Awareness of external stimuli includes seeing the light from the sun, feeling the warmth of a room, and hearing the voice of a friend.<\/p>\n<\/div>\n<p>We experience different states of consciousness and different levels of awareness on a regular basis. We might even describe consciousness as a continuum that ranges from full awareness to a deep sleep. <strong>Sleep<\/strong> is a state marked by relatively low levels of physical activity and reduced sensory awareness that is distinct from periods of rest that occur during wakefulness. <strong>Wakefulness<\/strong> is characterized by high levels of sensory awareness, thought, and behavior. In between these extremes are states of consciousness related to daydreaming, intoxication as a result of alcohol or other drug use, meditative states, hypnotic states, and altered states of consciousness following sleep deprivation. We might also experience unconscious states of being via drug-induced anesthesia for medical purposes. Often, we are not completely aware of our surroundings, even when we are fully awake. For instance, have you ever daydreamed while driving home from work or school without really thinking about the drive itself? You were capable of engaging in the all of the complex tasks involved with operating a motor vehicle even though you were not aware of doing so. Many of these processes, like much of psychological behavior, are rooted in our biology.<\/p>\n<section data-depth=\"1\">\n<h2>Biological Rhythms<\/h2>\n<p><strong>Biological rhythms<\/strong> are internal rhythms of biological activity. A woman\u2019s menstrual cycle is an example of a biological rhythm\u2014a recurring, cyclical pattern of bodily changes. One complete menstrual cycle takes about 28 days\u2014a lunar month\u2014but many biological cycles are much shorter. For example, body temperature fluctuates cyclically over a 24-hour period (Figure 1). Alertness is associated with higher body temperatures, and sleepiness with lower body temperatures.<\/p>\n<div style=\"width: 632px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224622\/CNX_Psych_04_01_Rhythmsn.jpg\" alt=\"A line graph is titled \u201cCircadian Change in Body Temperature (Source: Waterhouse et al., 2012).\u201d The y-axis, is labeled \u201ctemperature (degrees Fahrenheit),\u201d ranges from 97.2 to 99.3. The x-axis, which is labeled \u201ctime,\u201d begins at 12:00 A.M. and ends at 4:00 A.M. the following day. The subjects slept from 12:00 A.M. until 8:00 A.M. during which time their average body temperatures dropped from around 98.8 degrees at midnight to 97.6 degrees at 4:00 A.M. and then gradually rose back to nearly the same starting temperature by 8:00 A.M. The average body temperature fluctuated slightly throughout the day with an upward tilt, until the next sleep cycle where the temperature again dropped.\" width=\"622\" height=\"447\" data-media-type=\"image\/jpg\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 1. This chart illustrates the circadian change in body temperature over 28 hours in a group of eight young men. Body temperature rises throughout the waking day, peaking in the afternoon, and falls during sleep with the lowest point occurring during the very early morning hours.<\/p>\n<\/div>\n<p>This pattern of temperature fluctuation, which repeats every day, is one example of a circadian rhythm. A <strong>circadian rhythm<\/strong> is a biological rhythm that takes place over a period of about 24 hours. Our sleep-wake cycle, which is linked to our environment\u2019s natural light-dark cycle, is perhaps the most obvious example of a circadian rhythm, but we also have daily fluctuations in heart rate, blood pressure, blood sugar, and body temperature. Some circadian rhythms play a role in changes in our state of consciousness.<\/p>\n<p>If we have biological rhythms, then is there some sort of <strong>biological clock<\/strong>? In the brain, the hypothalamus, which lies above the pituitary gland, is a main center of homeostasis. <strong>Homeostasis<\/strong> is the tendency to maintain a balance, or optimal level, within a biological system.<\/p>\n<p>The brain\u2019s clock mechanism is located in an area of the hypothalamus known as the <strong>suprachiasmatic nucleus (SCN)<\/strong>. The axons of light-sensitive neurons in the retina provide information to the SCN based on the amount of light present, allowing this internal clock to be synchronized with the outside world (Klein, Moore, &amp; Reppert, 1991; Welsh, Takahashi, &amp; Kay, 2010) (Figure 2).<\/p>\n<figure>\n<div style=\"width: 376px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224624\/CNX_Psych_04_01_SCN.jpg\" alt=\"In this graphic, the outline of a person\u2019s head facing left is situated to the right of a picture of the sun, which is labeled \u201dlight\u201d with an arrow pointing to a location in the brain where light input is processed. Inside the head is an illustration of a brain with the following parts\u2019 locations identified: Suprachiasmatic nucleus (SCN), Hypothalamus, Pituitary gland, Pineal gland, and Output rhythms: Physiology and Behavior.