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

Where exactly is the biological clock?

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

Phase-Sequence Problems

• Fig. 9.5

• Fig. 9.6

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

• Relaxed wakefulness– Alpha waves

• Stage 1– Theta waves

Stages of Sleep

• Stage 2– Sleep spindles– K-complexes

Stages of Sleep

• Stage 3– Delta waves– Transition phase into Stage 4

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

Stages of Sleep

• Rapid Eye Movement (REM)

• EEG similar to Stages 1 and 2

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

Effects of REM Sleep Deprivation

• Irritability

• Concentration difficulty

• REM rebound

Things that affect REM Sleep

• Alcohol

• Sleeping pills

• REM rebound

Dreams

Table 9.2 Klein/Thorne: Biological Psychology© 2007 by Worth Publishers

Function of Sleep

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

Learning and Memory

• Memory consolidation

Sleep Disorders

Sleep Disorders

• Insomnia– Older adults, women– Noise, discomfort– Anxiety, depression– Caffeine, alcohol– Sleep apnea

Sleep Disorders

• Hypersomnia– Sleepwalking

• Non-REM– Night terror

• Non-REM• Different from nightmare

– Bedwetting• Non-REM• Treatment: conditioning

– Narcolepsy• REM• Cataplexy• Sleep paralysis