{"id":373,"date":"2023-03-02T20:16:21","date_gmt":"2023-03-02T20:16:21","guid":{"rendered":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/chapter\/biological-rhythms\/"},"modified":"2023-09-05T17:59:10","modified_gmt":"2023-09-05T17:59:10","slug":"biological-rhythms","status":"publish","type":"chapter","link":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/chapter\/biological-rhythms\/","title":{"raw":"Sleep: Learn It 1\u2014Biological Rhythms","rendered":"Sleep: Learn It 1\u2014Biological Rhythms"},"content":{"raw":"<section class=\"textbox learningGoals\">\r\n<ul>\r\n \t<li>Explain circadian rhythms and how they can be disrupted<\/li>\r\n \t<li>Describe the brain structures and hormones involved in sleep<\/li>\r\n \t<li>Describe theories about the function of sleep<\/li>\r\n \t<li>Understand the difference between REM and non-REM sleep<\/li>\r\n \t<li>Describe the stages of sleep<\/li>\r\n \t<li>Compare and contrast theories about why we dream<\/li>\r\n<\/ul>\r\n<\/section><section data-depth=\"1\">\r\n<h2>Biological Rhythms<\/h2>\r\n<section class=\"textbox keyTakeaway\">\r\n<h3>Biological rhythms<\/h3>\r\n<strong>Biological rhythms<\/strong> are internal rhythms of biological activity. There are several types of biological rhythms, including:\r\n<ul>\r\n \t<li><strong>circadian rhythms<\/strong>: a biological rhythm that takes place over a period of about 24 hours. For example, changes in body temperature and alertness that fluctuate cyclically over a 24-hour period (Figure 1). Alertness is associated with higher body temperatures, and sleepiness with lower body temperatures.<\/li>\r\n \t<li><strong>infradian rhythms<\/strong>: a biological rhythm that lasts longer than 24 hours. A woman\u2019s menstrual cycle is an example of an infradian rhythm\u2014a recurring, cyclical pattern of bodily changes. One complete menstrual cycle takes about 28 days, or a lunar month.<\/li>\r\n \t<li><strong>ultradian rhythms<\/strong>: a biological rhythm that lasts less than 24 hours. For example, the rhythm of the body's appetite.<\/li>\r\n<\/ul>\r\n[caption id=\"attachment_6702\" align=\"aligncenter\" width=\"461\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28191941\/d2da772dbc0592c5fa2e39d56b50ba466a82bf60.jpeg\"><img class=\" wp-image-6702\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28191941\/d2da772dbc0592c5fa2e39d56b50ba466a82bf60.jpeg\" 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=\"461\" height=\"283\" \/><\/a> <strong>Figure 1<\/strong>. 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, and falls during sleep with the lowest point occurring during the very early morning hours.[\/caption]\r\n\r\n<\/section><span style=\"font-size: 1rem; text-align: initial;\">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\u00a0to our state of consciousness. Circadian and other rhythms are regulated by a variety of biological clocks within an organism. In humans, as with other vertebrate animals, these biological clocks are coordinated by a \"master clock\" known as the suprachiasmatic nucleus (SCN).<\/span>\r\n\r\n<section class=\"textbox keyTakeaway\">\r\n<h3>biological clock<\/h3>\r\nA <strong>biological clock<\/strong>, or an innate timing device,\u00a0is comprised of specific molecules (proteins) that interact in cells throughout the body. Research indicates that humans (as well as other animals, insects, fungi, and plants) have\u00a0biological clocks.\r\n\r\nSome form of a biological clock\u00a0is found in nearly every tissue and organ. In the brain, the hypothalamus, which lies above the pituitary gland, is a main center of homeostasis. <strong>Homeostasis<\/strong> is the self-regulating tendency of biological systems to maintain internal stability within a changing external environment.