\" width=\"366\" height=\"241\" data-media-type=\"image\/jpg\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 2. The suprachiasmatic nucleus (SCN) serves as the brain\u2019s clock mechanism. The clock sets itself with light information received through projections from the retina.<\/p>\n<\/div>\n<\/figure>\n<\/section>\n<section data-depth=\"1\">\n<h2>Problems with Circadian Rhythms<\/h2>\n<p>Generally, and for most people, our circadian cycles are aligned with the outside world. For example, most people sleep during the night and are awake during the day. One important regulator of sleep-wake cycles is the hormone <strong>melatonin<\/strong>. The <strong>pineal gland<\/strong>, an endocrine structure located inside the brain that releases melatonin, is thought to be involved in the regulation of various biological rhythms and of the immune system during sleep (Hardeland, Pandi-Perumal, &amp; Cardinali, 2006). Melatonin release is stimulated by darkness and inhibited by light.<\/p>\n<p>There are individual differences with regards to our sleep-wake cycle. For instance, some people would say they are morning people, while others would consider themselves to be night owls. These individual differences in circadian patterns of activity are known as a person\u2019s chronotype, and research demonstrates that morning larks and night owls differ with regard to sleep regulation (Taillard, Philip, Coste, Sagaspe, &amp; Bioulac, 2003). <strong>Sleep regulation<\/strong> refers to the brain\u2019s control of switching between sleep and wakefulness as well as coordinating this cycle with the outside world.<\/p>\n<div class=\"textbox examples\">\n<h3>Link to Learning<\/h3>\n<p>Watch this brief video describing circadian rhythms and how they affect sleep.<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"Reprogramming Our Circadian Rhythms for the Modern World\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/rtCQ9jzC-Ek?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"lumen_assessment_2808\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=2808&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_2808\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<p>\t<iframe id=\"lumen_assessment_2809\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=2809&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_2809\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<p>\t<iframe id=\"lumen_assessment_4207\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=4207&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_4207\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<\/div>\n<section data-depth=\"2\">\n<div class=\"textbox learning-objectives\">\n<h3>Think It Over<\/h3>\n<section data-depth=\"1\">\n<div data-type=\"exercise\">\n<div data-type=\"problem\">We experience shifts in our circadian clocks in the fall and spring of each year with time changes associated with daylight saving time. Is springing ahead or falling back easier for you to adjust to, and why do you think that is?<\/div>\n<\/div>\n<\/section>\n<\/div>\n<\/section>\n<\/section>\n<h2 data-type=\"title\">Disruptions of Normal Sleep<\/h2>\n<p>Whether lark, owl, or somewhere in between, there are situations in which a person\u2019s circadian clock gets out of synchrony with the external environment. One way that this happens involves traveling across multiple time zones. When we do this, we often experience jet lag. <strong>Jet lag<\/strong> is a collection of symptoms that results from the mismatch between our internal circadian cycles and our environment. These symptoms include fatigue, sluggishness, irritability, and <strong>insomnia<\/strong> (i.e., a consistent difficulty in falling or staying asleep for at least three nights a week over a month\u2019s time) (Roth, 2007).<\/p>\n<p>Individuals who do rotating shift work are also likely to experience disruptions in circadian cycles. <strong>Rotating shift work<\/strong> refers to a work schedule that changes from early to late on a daily or weekly basis. For example, a person may work from 7:00 a.m. to 3:00 p.m. on Monday, 3:00 a.m. to 11:00 a.m. on Tuesday, and 11:00 a.m. to 7:00 p.m. on Wednesday. In such instances, the individual\u2019s schedule changes so frequently that it becomes difficult for a normal circadian rhythm to be maintained. This often results in sleeping problems, and it can lead to signs of depression and anxiety. These kinds of schedules are common for individuals working in health care professions and service industries, and they are associated with persistent feelings of exhaustion and agitation that can make someone more prone to making mistakes on the job (Gold et al., 1992; Presser, 1995).