sleep and circadian rhythm Flashcards
whats does sleep control
-Change in behaviour
-Change in brain activity
-Structural changes- posture
-Gene expression
what does sleep consist of
-cycles of non-REM and REM sleep
what does REM stand for
-rapid eye movement
whats sleep defined behaviourally as
-Reduced motor activity
-Reduced response to stimulation- longer to respond to a stimuli, never completely stop responding to as timely because its dangerous
-Stereotypic postures (eye closed in humans)
-Relatively easy reversibility
how can Physiological activity can be conveniently measured using electrical recordings
-Muscle movements with electromyography- 2 electrodes which measure the difference in potential
-Eye movements with electro-oculography
-Brain activity with electroencephalography
what does a Electroencephalogram measure
-Measures the synchronous, electrical activity
from large populations of neurones in the brain
-Caused by cellular, ionic movement, which creates an electric field
-Many millions of neurones
-Electrodes placed on the surface of the scalp detect these electric fields
-Linked to an electrical amplifier (they are tiny electric fields) and to a monitor
what does low spatial resolution need
- a lot of neurones
-cm between electrode and brain
-further away from the source, smaller the signal
what are the main stages of non- REM sleep
1)Neuronal activity is low-not much action potential firing between neurones.
2)Metabolic rate and brain
temperature at their lowest.
3)Heart rate and blood pressure decline-
decreased sympathetic nervous system outflow
4)Increase in parasympathetic nervous system
5)Muscle tone and reflexes are intact
whats stage 1 of non REM sleep
-Drowsiness
-Awakened easily.
-Eyes move slowly and muscle activity slows.
-During this stage, many people experience sudden muscle contractions
preceded by a sensation of falling
-Transition from wakefulness to onset of sleep-lasts several minutes
-Eyes show slow, rolling movements
-During Stage 1 and all non-REM-
some muscular activity
-EEG characterised by low-voltage
activity if mixed frequencies (mostly theta waves)
whats stage 2 of non REM sleep
-Light Sleep
-Eye movement stops and brain waves become slower with only an occasional
-burst of rapid brain waves.
-The body begins to prepare for deep sleep
-Body temperature drops, heart rates slows
-Characterised by bursts of sinusoidal waves called
‘sleep spindles’ (12-14Hz) and biphasic waves called K complexes
-K complexes occur episodically against background
of continuing low-voltage EEG activity
whats stage 3 of non REM sleep
-Deep sleep.
-Extremely slow delta waves are interspersed with smaller, faster waves.
-sleepwalking, night terrors, talking during one’s sleep, and bedwetting ‘parasomnia’. Occur during the transitions between non-REM and REM sleep
whats stage 4 of non REM sleep
-Very deep sleep
-brain produces delta waves almost exclusively.
-Disorientation for several minutes following arousal from stage 4.
-Slow wave activity increases and dominates the EEG record
whats stage 5 of non REM sleep
-Rapid Eye Movement (REM) Sleep
EEG mimics wakefulness, REM found in birds
-Closed eyes move rapidly from side-to-side,
-Perhaps related to the intense dream and brain activity
-EEG during human REM is similar to Stage 1/A
what happens during REM sleep
-Brain temperature and metabolic rate rise-
=consistent with increased neural activity
=In some areas-greater than in waking
-All skeletal muscles are atonic- flaccid and paralysed
-Muscles controlling movements of the eye, middle ear ossicles,
and diaphragm remain active
whats the Normal Sleeping Pattern
-REM and non-REM sleep alternate cyclically
-Body movements/twitches during stages 1-2 and 2-3
-partial arousals in stages 1-2, 23, and 3-4
-After 70-80 minutes sleeper returns to stages 3 or even 2 before entering first
-REM phase of the night which lasts 8-10 minutes
-Time from first stage to end of REM = 90-110minutes
-Repeated four or five times per night-during each repetition, stages 3 & 4 decrease in duration and REM increases
sleep facts in young adults
-Only 5% of sleep time spent in Stage 1
-Largest amount of sleep time is spent in stage 2
-50-60% in stage 2
-Stages 3 and 4 only constitute 15-20%
-REM phases constitute only 20-25%
whats involved in the regulation of sleep
-Diffuse modulatory neurotransmission system
-NE and 5-HT neurons in the brain stem
-Diffuse modulatory system controls rhythmic behaviour in the Thalamus
-Inhibition of motor neurons
what does wakefulness consist of
-Lesion of the brain stem can cause sleep and coma
-Activation of neurons in brain stem precedes awakening.
-Stimulation of brain stem causes awakening
-Depolarising effect
facts about the none REM stage
-Decrease of firing in the brain stem
-Spindles – correlated activity in the thalamus
-Delta rhythms: activity in the thalamus
facts about the REM stage
-Fairly similar to firing in an awake state (but not early sensory systems)
-No activity in the frontal lobe
-No activity in raphe nuclei and locus coeruleus
-Inhibition of motor neurons
what are the theories of dreaming
-Strange imagery-brain not fully functioning
-Exercises synapses when no
external activity
-‘Memory consolidation’
-‘Circuit Testing’- brain test everything is working properly whilst asleep
what do sleep and wakefulness follow
-circadian rhythm with periodicity of about 24hrs
-Circadian rhythms are endogenous and persist without environmental cues- fall asleep and wake up independent from surroundings
-However they are modulated by external timing cues- ‘zeitgebers’
These adapt the rhythm to the environment
what do circadian clocks require
-sensory stimulation but works without them as well
-circadium rhythms can start shifting
-environmental queues are important for aligning circadian rhythms
what is the major internal clock
-suprachiasmatic nucleus of anterior hypothalamus
-Lesioning of the suprachiasmatic tract dampens down the circadian rhythm of sleep
-Suprachiasmatic nucleus regulates timing of sleep.
-Not responsible for sleep itself
