Chapter 10: Biological Rhythms & Sleep

Made by @agreyr

How the brain controls sleep

1. Forebrain system that generates SWS

2. Brainstem system that activates the sleeping forebrain to wakefulness (reticular activating system of the brainstem)

3. Pontine system that triggers REM sleep (REM sleep nuclei in the pons)

4. Hypothalamic system that coordinates the others

Sleep disorders

Insomnia, hypersomnia, sleep apnea, unreliable respiration, nocturnal myoclonus, narcolepsy, nightmares, night terror, REM behavior disorder, sleep paralysis

Sleep apnea

Unreliable respiration

Nocturnal myoclonus

Restless leg syndrome

Nightmares vs night terror

Nightmares are frightening dreams; night terror is arousal from SWS, intense fear

Narcolepsy

Daytime sleep attacks, cataplexy, sleep hallucinations

REM behavior disorder

Act out a dream while sleeping

Sleep paralysis

Inability to talk/move upon waking or falling asleep

Drugs that affect sleep

Hypnotic drugs and anti-hypnotic drugs

Hypnotic drugs

Benzodiazepines, Ambien, Melatonin

Anti-hypnotic drugs

Stimulants and tricyclic antidepressants

Benzodiazepines

Hypnotic drug

Short-term effects: increase drowsiness, decrease time it takes to fall asleep, reduce number of awakenings, increase total sleep time

Chronic use not recommended; tolerance develops, cessation of use causes insomnia, chronic use causes addiction, they distort the normal pattern of sleep

Ambien

Hypnotic drug

FDA approved for short-term treatment of insomnia; non-benzodiazepine hypnotic but binds to the benzodiazepine site of GABA

Side effects: drowsiness, sleepiness, headache, dizziness, memory impairment, muscle and joint pain

Tolerance, dependance, and withdrawal are possible

Melatonin

Hypnotic drug; a hormone synthesized from serotonin in the pineal gland

Circulating levels of melatonin display circadian rhythms (SCN of the hypothalamus; highest levels associated with darkness and sleep, usefulness is disputable

Stimulants and tricyclic antidepressants

Increase activity of catecholamines by increasing release, blocking reuptake, or both

They act preferentially on REM sleep; can totally suppress REM sleep

Chronic use not recommended; highly addictive, adverse side effects, can interfere with normal sleep

Standard sleep measures

Electroencephalogram (EEG), Electrooculogram (EOG), Electromyogram (EMG)

Electroencephalogram (EEG)

Allows us to look at brain activity through wave patterns

Electrooculogram (EOG)

Analyzing specific muscle movements around the eye (REM vs NREM)

Electromyogram (EMG)

Identifying muscle activity (or lack thereof) in the neck

EEG patterns

Wakefulness, stage 1 sleep EEG, stage 2 sleep EEG, stage 3 sleep EEG

Wakefulness (EEG)

Desynchronized EEG (beta activity)

Stage 1 sleep EEG

Alpha waves and vertex spikes; slowing of the heart rate and relaxation of the muscles

Stage 2 sleep EEG

K complexes and sleep Spindles

Stage 3 sleep EEG

Slow wave sleep; delta waves

REM sleep

Rapid eye movements; loss of core muscle tone (atonia), brainstem regions inhibit motor neurons; low amplitude, high frequency EEG; cerebral activity increases to waking levels; general increase in ANS activity; occasional muscle twitching in extremities; more prominent in later half of sleep cycle

REM and dreaming/dream recall

If you wake people up during REM or NREM sleep, 80% of awakenings from REM sleep but only 7% of awakenings from NREM sleep led to dream recall

Dream interpretation theories

Freudian theory and Hobson’s activation-synthesis theory

Freudian theory of dream interpretation

Dreams represent unacceptable wishes; can determine real desires by understanding the meaning of the dreams we experience

Hobson’s activation-synthesis theory

Information supplied to the cortex during dreaming is largely random and the dream is the cortex attempting to make sense of it; meaning comes from what the people add to the random jumble

Theories on the purpose of sleep

Recuperation theories and adaptation theories

Recuperation theories of sleep

Being awake disrupts homeostasis and sleep is required to restore it
Sleepiness triggered by deviation from homeostasis caused by wakefulness; sleep is terminated by the return to homeostasis

Adaptation theories of sleep

Sleep is the result of an internal timing mechanism

Humans programmed to sleep at night to avoid accidents and predation and to save energy

Purpose of sleep

It fulfills some necessary physiological function; probably not some complex higher order one, as most mammals and birds sleep

Sleep is essential for survival but not necessarily needed in massive quantities

Sleep patterns across the lifespan

Infants sleep a lot, with decreases throughout childhood

• REM sleep likely important for nervous system and brain development in infants; high proportions of REM sleep in infants

Increased need for sleep in adolescence

• Shift in circadian rhythms for sleep/wake cycles; research shows benefits when these shifts are built into society with later school start times (increased academic performance, fewer driving accidents, and reduced depression rates)

Effects of sleep deprivation in humans

Increase in sleepiness, irritability, difficulty concentrating

Severe sleep deprivation can result in occasional hallucinations

REM rebound (sleep recovery)

You won’t make up for the sleep you lost but you may have more intense sleep for a few days

Sleep functions

Energy conservation, niche adaptation, body & brain restoration, memory consolidation

Energy conservation

Reduced metabolic activity when we sleep

Niche adaptation

Sleep is part of an organism’s ecological niche; emphasizes the role of natural selection

Body & brain restoration

Prolonged deprivation leads to lower immune function; people more susceptible to pain after sleep deprivation

Memory consolidation

Slow wave sleep and REM may plan an important role; synaptic rearrangement occurs during REM

Biological rhythms

Repeating, predictable fluctuations over time; almost all biological functions have a rhythm

Ultradian rhythm

Any biological process that repeats more than once in a day (activity, feeding, some hormone release)

Infradian rhythm

Any biological process that repeats less than once in a day (menstrual cycle, breeding cycle in some animals, seasonal patterns of depression, hibernation)

Circadian (daily) rhythm

Any biological process that cycles through changes in approximately 24 hours (hormone levels, body temp, etc.)

Generated by an endogenous (internal) clock

Adapt to the light-to-dark cycles of the day based on Zeitgebers

Diurnal

Awake during the day, sleep at night (humans & primates)

Nocturnal

Active during dark periods (most other mammals)

Zeitgebers

Environmental cues that control the timing of circadian rhythms

Can be manipulated in laboratory settings; presumed to work via mechanisms in the suprachiasmatic nucleus of the hypothalamus (SCN)

Most obvious one is the circadian sleep-wake cycle

Free-running circadian cycle

In an environment devoid of Zeitgebers, humans and animals still maintain the circadian rhythms, approximately 25 hours in humans; they do not have to be learned

Phase shift

Shift in activity caused by a stimulus (night shift workers)

Entertainment

The process of shifting (jet lag)