<\/p>\n<p>Rotating shift work has pervasive effects on the lives and experiences of individuals engaged in that kind of work, which is clearly illustrated in stories reported in a qualitative study that researched the experiences of middle-aged nurses who worked rotating shifts (West, Boughton &amp; Byrnes, 2009). Several of the nurses interviewed commented that their work schedules affected their relationships with their family. One of the nurses said,<\/p>\n<blockquote><p>If you\u2019ve had a partner who does work regular job 9 to 5 office hours . . . the ability to spend time, good time with them when you\u2019re not feeling absolutely exhausted . . . that would be one of the problems that I\u2019ve encountered. (West et al., 2009, p. 114)<\/p><\/blockquote>\n<p>While disruptions in circadian rhythms can have negative consequences, there are things we can do to help us realign our biological clocks with the external environment. Some of these approaches, such as using a bright light as shown in Figure 1, have been shown to alleviate some of the problems experienced by individuals suffering from jet lag or from the consequences of rotating shift work. Because the biological clock is driven by light, exposure to bright light during working shifts and dark exposure when not working can help combat insomnia and symptoms of anxiety and depression (Huang, Tsai, Chen, &amp; Hsu, 2013).<\/p>\n<figure>\n<div style=\"width: 335px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224626\/CNX_Psych_04_01_Brightlight.jpg\" alt=\"A photograph shows a bright lamp.\" width=\"325\" height=\"244\" data-media-type=\"image\/jpg\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 1. Devices like this are designed to provide exposure to bright light to help people maintain a regular circadian cycle. They can be helpful for people working night shifts or for people affected by seasonal variations in light.<\/p>\n<\/div>\n<\/figure>\n<section data-depth=\"2\">\n<h2 data-type=\"title\">Insufficient Sleep<\/h2>\n<p>When people have difficulty getting sleep due to their work or the demands of day-to-day life, they accumulate a sleep debt. A person with a <strong>sleep debt<\/strong> does not get sufficient sleep on a chronic basis. The consequences of sleep debt include decreased levels of alertness and mental efficiency. Interestingly, since the advent of electric light, the amount of sleep that people get has declined. While we certainly welcome the convenience of having the darkness lit up, we also suffer the consequences of reduced amounts of sleep because we are more active during the nighttime hours than our ancestors were. As a result, many of us sleep less than 7\u20138 hours a night and accrue a sleep debt. While there is tremendous variation in any given individual\u2019s sleep needs, the National Sleep Foundation (n.d.) cites research to estimate that newborns require the most sleep (between 12 and 18 hours a night) and that this amount declines to just 7\u20139 hours by the time we are adults.<\/p>\n<p>If you lie down to take a nap and fall asleep very easily, chances are you may have sleep debt. Given that college students are notorious for suffering from significant sleep debt (Hicks, Fernandez, &amp; Pelligrini, 2001; Hicks, Johnson, &amp; Pelligrini, 1992; Miller, Shattuck, &amp; Matsangas, 2010), chances are you and your classmates deal with sleep debt-related issues on a regular basis. The table below\u00a0shows recommended amounts of sleep at different ages.<\/p>\n<table summary=\"This table has two columns and eight rows. The first row is a header row, and it labels the first column, \u201cage,\u201d and the second column \u201cnightly sleep needs.\u201d In the \u201cage\u201d column, the second row reads \u201c0\u20133 months.\u201d In the \u201cnightly sleep needs\u201d column, the second row reads \u201c12\u201318 hours.\u201d In the \u201cage\u201d column, the third row reads \u201c3 months\u20131 year.\u201d In the \u201cnightly sleep needs\u201d column, the third row reads \u201c14\u201315 hours.\u201d In the \u201cage\u201d column, the fourth row reads \u201c1\u20133 years.\u201d In the \u201cnightly sleep needs\u201d column, the fourth row reads \u201c12\u201314 hours.\u201d In the \u201cage\u201d column, the fifth row reads \u201c3\u20135 years.\u201d In the \u201cnightly sleep needs\u201d column, the fifth row reads \u201c11\u201313 hours.\u201d In the \u201cage\u201d column, the sixth row reads \u201c5\u201310 years.\u201d In the \u201cnightly sleep needs\u201d column, the sixth row reads \u201c10\u201311 hours.\u201d In the \u201cage\u201d column, the seventh row reads \u201c10\u201318 years.\u201d In the \u201cnightly sleep needs\u201d column, the seventh row reads \u201c8\u201310 hours.\u201d In the \u201cage\u201d column, the eighth row reads \u201c18 and older.\u201d In the \u201cnightly sleep needs\u201d column, the eighth row reads \u201c7\u20139 hours.