4.1 biological rhythms & sleep

circadian rhythms

repeat every 24 hours

ultradian rhythms

repeat more than once a day

infradian rhythms

repeat less than once a day

zeitgeber

the external cue that animals use to figure out what time it is

suprachiasmatic nucleus (SCN)

biological clock responsible for rhythms; located in the hypothalamus above optic chiasm

what do lesions of the SCN do?

eliminate rhythms of drinking, hormone secretion, and movement

what did the transplant studies prove?

SCN produces the circadian rhythm

if the SCN is damaged…

subject becomes arrhythmic

free-running

not reliant on environmental cues

rapid-eye-movement sleep (REM)

small amplitude, fast EEG waves, rapid eye movements, atonia, dreams, secretion of GH

stage 1 sleep

decreased HR, muscle relaxation, less alpha rhythm, lower amp., irregular frequency, vertex spikes

stage 2 sleep

sleep spindles and k-complexes

nightmares

long scary dreams that wake you up from REM sleep

night terrors

the person seems awake but is asleep in stage 3 SWS, marked by fear, thrashing, and screaming

biological functions of sleep

energy conservation; muscular tension, heart rate, blood pressure, temperature, and respiration rate are reduced

four interacting neural systems

1. forebrain

2. brainstem

3. pontine

4. hypothalamic

forebrain system

promotes SWS

brainstem system

activates forebrain arousal between deep to light sleep or wakefulness

pontine system

triggers REM sleep

hypothalamic system

coordinates other three

narcolepsy

frequent sleep attacks, no SWS before REM sleep, cataplexy

sleep enuresis

bed wetting

somnambulism

sleep walking

insomnia

hard to fall asleep and get good sleep

sleep apnea

unable to breath when sleeping

REM behavior disorder

no paralysis leads to acting out dreams

sudden infant death syndrome (SIDS)

sudden death of a healthy infant who stops breathing during sleep

alert wakefulness

desynchronized EEG; low amp., high frequency, beta activity

slow-wave sleep (SWS)

large-amp., low freq. delta waves

how often does the sleep cycle repeat throughout the night

every 90-110 minutes

niche adaptation