[footnote]Billman, G. E. (2020). Homeostasis: The Underappreciated and Far Too Often Ignored Central Organizing Principle of Physiology. <em>Frontiers in Physiology,<\/em> 11. https:\/\/doi.org\/10.3389\/fphys.2020.00200[\/footnote] In humans, the brain\u2019s main clock mechanism is located in an area of the hypothalamus known as the <strong>suprachiasmatic nucleus (SCN)<\/strong>. The SCN is comprised of about 20,000 nerve cells. 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).\r\n\r\n<\/section>\r\n<figure>\r\n\r\n[caption id=\"attachment_6707\" align=\"alignright\" width=\"402\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28192817\/a851b18bae062f1b52f4731e93a853e816aa45c5.jpeg\"><img class=\" wp-image-6707\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28192817\/a851b18bae062f1b52f4731e93a853e816aa45c5.jpeg\" 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=\"402\" height=\"264\" \/><\/a> <strong>Figure 2<\/strong>. The suprachiasmatic nucleus (SCN) serves as the brain\u2019s main clock mechanism. The SCN sets itself with light information received through\u00a0the retina of the eye.[\/caption]<\/figure>\r\n<\/section><section data-depth=\"1\">\r\n<h2>Problems with Circadian Rhythms<\/h2>\r\nGenerally, 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. People rely on external cues, such as light, atmospheric conditions, temperature, and social interactions, to set their\u00a0biological clocks.\r\n\r\n<section class=\"textbox connectIt\">\r\n<h3>Chronotypes<\/h3>\r\nThere\u00a0exist individual differences with\u00a0regard 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 <strong>chronotype.<\/strong>\r\n\r\nA person's individual chronotype may show that a person has a greater propensity to sleep earlier and wake up earlier (a morning lark), or to stay up late and sleep in (a night owl). 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\r\n<\/section><section><\/section><section class=\"textbox tryIt\">[ohm2_question height=\"650\"]3963[\/ohm2_question]<\/section><\/section>","rendered":"<section class=\"textbox learningGoals\">\n<ul>\n<li>Explain circadian rhythms and how they can be disrupted<\/li>\n<li>Describe the brain structures and hormones involved in sleep<\/li>\n<li>Describe theories about the function of sleep<\/li>\n<li>Understand the difference between REM and non-REM sleep<\/li>\n<li>Describe the stages of sleep<\/li>\n<li>Compare and contrast theories about why we dream<\/li>\n<\/ul>\n<\/section>\n<section data-depth=\"1\">\n<h2>Biological Rhythms<\/h2>\n<section class=\"textbox keyTakeaway\">\n<h3>Biological rhythms<\/h3>\n<p><strong>Biological rhythms<\/strong> are internal rhythms of biological activity. There are several types of biological rhythms, including:<\/p>\n<ul>\n<li><strong>circadian rhythms<\/strong>: a biological rhythm that takes place over a period of about 24 hours. For example, changes in body temperature and alertness that fluctuate cyclically over a 24-hour period (Figure 1). Alertness is associated with higher body temperatures, and sleepiness with lower body temperatures.<\/li>\n<li><strong>infradian rhythms<\/strong>: a biological rhythm that lasts longer than 24 hours. A woman\u2019s menstrual cycle is an example of an infradian rhythm\u2014a recurring, cyclical pattern of bodily changes. One complete menstrual cycle takes about 28 days, or a lunar month.<\/li>\n<li><strong>ultradian rhythms<\/strong>: a biological rhythm that lasts less than 24 hours. For example, the rhythm of the body&#8217;s appetite.<\/li>\n<\/ul>\n<figure id=\"attachment_6702\" aria-describedby=\"caption-attachment-6702\" style=\"width: 461px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28191941\/d2da772dbc0592c5fa2e39d56b50ba466a82bf60.jpeg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-6702\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28191941\/d2da772dbc0592c5fa2e39d56b50ba466a82bf60.jpeg\" 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=\"461\" height=\"283\" \/><\/a><figcaption id=\"caption-attachment-6702\" class=\"wp-caption-text\"><strong>Figure 1<\/strong>. 