PSYCH 212 Chapter Notes - Chapter 10: Ultradian Rhythm, Melatonin, Melanopsin

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Chapter 10: Biological Rhythms and Sleep
Biological Rhythms
circadian rhythm - a pattern of behavioral, biochemical, or physiological fluctuation that
has a 24 hours period
ultradian - rhythmic biological period that is less than 24 hours
infraction - rhythmic biological period greater than 24 hours
-circadian rhythms are generated by an endogenous clock
free-running - referring to a rhythm of behavior shown by an animal deprived of external
cues about time of day
phase shift
entrainment - the process of synchronizing a biological rhythm to an environmental
zeitgeber - the stimulus that entrains circadian rhythm
-the hypothalamus houses a circadian clock
surachiasmatic nucleus (SCN) - a small region of the hypothalamus above the optic
chiasm that is the location of a circadian clock
-in mammals, light information for the eyes reaches the SCN directly
melatonin - an amine hormone that is secreted by the pineal gland at night, thereby
signaling day length to the brain
retinohypothalamic pathway - the route by which retinal ganglion cells send their axons
to the suprachiasmatic nuclei
melanopsin - a photopigment found in those retinal ganglion cells that project to the
suprachiasmatic nucleus
Sleep and Waking
-human sleep exhibits different stages
rapid eye movement (REM) sleep (paradoxical sleep) - a stage of sleep characterized
by small-amplitude, fast EEG waves, no postural tension and rapid eye movement
non-REM sleep - sleep, divided into stages 1-3, that is defined by the presence of
distinctive EEG activity that differs from that seen in REM sleep
desynchronized EEG (beta activity) - a pattern of EEG activity comprising a mix of many
different high frequencies with low amplitudes
alpha rhythm - a brain potential of 8-12 hertz that occurs during released wakefulness
vertex spike - a sharp-wave EEG pattern that is seen during stage 1 sleep
stage 1 sleep - the initial stage of non-REM sleep
-small amplitude EEG waves of irregular frequency, slow heart rate and reduced
muscle tension
stage 2 sleep - bursts of regular 14-18 hertz EEG waves called sleep spindles
sleep spindle - characteristic 14-18 hertz wave in the EEG of a person said to be in
stage 2 sleep
K complex - sharp, negative EEG potential that is seen in stage 2 sleep
stage 3 sleep (slow wave sleep) - a stage of non-REM sleep defined by the presence of
large-amplitude, slow delta waves
delta waves - the slowest type of EEG wave characteristic of stage 3 sleep
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