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biological rhythms
a regular fluctuation in any living process
circadian rhythms
a pattern of behavioral, biochemical, or physiological fluctuation that has a 24-hour period
ultradian
referring to a rhythmic biological event with a period shorter than a day, usually from several minutes to several hours long
infradian
referring to a rhythmic biological event with a period longer than a day
free-running
referring to a rhythm of behavior shown by an animal deprived of external cues about time of day
period
the interval between two similar points of successive cycles (i.e. sunrise to sunset)
phase shift
a shift in the activity of a biological rhythm, typically provided by a synchronizing environmental stimulus, such as light
entrainment
the process of synchronizing a biological rhythm to an environmental stimulus
zeitgeber
“time giver” in German; the stimulus (usually the light-dark cycle) that entrains circadian rhythms
suprachiasmatic nucleus (SCN)
a small region of the hypothalamus above the optic chiasm that is the location of a circadian clock
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 specialized retical ganglion cells send their axins to the suprachiasmatic nuclei
melanopsin
a photopigment found in those retinal ganglion cells that project to the suprachiasmatic nucleus
electroencephalography (EEG)
a recording of gross electrical activity of the brain via large electrodes placed on the scalp
rapid-eye-movement (REM) sleep (aka paradoxical sleep)
a stage of sleep characterized by small-amplitude, fast EEG waves, no postural tension, and rapid eye movements
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 (aka beta activity)
a pattern of EEG activity comprising a mix of many different high frequencies with low amplitude
alpha rhythm
a brain potential of 8-12 Hz that occurs during relaxed wakefulness
vertex spikes
a sharp-wave EEG pattern that is seen during stage 1 sleep
stage 1 sleep
the initial stage of non-REM sleep, which is characterized by small-amplitude EEG waves of irregular frequency, slow heart rate, and reduced muscle tension
stage 2 sleep
a stage of sleep that is defined by bursts of EEG waves called sleep spindles
sleep spindles
a characteristic of 12-14 Hz wave in the EEG of a person said to be in stage 2 sleep
K complexes
a sharp, negative EEG potential that is seen in stage 2 sleep
stage 3 sleep (aka slow-wave sleep (SWS))
a stage of non-REM sleep that is defined by the presence of large-amplitude, slow delta waves
delta waves
the slowest type of EEG wave, about 1 per second, characteristic of stage 3 sleep
nightmare
a long, frightening dream that awakens the sleeper from REM sleep
night terror
a sudden arousal from stage 3 sleep that is marked by intense fear and autonomic activation
sleep deprivation
the partial or total prevention of sleep
sleep recovery
the process of sleeping more than normally after a period of sleep deprivation, as though in compensation
fatal familial insomnia
an inherited disease that causes people in middle age to stop sleeping, which after a few months results in death
ecological niche
the unique assortment of environmental opportunities and challenges to which each organism is adapted
isolated brain
an experimental preparation in which an animals brainstem has been separated from the spinal cord by a cut below the medulla
isolated forebrain
an experimental preparation in which an animal’s nervous system has been cut in the upper midbrain, dividing the forebrain from the brainstem
basal forebrain
a region in the forebrain, ventral to the basal ganglia, that is the major source of cholinergic projections in the brain; also implicated in sleep
tuberomammillary nucleus
a region of the basal hypothalamus, near the pituitary stalk, that plays a role in generating slow-wave sleep
general anesthetics
a drug that renders an individual unconscious
reticular formation (aka reticular activating system)
an extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal
locus coeruleus
a small nucleus in the brainstem whose neurons produce norepinephrine and modulate large areas of the forebrain
narcolepsy
a disorder that involves frequent, intense episodes of sleep, which last from 5 to 30 minutes and can occur anytime during the usual waking hours
cataplexy
sudden loss of muscle tone, leading to collapse of the body without loss of consciousness; sometimes a component of ncarcoleptic attacks
orexin (aka hypocretin)
a neuropeptide produced in the hypothalamus that is involved in switching between sleep states, in narcolepsy, and in the control of appetite
sleep paralysis
a state, during the transition to or from sleep, in which the ability to move or talk is temporarily lost
sleep enuresis
bed-wetting
somnambulism
sleepwalking
REM behavior disorder (RBD)
a sleep disorder in which a person physically acts out a dream
sleep-onset insomnia
difficulty in falling asleep
sleep-maintenance insomnia
difficulty in staying asleep
sleep state misperception
commonly, the perception of not having been asleep when in fact the person has been; typically occurs at the start of a sleep episode
sleep apnea
a sleep disorder in which respiration slows or stops periodically, waking the sleeper; excessive daytime sleepiness results from the frequent nocturnal awakening
sudden infant death syndrome (SIDS) (aka crib death)
the sudden, unexpected death of an apparently healthy human infant who simply stops breathing, usually during sleep