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, and falls during sleep with the lowest point occurring during the very early morning hours.<\/figcaption><\/figure>\n<\/section>\n<p><span style=\"font-size: 1rem; text-align: initial;\">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\u00a0to our state of consciousness. Circadian and other rhythms are regulated by a variety of biological clocks within an organism. In humans, as with other vertebrate animals, these biological clocks are coordinated by a &#8220;master clock&#8221; known as the suprachiasmatic nucleus (SCN).<\/span><\/p>\n<section class=\"textbox keyTakeaway\">\n<h3>biological clock<\/h3>\n<p>A <strong>biological clock<\/strong>, or an innate timing device,\u00a0is comprised of specific molecules (proteins) that interact in cells throughout the body. Research indicates that humans (as well as other animals, insects, fungi, and plants) have\u00a0biological clocks.<\/p>\n<p>Some form of a biological clock\u00a0is found in nearly every tissue and organ. In the brain, the hypothalamus, which lies above the pituitary gland, is a main center of homeostasis. <strong>Homeostasis<\/strong> is the self-regulating tendency of biological systems to maintain internal stability within a changing external environment.<a class=\"footnote\" title=\"Billman, G. E. (2020). Homeostasis: The Underappreciated and Far Too Often Ignored Central Organizing Principle of Physiology. Frontiers in Physiology, 11. https:\/\/doi.org\/10.3389\/fphys.2020.00200\" id=\"return-footnote-373-1\" href=\"#footnote-373-1\" aria-label=\"Footnote 1\"><sup class=\"footnote\">[1]<\/sup><\/a> In humans, the brain\u2019s main clock mechanism is located in an area of the hypothalamus known as the <strong>suprachiasmatic nucleus (SCN)<\/strong>. The SCN is comprised of about 20,000 nerve cells. 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).<\/p>\n<\/section>\n<figure>\n<figure id=\"attachment_6707\" aria-describedby=\"caption-attachment-6707\" style=\"width: 402px\" class=\"wp-caption alignright\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28192817\/a851b18bae062f1b52f4731e93a853e816aa45c5.jpeg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-6707\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/855\/2015\/02\/28192817\/a851b18bae062f1b52f4731e93a853e816aa45c5.jpeg\" 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=\"402\" height=\"264\" \/><\/a><figcaption id=\"caption-attachment-6707\" class=\"wp-caption-text\"><strong>Figure 2<\/strong>. The suprachiasmatic nucleus (SCN) serves as the brain\u2019s main clock mechanism. The SCN sets itself with light information received through\u00a0the retina of the eye.<\/figcaption><\/figure>\n<\/figure>\n<\/section>\n<section data-depth=\"1\">\n<h2>Problems with Circadian Rhythms<\/h2>\n<p>Generally, 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. People rely on external cues, such as light, atmospheric conditions, temperature, and social interactions, to set their\u00a0biological clocks.<\/p>\n<section class=\"textbox connectIt\">\n<h3>Chronotypes<\/h3>\n<p>There\u00a0exist individual differences with\u00a0regard 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 <strong>chronotype.<\/strong><\/p>\n<p>A person&#8217;s individual chronotype may show that a person has a greater propensity to sleep earlier and wake up earlier (a morning lark), or to stay up late and sleep in (a night owl). 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<\/section>\n<section><\/section>\n<section class=\"textbox tryIt\"><iframe loading=\"lazy\" id=\"ohm3963\" class=\"resizable\" src=\"https:\/\/ohm.one.lumenlearning.com\/multiembedq.php?id=3963&theme=lumen&iframe_resize_id=ohm3963&source=tnh&show_question_numbers\" width=\"100%\" height=\"650\"><\/iframe><\/section>\n<\/section>\n<hr class=\"before-footnotes clear\" \/><div class=\"footnotes\"><ol><li id=\"footnote-373-1\">Billman, G. E. (2020). Homeostasis: The Underappreciated and Far Too Often Ignored Central Organizing Principle of Physiology. <em>Frontiers in Physiology,<\/em> 11. https:\/\/doi.org\/10.3389\/fphys.2020.00200 <a href=\"#return-footnote-373-1\" class=\"return-footnote\" aria-label=\"Return to footnote 1\">&crarr;<\/a><\/li><\/ol><\/div>","protected":false},"author":20,"menu_order":9,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"What is Consciousness?