sleep and circadian rhythms Flashcards
how can physiological activity be measured during sleep?
- electromyography measures muscle movements
- electro-oculography measures eye movements
- electroencephalography measures brain activity
how does an electroencephalogram work?
- electrodes placed on surface of scalp to detect electrical fields
- linked to an electrical amplifier and a monitor
what does an electroencephalogram measure?
electrical activity from large populations of neurons in the brain
caused by cellular, ionic movement, which creates an electric field
properties of electroencephalogram
- high temporal resolution - millisecond precision as electrodes in direct contact with scalp
- low spatial resolution - electrodes on scalp far away from neurons, signals decay and blur
five main stages of sleep
stage 1 - drowsiness (non-REM)
stage 2 - light sleep (non-REM)
stage 3 - deep sleep (non-REM)
stage 4 - very deep sleep (non-REM)
stage 4 - REM sleep
properties of non-REM sleep
- low neuronal activity
- low metabolic rate and brain temp
- heart rate and blood pressure decline (decreased sympathetic nervous system)
- increase in parasympathetic nervous system
- muscle tone and reflexes are intact
properties of stage 1 sleep
drowsiness
- awakened easily
- slow eye movement and muscle activity
properties of stage 2 sleep
light sleep
- eye movement stops
- brain waves slow with occasional burst of rapid brain
- body temp drops, heart rate slows
- begins to prepare for deep sleep
electrical characteristics of stage 1 sleep
EEG shows low-voltage activity of mixed frequencies (mostly theta waves)
electrical characteristics of stage 2 sleep
bursts of sinusoidal waves called ‘sleep spindles’ and biphasic waves called K complexes
properties of stage 3 sleep
deep sleep
- sleepwalking, night terrors, talking during sleep
electrical characteristics of stage 3 sleep
- slow delta waves interspersed with smaller, faster waves
properties of stage 4 sleep
very deep sleep
- disorientation for several minutes following arousal
electrical characteristics of stage 4 sleep
- delta waves almost exclusively
- slow wave activity dominates EEG
properties of stage 5 sleep
REM sleep
- eyes move rapidly from side-to-side
- EEG mimics wakefulness
why is REM sleep paradoxical?
REM-neuronal firing very like in wakefulness despite most muscles being relaxed
behavioural characteristics of REM sleep
- brain temp and metabolic rate rise
- skeletal muscles are atonic (paralysed)
- muscles controlling eye movement, middle ear ossicles and diaphragm remain active (to breathe and hear impending danger)
what regulates the circadian rhythm?
retinohypothalamic tract from eye to suprachiasmatic nucleus (internal clock) in anterior hypothalamus
what is the role of the visual system in circadian rhythm?
intrinsically photosensitive ganglion cells provide input to the suprachiasmatic nucleus
how is the brain stem associated with sleep?
brain stem regulates wakefulness
- lesion of brain stem can cause sleep and coma
- activation of neurons in brain stem precedes awakening
what are the roles of the raphe nuclei and locus coeruleus in sleep?
they are brain stem nuclei
- raphe nuclei source of 5-HT
- locus coeruleus source of norepinephrine
both important neurotransmitters in regulating sleep
