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PSYB64H3 (201)
Chapter 11

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Department
Psychology
Course
PSYB64H3
Professor
Janelle Leboutillier
Semester
Summer

Description
11 | SLEEP AND WAKING Circadian Rhythms - Sleep and waking cycles follow circadian rhythms: repeating cycle of about 24 hrs - In order to maintain rhythms, internal biological clocks interact w/ zeitgeber: external cue for setting biological rhythms light most important absence of light=free-running circadian rhythms: rhythm that isnt synchronized to environmental time cues (lasts approx. 24.2-24.9 hrs) - exposure to sunlight helps entrainentrainment: resetting of internal biological closk to 24hr cycle of earths rotation Variations in Sleep Patterns - individual sleep patterns = diffierent versions of genes responsible for internal clocks larks = most alert and productive in morning; night owls = night people; most lie between two extremes - nearly everyone acts like owls during adolescence melatonin (neurochemicals involved in regulation of sleep patterns) drops dramatically at onset of puberty = age related changes in sleep habits fllowing adolescence many temporary adults revert to previous state (probably due to maturation o neural systems that regulate sleep) Shift Work, Jet Lag, and Daylight Saving Time - (night shift workers) if work demands an circadian rhythms dont match = consequences are challenging and dangerous shift maladaptation syndrome frequent health, personality, mood, and interpersonal problems more accidents, more likely to develop breast cancer, more likely risk to others - jet lag: fatigue, irritability, and sleepiness resulting from travel across time zones - figure 11.3, p.315 easier to adjust to phase-delay of cycle, than to phase-advance daylight saving time phase advance in spring (equivalent to eastward travel=jet lag symptoms) & phase delay in fall Internal Clocks - bodys internal clock suprachiasmatic nucleus (SCN): area of hypothalamus located above optic chiasm; maintaining circadian rhythms figure 11.4, p.317 axons of special retinal ganglion cells non-image-forming (NIF) cells leave optic nerve, project to SCN = forms retinohypothalamic pathway: pathway leading from retina of eye to hypothalamus; provides light info necessary for maintenance of circadian rhythms NIF dont process info about visual images; contain melanopsin: photopigment used by NIF retinal cells - figure 11.5. p.318 SCN active only during day; regardless of whether diurnal (awake during day) or nocturnal (awake at night); helps distinguish between day and night - SCN not dependent on input from other structures to maintain rhythms acts as master clock = coordinates activities of other internal peripheral clocks existing in most body cells heavily influenced by presence of light; peripheral clocks easily influenced by daily feeding cycles The Cellular Basis of Circadian Rhythms - figure 11.6, p.317 three separate genes and their protein products involved w/ cellular circadian rhtyms 1) per (period) 2) tim (timeless) 3) clock (circadian locomotor output cycles kaput) - per & tim proteins inhibit clock proteins; clock protein promotes production of more per and tim proteins - neural activity reflects oscillation of lvls of these internal proteins = provide mechanism for communicating rhythms to other cells Biochemistry and Circadian Rhythm - SCN both regulates and responds to hormone melatonin: indoleamine secreted by pineal gland that participates in regulation of circadian rhythms lesions of SCN abolish circadian release of melatonin lvls very low during day, rise in hours before sleep, and usually peak at about 4am (time when mostly everybody finds it difficult to stay awake) blind individuals exp. melatonin peak at different time each day=sleep difficulties pineal gland tumors or other medical conditions affecting melatonin=report sleep problems release suppressed by light - melatonin supplements=improve cases of jet lag, shift maladaptation syndrome. and other sleep disorders helpful w/ visual impairments interfering w/ sleep patterns autism spectrum disorder use this to help regulate sleep patterns - figure 11.7, p.320 cortisol: hormone released by adrenal glands that promotes arousal fluctuate w/ patterns of waking and sleeping normally high early in morning and lower at night higher lvls=higher blood pressure, higher heart rate, and mobilization of bodys energy stores also released during times of stress; if during night=poor sleep quality might contribute to exp. of jet lagcould be stress of crossing time zones Seasonal Affective Disorder - (SAD): type of depression that results from insufficient amounts of daylight during the winter months - exact mechanisms not clear; serotonin lvls typically drop in fall & winter (ppl vulnerable to SAD=greater than normal decrease) - may also be caused by disruption in melatonin releasedcaused by uneven patterns of daily light - treated by exposure to bright lights (w/or w/out melatonin and antidepressants) light therapy- administered at dawn=for ppl who stay up too late; evening=helps ppl who are sleepy too early - not all populations that live at high latitudes exp. SAD frequently Stages of Wakefulness and Sleep - desynchronous: having different periods and phases; in EEG, represents high lvls of brain activity - synchronous: having identical periods and phases; EEG, represents relatively low lvls of brain activity Wakefulness - figure 11.8, p.321 EEG recordings alternate between beta & alpha wave patterns of brain activity beta wave: brain waveform having 15-20 cycles per second, associated w/ high lvls of alertness during wakefulness alpha wave: brain waveform having 9-12 cycles per second, associated w/ less alertness and more relaxation than beta activity during wakefulness - beta and alpha activity alternate throughout periods of wakefulness periods of high and low alertness follow ultradian cycles: cycle that occurs several times in a single day 90-120 min. in humansBrain Activity During Sleep - figure 11.9, p.321 recording activity of sleeping ppl isnt easy - consists of rapid-eye-movement (REM) and non-REM (NREM) sleep (REM): period of sleep characterized by desynchronous brain activity, muscle paralysis, eye movement, and storylike dream behaviour (NREM): period of sleep characterized by slow, synchronous brain activity, reductions in heart rate, and muscle relaxation - figure 11.10, p.322 sleep begins=enter stage 1 of NREM (difficult to distinguish from waking EEG of a drowsy person theta wave: brain waveform having 4-7 cycles per second found primarily in lighter stages of NREM sleep some occur @ stage 1; heart rate and muscle tension begin to decrease disturbed occasionally by myoclonia: muscle jerk occurring in early stages of sleep; often accompanied by brief visual image after 10-15 min, goes into stage 2 NREM (accounts for 50% of nights entire sleep; further reductions in heart rate and muscle tension) shows sleep spindles: short burst of 12-14 cps waves observed during NREM sleep; last about half a second; generated by interactions between thalamus and cortex; do occur in other stages of NREM) k-complex: brief burst of brain activity occurring during stage 2 slow-wave sleep (occur spontaneously; only seen in stage 2; also seen in response to unexpected stimuli) spindles and k-complexes might reflect brains effort to keep us asleep while monitoring external environment sleep through familiar stimuli, wake up at unfamiliar stimuli after 15min in stage 2 enter stage 3 & 4 NREM
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