Sleep. Internal Clock Circadian rhythm –Circum = about –Dies = day.
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Transcript of Sleep. Internal Clock Circadian rhythm –Circum = about –Dies = day.
Activities that are governed by an internal clock
• Waking and sleeping
• Eating and drinking
• Body temperature
• Secretion of hormonesFig. 9.1
Suprachiasmatic Nucleus (SCN)Figure 9.2 A sagittal view of the suprachiasmatic nucleus (SCN) and the pineal gland in the human brain Klein/Thorne: Biological Psychology© 2007 by Worth Publishers
SCN
• Controls the circadian rhythm
• Location– Hypothalamus– Just above the optic chiasm
• Damage to the SCN– Still sleep the same amount– But the daily rhythm is destroyed
• Affects sleep, release of hormones
Studying the human circadian rhythm
• Put healthy adults in a room with no indication of time of day– Body creates a rhythm that is about 25 hours
long– Indicates that if not reset, biological clock is
25 hours long– Free-running rhythm
Fig. 9.4
Studying the human circadian rhythm
• Zeitgebers– Reset the biological clock to 24 hours– Position of the sun, for example– Visual photoreceptor– Nonvisual photoreceptor (light-dark cycle)
• Retinohypothalamic tract – passes info from nonvisual photoreceptor to SCN
Wakefulness
• Reticular activating system (RAS)– Hindbrain through midbrain– Arousal of the brain, alertness
How to study sleep?• By using something called an
electroencephalograph (EEG)
• Electro: electric signals
• Encephalo: brain
• Graph: Measure
• Attach electrodes to the scalpFigure 9.13 EEG patterns during waking and sleeping, and a typical night’s sleepKlein/Thorne: Biological Psychology© 2007 by Worth Publishers
Stages of Sleep
• Caveat: there are now 3 NREM stages (Stages 3 and 4 have been combined), but textbook was published prior to this recent change
Stages of Sleep
• Stage 4– Delta waves
Stages 3 and 4: slow wave sleep
Controlled by the raphé nuclei, which contains serotonin decreased serotonin, decreased NREM sleep
REM Sleep
• Also called “paradoxical sleep”– EEG waves similar to waking state– Difficult to awaken person
• Loss of core muscle tone
REM Sleep
• Commonly associated with dreaming
• But, dreaming can occur during non-REM (NREM) sleep stages (1 through 4)
• REM sleep is produced by the caudal reticular formation
A restorative function• Growth• Development of nervous system• Replace neurotransmitters• More active during day need more sleep
Evolutionary Perspective• According to this theory, how much an
animal sleeps depends on – How much time it spends each day searching
for food– How safe it is from predators
Evolutionary Perspective• Cats and bats
– Eat nutritious food– Are relatively safe– Sleep for long periods of time
• Herbivores (plant eaters)– Graze much of the day– Need to look out for predators – Sleep in short spurts
Sleep Disorders
• Insomnia– Older adults, women– Noise, discomfort– Anxiety, depression– Caffeine, alcohol– Sleep apnea