4.2 Circadian Rhythms, Sleep, and Dreaming

circadian rhythm

animal’s daily rhythm of sleep, arousal, and metabolic functions

suprachiasmatic nucleus scn

structure in hypothalamus just superior to optic chiasm that plays an important role in establishing and maintaining circadian rhythms

pineal gland

structure just posterior to thalamus that secretes hormone melatonin

in conjunction with other structures, it plays an important role in circadian rhythms and sleep-wake cycles

melatonin 

hormone released from pineal gland and habenula that is in the highest concentrations at night and is lowest during the day 

chronotype 

an individual characteristic of preferences for sleep and wake times 

night owls prefer to stay up late and sleep in and morning larks go to bed and wake up early 

polysomnography psg 

instrument used in a sleep lab that measures several physiological responses during sleep, like eog, ecg, and eeg 

4 types of brainwaves associated with sleep and wakefulness

beta waves

alpha waves

theta waves

delta waves

beta waves

neurons are desynchronized

many waves at low amplitude

when awake and sleeping and dreaming

alpha waves 

more relaxed, resting 

higher amplitude than beta 

theta waves

sleep or deep meditation or daydreaming

large amplitudes

neurons synchronize

delta waves

highest amplitude

lowest frequency

deep sleep

sleep 2 categories 

REM 

NREM 

REM sleep

time during sleep when brain is very active and dreaming occurs

beta waves

NREM

three stages of sleep that are not REM sleep, which are most associated with deep sleep and low-frequency brainwaves such as theta and delta waves 

three stages of nonREM sleep

n1- alpha-theta waves, dream-like thoughts

n2- light sleep, sleep spindles or high-voltage activity

n3- deep slow-wave sleep of mostly delta brainwaves

activation-synthesis hypothesis

theory of dreaming in which cortex is trying to make sense of high activity in brainstem

dreams themselves have no underlying meaning

hobson and mccarley 1970s

insomnia 

common sleep disorder associated with inability to sleep 

associated with many health and psychological problems 

sleep apnea

common sleep disorder where someone wakes up constantly when trying to sleep because of breathing difficulties

sleep paralysis

inability to move or control muscles when awake

sleep paralysis typically happens just before falling asleep or while waking up

narcolepsy 

sleep disorder characterized by onset of feeling sleepy or loss of control of muscle movement during wakeful hours 

cataplexy

partial or total loss of muscle control

parasomnnia 

any of a number of sleep disorders that affect movement and behavior during sleep, such as night terrors, sleep paralysis, and REM sleep behavior disorder 

sleep hygiene

measures taken to improve sleep quality, such as a sleep routine, avoiding caffeine, and sleeping in a cool, dark, and quiet room

sleep hygiene list

keep a sleep routine

avoid caffeine esp later in the day

avoid alcohol

make room dark quiet and cool

avoid tv, phone, or computer screens

allow natural light to enter in morning

dont eat before sleeping

prioritize sleep

body and brain show patterns of activity and physiological changes that follow a 24-hr cycle, or circadian rhythm 

which is affected by the scn, pineal gland, behaviors, light, and hormones 

chronotype refers to a

person’s natural preferences for sleep and wake times

rem sleep is associated with

desynchronized brainwaves - beta

muscle relaxation - atonia

dreaming

rem occurs throughout night but mostly in 

early morning or end of a sleep cycle 

nrem/slow-wave sleep is associated with

synchronized brainwaves

occurs in 3 stages

-1 and 2 are light sleep- theta waves

-3 is deep sleep- delta waves

converting short-term to long-term memory (memory consolidation)

is facilitated by sleep, especially nrem sleep

poor sleep hinders emotional regulation and 

recognition of emotional states of others 

insomnia is inability to sleep and is caused or affected by several factors, including

sleep environment, stress, drugs and alcohol, and breathing problems such as sleep apnea

sleep paralysis can occur when a person is between stages of

sleep and wakefulness

narcolepsy is feeling the onset of

sleep or loss of muscle control/atonia when awake

parasomnia is a category of 

sleep disorder where people show odd behavior while sleeping, such as sleepwalking, talking, eating, and sexual behavior 

ways to improve sleep

sleep routine and avoid caffeine, psychostimulants, alcohol, screen time, and exercise before going to sleep, and make sleep environment quiet, dark, and cool

many recreational drugs like psychostimulants prevent

ability to fall asleep or impede stages of sleep