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Chapter 11

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Janelle Leboutillier

Chapter 11 PSYB64 Chapter 11 Sleep and Waking Circadian Rhythms  A repeating cycle of about 24 hours  Biological clocks interact with zeitgebers to maintain these rhythms  Zeitgebers: An external cue for setting biological rhythms (light is the most important) o Examples: Physical activity, feeding, body temperature, sleep-related hormones  Free-running circadian rhythms: A rhythm that is not synchronized to environmental time cues o Runs for about 24.2-24.9 hours in the absence of natural light  Entrainment: the resetting of internal biological clocks to the 24 hour cycle of the earth’s rotation which is usually done by the exposure to sunlight  Sailors and blind people have free running cycles longer than 24 hours leading to sleep disruption Variations in Sleep Patterns  Individual sleep patterns result from different versions of the genes responsible for internal clocks  Regardless of normal lifetime sleep patterns, adolescents are usually owls (stay awake at night)  Melatonin (neurochemical involved in sleep pattern regulation) levels drops at puberty onset o When neural systems mature, sleep patterns will go back to normal most of the time Shift Work, Jet Lag and Daylight Saving Time  When work demands and circadian rhythms do not match it can lead to shift maladaptation syndrome  Just 1.5 hours of less sleep can lead to frequent health, personality, mod and interpersonal problems  Night shift workers are more likely to develop breast cancer and the errors they make due to lack of sleep can harm the public  Jet lag: Fatigue, irritability, and sleepiness resulting from travel across time zones  It is easier to adjust to a phase delay of our cycle (setting the clock to a later point) than to phase- advance (setting the clock to an earlier point)  Fall shift of daylight saving time leads to less disruption  Spring shift produces similar symptoms to jet lag for 1-2 days Internal Clocks  Suprachiasmatic nucleus (SCN): an area of the hypothalamus located above the optic chiasm; responsible for maintaining circadian rhythms  The SCN is only active during the day even for nocturnal animals and helps distinguish whether it is day or night but other structures determine if they are nocturnal or diurnal o Diurnal means they are awake during the day  The SCN is not dependent on input from other structures to maintain rhythms  SCN is a master clock that coordinates activities of other internal peripheral clocks  Effects of phase shift on muscles and lungs and other tissue appear to last even after initial discomfort is gone  Rhythms of SCN is heavily influenced by light and the peripheral clocks are more easily influenced by daily feeding cycles  Axons of special retinal ganglion cells (aka non-imaging-forming (NIF) cells) leave optic nerve and project to the SCN producing retinohypothalamic pathway  Retinohypothalamic pathway: A pathway leading from the retina of the eye to the hypothalamus, provides light information necessary for the maintenance of circadian rhythms  NIF cells do not process info about visual images but contain melanopsin: a photopigment that is related to but different from other photopigments involved in vision Chapter 11 PSYB64 The Cellular Basis of Circadian Rhythms  The ebbing and flowing of special proteins require about 24 hours  Scientists found three genes (per, tim and Clock) and their protein products are involved with cellular circadian rhythms  Per and tim proteins inhibit the clock protein  Clock proteins promotes the production of more per and tim proteins  As per and tim protein levels drop over time, the reduced inhibition of the clock protein results in increased production of more per and tim proteins o DIAGRAM PAGE 318  This process helps us distinguish from one day to the next (internal clock) Biochemistry and Circadian Rhythms  SCN regulates and responds to melatonin  Melatonin: An indoleamine secreted by the pineal gland that participates in the regulation of circadian rhythms  Lesions of the SCN abolish the circadian release of melatonin  Melatonin levels are low during the day and are highest at around 4AM making it difficult to stay awake  Blind people have high levels of melatonin at different times each day making it hard to sleep o Melatonin release is suppressed by light  Pineal gland tumors or other melatonin affecting conditions can lead to sleep problems  Bright lights and indoor dim lights both have the ability to suppress production and release  People with autism spectrum disorder have low levels of melatonin  Melatonin treatment is used blind, autistic, jetlagged people as well as people with shift maladaptation syndrome  Cortisol: A hormone released by the adrenal glands that promotes arousal  Cortisol is normally high in the morning and lower at night  High levels of cortisol are associated with high BP, higher heart rate, mobilization of body’s energy stores and is released during times of stress  Stress and the high levels of cortisol can lead to poor sleep quality Seasonal affective Disorder  During winter months, the reduction in daylight hours can interfere with circadian rhythms  Seasonal affective disorder (SAD): A type of depression that results from insufficient amounts of daylight during the winter months  Serotonin levels typically drop in fall and winter so a greater than normal decrease may lead to SAD  May also be caused by disruption in melatonin release caused by uneven patterns of daily light  Treated by exposure to bright light and with or without melatonin and antidepressants  Light therapy is used at different times of day to help correct circadian rhythms  Usually seen in populations of areas of high altitudes Stages of Wakefulness and Seep  Desynchronous: Having different periods and phases; in EEG, represents high levels of brain activity o Correlated with alertness and independent action of individual neurons (more divers activities)  Synchronous: Having identical periods and phases; in EEG, represent relatively low levels of brain activity o Neurons fire in unison and characterizes deep stages of sleep Wakefulness  