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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