Sleep, dreaming and circadian rhythms Flashcards
(30 cards)
how many hours do most people sleep in their lifetime
175000 hours
why do we sleep
sleep is due to an internal timing mechanism, it evolved to protect us from dangers of the night
do other animals sleep
animals have sleep
all mammals and birds sleep
what do sleep and wakefullness follow
circadian rythms with a periodicdity of about 24 hours
what are circadian rhythms
endogenous and persist without environmental cues
what are circadian rythms modulated by
external timing cues - zeotgebers
these adapt to the rythmn of the environment.
what does the hypothalamus control
body temperature, hunger, thirst and circadian cycles
what is the major internal clock called
suprachiasmatic nucleus
what does the SCN do
lesioning of the suprachiasmatic tract dampens down the circadian rhythm of sleep
regulates timing of sleep
not responsible for sleep itself
sleep deprivation studies with laboratory animals
experimental rats typically die after several days
postportem studies reveal the extreem stress experienced by experimental rats
what does sleep consist of
non REM and REM sleep
defined behaviourally as:
reduced motor activity
reduced response to stimulation
stereotypic postures
relatively easy reversibility
how can physiological activity be measures
using electrical recordings
-muslce movements with electromyography
-eye movemebnts with electro-oculography
brain activity with electroencephalography
stage one of sleep
transition between wakefulness and sleep; muscles are still active, the eyes who slow, gentle, rolling movements, some theta activity
stages 2 and 3
sleep gets deeper and deeper, the EEG gets progressively lower in frequency, and higher in amplitude
stage 4
the deepest stage of sleep; reached in less than an hour and contirnues for up to half an hour; characterised by relatively high amplitude EEG activity
REM sleep
the EEG looks like that of a person who is awake and active although EMG is generally quiet
what is the reticular formation
a set of interconnected nuclei that are located throughout the brainstem
-the reticular formation is not anotamically well defined because it includes neurons located in different parts of the brain
pontine reticular formation
part of the pontine reticular formation, a brain region without clearly defined borders in the centre of the pons
sleep deprivation in humans
logical deduction, critical thinking
physical stength and motor performance
executive function
innovative, lateral, insightful thinking
3-4 hours of deprivation in one night
increased sleepiness
disturbances displayed on written tests of mood
poor performance on tests of viligance
2-3 days of continuous deprivation
experience microsleeps, naps of 2-3 seconds
sleep deprivation increases sleep efficiency
after sleep deprivationb, most of last stage 4 is regained and slow wave sleep is increased
short sleepers get as much short wave sleep as long sleepers
naps without short wave sleep do not decrease the nights sleep
gradual reductions in sleep time lead to decreases in stages 1 and 2
little sleepiness produced with repeated REM awakenings, unlike short wave sleep