\u201d\">\n<caption>Sleep Needs at Different Ages<\/caption>\n<thead>\n<tr>\n<th>Age<\/th>\n<th>Nightly Sleep Needs<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>0\u20133 months<\/td>\n<td>12\u201318 hours<\/td>\n<\/tr>\n<tr>\n<td>3 months\u20131 year<\/td>\n<td>14\u201315 hours<\/td>\n<\/tr>\n<tr>\n<td>1\u20133 years<\/td>\n<td>12\u201314 hours<\/td>\n<\/tr>\n<tr>\n<td>3\u20135 years<\/td>\n<td>11\u201313 hours<\/td>\n<\/tr>\n<tr>\n<td>5\u201310 years<\/td>\n<td>10\u201311 hours<\/td>\n<\/tr>\n<tr>\n<td>10\u201318 years<\/td>\n<td>8\u201310 hours<\/td>\n<\/tr>\n<tr>\n<td>18 and older<\/td>\n<td>7\u20139 hours<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Sleep debt and sleep deprivation have significant negative psychological and physiological consequences. As mentioned earlier, lack of sleep can result in decreased mental alertness and cognitive function. In addition, sleep deprivation often results in depression-like symptoms. These effects can occur as a function of accumulated sleep debt or in response to more acute periods of sleep deprivation. It may surprise you to know that sleep deprivation is associated with obesity, increased blood pressure, increased levels of stress hormones, and reduced immune functioning (Banks &amp; Dinges, 2007). Furthermore, individuals suffering from sleep deprivation can also put themselves and others at risk when they put themselves behind the wheel of a car or work with dangerous machinery. Some research suggests that sleep deprivation affects cognitive and motor function as much as, if not more than, alcohol intoxication (Williamson &amp; Feyer, 2000).<\/p>\n<figure>\n<div style=\"width: 985px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/902\/2015\/02\/23224627\/CNX_Psych_04_01_Sleepless.jpg\" alt=\"An illustration of the top half of a human body identifies the locations in the body that correspond with various adverse affects of sleep deprivation. The brain is labeled with Irritability,\u201d \u201cCognitive impairment,\u201d \u201cMemory lapses or loss,\u201d \u201cImpaired moral judgement,\u201d \u201cSevere yawning,\u201d \u201cHallucinations,\u201d and \u201cSymptoms similar to ADHD.\u201d The heart is labeled with Increased heart rate variability and Risk of heart disease. The muscles are labeled with Increased reaction time, Decreased accuracy, Tremors, and Aches. There is an organ near the stomach labeled Risk of diabetes Type 2. Other risks include Growth suppression, Risk of obesity, Decreased temperature, and Impaired immune system.\" width=\"975\" height=\"522\" data-media-type=\"image\/jpg\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 2. This figure illustrates some of the negative consequences of sleep deprivation. While cognitive deficits may be the most obvious, many body systems are negatively impacted by lack of sleep. (credit: modification of work by Mikael H\u00e4ggstr\u00f6m)<\/p>\n<\/div>\n<\/figure>\n<div data-type=\"note\" data-label=\"Link to Learning\">\n<div class=\"textbox examples\">\n<h3>Link to Learning<\/h3>\n<p>To assess your own sleeping habits, read this <a href=\"https:\/\/sleepfoundation.org\/how-sleep-works\/how-much-sleep-do-we-really-need\" target=\"_blank\" rel=\"noopener noreferrer\">article<\/a> about sleep needs.<\/p>\n<\/div>\n<\/div>\n<p>The amount of sleep we get varies across the lifespan. When we are very young, we spend up to 16 hours a day sleeping. As we grow older, we sleep less. In fact, a <strong>meta-analysis<\/strong>, which is a study that combines the results of many related studies, conducted within the last decade indicates that by the time we are 65 years old, we average fewer than 7 hours of sleep per day (Ohayon, Carskadon, Guilleminault, &amp; Vitiello, 2004). As the amount of time we sleep varies over our lifespan, presumably the sleep debt would adjust accordingly.<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"lumen_assessment_2812\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=2812&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_2812\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<p>\t<iframe id=\"lumen_assessment_2810\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=2810&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_2810\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<p>\t<iframe id=\"lumen_assessment_2811\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=2811&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_2811\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<p>\t<iframe id=\"lumen_assessment_4210\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=4210&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_4210\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n<\/div>\n<div class=\"textbox learning-objectives\">\n<h3>Think It Over<\/h3>\n<section data-depth=\"1\">\n<div data-type=\"exercise\">\n<div data-type=\"problem\">\n<p>What do you do to adjust to the differences in your daily schedule throughout the week? Are you running a sleep debt when daylight saving time begins or ends?