During this time, EEG recordings alternate between beta wave and alpha wave patterns of brain activity  Beta waves: A brain waveform having 15 to 20 cycles/second associated with high levels of alertness during wakefulness Chapter 11 PSYB64 o Highly desynchronized, rapid, irregular, low – amplitude waves o Person is actively thinking and very alert  Alpha waves: A brain waveform having 9 to 12 cycles/second, associated with less alertness and more relaxation than beta activity during wakefulness o Slower, larger and more regular than beta waves o Person is awake but quite relaxed  Ultradian cycles: A cycle that occurs several times in a single day o Made of alternating alpha and beta waves Brain Activity During Sleep  Rapid-eye-movement (REM) sleep: A period of sleep characterized by Desynchronous brain activity, muscle paralysis, eye movement and story-like dream behavior  Non-REM (NREM) sleep: A period of sleep characterized by slow, synchronous brain activity, reductions in heart rate, and muscle relaxation  Sleep begins at stage 1 of NREM  EEG is similar to waking EEG of drowsy person  Theta waves start to show  Theta waves: a brain waveform having 4 to 7 cycles per second found primarily in lighter stages of NREM sleep  Heart rate and muscle tension begin to decrease st  Myoclonia: A muscle jerk occurring in early stages of sleep that may disrupt the 1 stage of NREM sleep without harm to sleeper o Might be accompanied with a brief visual image of falling or tripping  After 10-15 min, stage 2 of NREM begins  Heart rate and muscle tensions further decrease  Sleep spindles: A short burst of 12 to 14 cycle-per-second waves that occur from thalamus and cortex interactions and is seen in other NREM stages of sleep  K-complex: A brief burst of brain activity that is only seen in stage 2; can also result from unexpected stimuli (loud noises)  Sleep spindles and K-complex reflect brain’s effort to keep us asleep while still monitoring external environment  Another 15 minutes is stage 3 and 4 of NREM sleep  Body temperature, breathing, blood pressure and heart rate are very low  Delta wave: A brain waveform having 1-4 cycles/second occurring in stages 3 and 4 of NREM sleep  Awakening from stage 4 is difficult and disorienting st  After 90 minutes of NREM, 1 period of REM sleep occurs (Paradoxical sleep)  Vivid dreaming occurs in REM  Transition from Stage 4 and REM is abrupt with brief passages between stage 3 and 2 of NREM  Ultradian cycles occur at this stage with 90min intervals (5 periods of REM in 8 hours of sleep)  Similar beta activity observed during wakefulness with occasional periods of theta activity  Eye make periodic back and forth movements  Sympathetic nervous system is very active  Heart rate, BP, breathing become rapid or irregular  Males  erection, females  blood flow in the vicinity of the vagina  Sleeper is paralyzed during major postural muscle inactivation  Fingers and other small muscles may twitch/jerk  PAGE 322 FOR SLEEP DIAGRAM Sleep Throughout the Life Span  Nightly sleep patterns change as a function of age  Newborns: 14 to 16 hours of sleep/day Chapter 11 PSYB64  Babies born prematurely show greater percentages of REM sleep than other infants  1 year old: 13 hours of sleep  Ages 1-5: 8.7 hours  Delta wave activity is highest between ages 3 and 6  At puberty there is a slight decrease in REM sleep and a great decrease in stage 3 and 4 sleep  NREM sleep declines as people approach midlife o PAGE 324 SLEEP OVER THE AGES GRAPH  Increased awakenings accompany a reduction in sleep spindles with age  Drops in sex hormones associated with aging might be responsible for changes in sleeping patterns with age  Menopausal women experience disruptions in sleep  Sex hormones have a direct role in regulation of biorhythms Dreaming During REM and NREM  Dreaming occurs during REM and NREM sleep  REM dreams are lengthy, complicated, vivid, story-like (feels like a firsthand experience)  NREM dreams are short episodes, logical single images and a relative lack of emotion  Studies showed that most dreams occur in familiar places and involve routine activities  Stranger are more likely to appear than familiar people  Sometimes dreams reflect ongoing neural activity (having water sprinkled on your face and then dreaming about rain)  Activation of vestibular system during REM sleep may lead to dreams of flying  Physical sexual arousal during REM sleep may lead to sexual content dreams  Two theories to advantages of dreaming o To process the day’s events o To practice escape methods during horrible situations  70% of our dreams have negative emotional content  Men report more aggression in their dreams than do women  Viewing upsetting entertainment/horrible news reports can increase likelihood of negative dreams  Nightmare: A REM dream with frightening content o First appear at around ages 3 and 6 and tend to decrease in frequency as puberty approaches  Recurrent, disturbing nightmares occur in many psychological disorder (PTSD)  Lucid dreaming: Thoughtful dreaming; the dreamer is aware that he or she is dreaming and can manipulate the experience  Night Terrors: An NREM episode occurring in the first three hours in which the individual is partially aroused, disoriented, frightened and inconsolable; different from nightmares  During night terrors, the person begins with an abrupt scream, followed by sweating and racing heartbeat o Sleeper sits upright and stares forward but not responsive o If awakened, the person will show disorientation and confusion o A feeling of pressure on the chest and is usually no memory of night terror the next day o Usually is a family history behind it and boys experience it more than girls o Most kids outgrow their night terror o Adults who still experience it my have anxiety or personality disorder The Function of Sleep  Fatal Familial Insomnia (FFI): middle-aged people who gradually lose the ability to sleep and eventually die Chapter 11 PSYB64 Sleep Keeps us Safe  Sleep prevents some animals from being active during parts of the day when they are leas safe from predation  Highly preyed upon animals sleep for a short period of time each day or they hi
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