\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-1-what-is-consciousness\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at https:\/\/openstax.org\/books\/psychology-2e\/pages\/1-introduction.\"},{\"type\":\"original\",\"description\":\"Reprogramming Our Circadian Rhythms for the Modern World\",\"author\":\"Big Think\",\"organization\":\"\",\"url\":\"https:\/\/www.youtube.com\/watch?v=rtCQ9jzC-Ek\",\"project\":\"\",\"license\":\"other\",\"license_terms\":\"Standard YouTube License\"},{\"type\":\"pd\",\"description\":\"Circadian rhythms\",\"author\":\"National Institute of General Medical Science\",\"organization\":\"\",\"url\":\"https:\/\/www.nigms.nih.gov\/education\/pages\/factsheet_circadianrhythms.aspx\",\"project\":\"\",\"license\":\"cc0\",\"license_terms\":\"\"},{\"type\":\"pd\",\"description\":\"Circadian Rhythms\",\"author\":\"\",\"organization\":\"National Institute of General Medical Sciences\",\"url\":\"https:\/\/nigms.nih.gov\/education\/fact-sheets\/Pages\/circadian-rhythms.aspx\",\"project\":\"\",\"license\":\"pd\",\"license_terms\":\"\"}]","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"part":364,"module-header":"learn_it","content_attributions":[{"type":"cc","description":"What is Consciousness?","author":"","organization":"OpenStax","url":"https:\/\/openstax.org\/books\/psychology-2e\/pages\/4-1-what-is-consciousness","project":"","license":"cc-by","license_terms":"Download for free at https:\/\/openstax.org\/books\/psychology-2e\/pages\/1-introduction."},{"type":"original","description":"Reprogramming Our Circadian Rhythms for the Modern World","author":"Big Think","organization":"","url":"https:\/\/www.youtube.com\/watch?v=rtCQ9jzC-Ek","project":"","license":"other","license_terms":"Standard YouTube License"},{"type":"pd","description":"Circadian rhythms","author":"National Institute of General Medical Science","organization":"","url":"https:\/\/www.nigms.nih.gov\/education\/pages\/factsheet_circadianrhythms.aspx","project":"","license":"cc0","license_terms":""},{"type":"pd","description":"Circadian Rhythms","author":"","organization":"National Institute of General Medical Sciences","url":"https:\/\/nigms.nih.gov\/education\/fact-sheets\/Pages\/circadian-rhythms.aspx","project":"","license":"pd","license_terms":""}],"internal_book_links":[],"video_content":null,"cc_video_embed_content":{"cc_scripts":"","media_targets":[]},"try_it_collection":null,"_links":{"self":[{"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/pressbooks\/v2\/chapters\/373"}],"collection":[{"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/wp\/v2\/users\/20"}],"version-history":[{"count":20,"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/pressbooks\/v2\/chapters\/373\/revisions"}],"predecessor-version":[{"id":6249,"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/pressbooks\/v2\/chapters\/373\/revisions\/6249"}],"part":[{"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/pressbooks\/v2\/parts\/364"}],"metadata":[{"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/pressbooks\/v2\/chapters\/373\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/wp\/v2\/media?parent=373"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/pressbooks\/v2\/chapter-type?post=373"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/wp\/v2\/contributor?post=373"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/wp-json\/wp\/v2\/license?post=373"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}