<\/p>\n<\/div>\n<\/div>\n<\/section>\n<\/div>\n<\/section>\n<section data-depth=\"1\">\n<div data-type=\"exercise\">\n<div data-type=\"problem\">\n<div data-type=\"exercise\">\n<div data-type=\"solution\">\n<div class=\"textbox key-takeaways\">\n<h3>Glossary<\/h3>\n<section>\n<div data-type=\"note\">\n<div data-type=\"glossary\">\n<div data-type=\"definition\">\n<div data-type=\"definition\"><strong>biological rhythm:\u00a0<\/strong>internal cycle of biological activity<\/div>\n<div data-type=\"definition\"><strong>circadian rhythm:\u00a0<\/strong>biological rhythm that occurs over approximately 24 hours<\/div>\n<div data-type=\"definition\"><strong>consciousness:\u00a0<\/strong>awareness of internal and external stimuli<\/div>\n<div data-type=\"definition\"><strong>homeostasis:\u00a0<\/strong>tendency to maintain a balance, or optimal level, within a biological system<\/div>\n<div data-type=\"definition\"><strong>insomnia:\u00a0<\/strong>consistent difficulty in falling or staying asleep for at least three nights a week over a month\u2019s time<\/div>\n<div data-type=\"definition\"><strong>jet lag:\u00a0<\/strong>collection of symptoms brought on by travel from one time zone to another that results from the mismatch between our internal circadian cycles and our environment<\/div>\n<div data-type=\"definition\"><strong>melatonin:\u00a0<\/strong>hormone secreted by the endocrine gland that serves as an important regulator of the sleep-wake cycle<\/div>\n<div data-type=\"definition\"><strong>meta-analysis:\u00a0<\/strong>study that combines the results of several related studies<\/div>\n<div data-type=\"definition\"><strong>pineal gland:\u00a0<\/strong>endocrine structure located inside the brain that releases melatonin<\/div>\n<div data-type=\"definition\"><strong>rotating shift work:\u00a0<\/strong>work schedule that changes from early to late on a daily or weekly basis<\/div>\n<div data-type=\"definition\"><strong>sleep:\u00a0<\/strong>state marked by relatively low levels of physical activity and reduced sensory awareness that is distinct from periods of rest that occur during wakefulness<\/div>\n<div data-type=\"definition\"><strong>sleep debt:\u00a0<\/strong>result of insufficient sleep on a chronic basis<\/div>\n<div data-type=\"definition\"><strong>sleep regulation:\u00a0<\/strong>brain\u2019s control of switching between sleep and wakefulness as well as coordinating this cycle with the outside world<br \/>\n<strong>suprachiasmatic nucleus (SCN):\u00a0<\/strong>area of the hypothalamus in which the body\u2019s biological clock is located<\/div>\n<div data-type=\"definition\"><strong>wakefulness:\u00a0<\/strong>characterized by high levels of sensory awareness, thought, and behavior<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n<p>\t<iframe id=\"lumen_assessment_4818\" class=\"resizable\" src=\"https:\/\/assessments.lumenlearning.com\/assessments\/load?assessment_id=4818&#38;embed=1&#38;external_user_id=&#38;external_context_id=&#38;iframe_resize_id=lumen_assessment_4818\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:400px;\"><br \/>\n\t<\/iframe><\/p>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-2100\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Original<\/div><ul class=\"citation-list\"><li>Modification, adaptation, and original content. <strong>Provided by<\/strong>: Lumen Learning. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>What is Consciousness?. <strong>Authored by<\/strong>: OpenStax College. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/Sr8Ev5Og@5.52:tefy7E6c@6\/What-Is-Consciousness\">http:\/\/cnx.org\/contents\/Sr8Ev5Og@5.52:tefy7E6c@6\/What-Is-Consciousness<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at http:\/\/cnx.org\/contents\/4abf04bf-93a0-45c3-9cbc-2cefd46e68cc@5.48<\/li><li><strong>Authored by<\/strong>: Robert Fludd. <strong>Provided by<\/strong>: Wikipedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/en.wikipedia.org\/wiki\/Consciousness#\/media\/File:RobertFuddBewusstsein17Jh.png\">https:\/\/en.wikipedia.org\/wiki\/Consciousness#\/media\/File:RobertFuddBewusstsein17Jh.png<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/pdm\">Public Domain: No Known Copyright<\/a><\/em><\/li><li>Reprogramming Our Circadian Rhythms for the Modern World. <strong>Authored by<\/strong>: Big Think. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/www.youtube.com\/watch?v=rtCQ9jzC-Ek\">https:\/\/www.youtube.com\/watch?v=rtCQ9jzC-Ek<\/a>. <strong>License<\/strong>: <em>Other<\/em>. <strong>License Terms<\/strong>: Standard YouTube License<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":29,"menu_order":2,"template":"","meta":{"_candela_citation":"[{\"type\":\"original\",\"description\":\"Modification, adaptation, and original content\",\"author\":\"\",\"organization\":\"Lumen Learning\",\"url\":\"\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"What is Consciousness?\",\"author\":\"OpenStax 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