Biological - NIH Office of Science Education - National Institutes of ...

Sleep, Sleep Disorders, and Biological Rhythms
homeostatic regulation of sleep: Refers to the
neurobiological signals mediating the pressure or
urge to sleep.
hypnagogic hallucination: A “greater-than-lifelike”
dream experience that occurs during sleep.
Hypnagogic hallucinations are sometimes associated
with narcolepsy.
hypnogram: A graphical summary of the electrical
activities occurring during a night’s sleep.
hypothalamus: The part of the brain that lies
below the thalamus and regulates body temperature
and metabolic processes.
insomnia: Sleeplessness; chronic difficulty with
sleep onset or maintenance of sleep, or a perception
of nonrefreshing sleep.
luteinizing hormone: A glycoprotein secreted by
the pituitary gland. It stimulates the gonads to
secrete sex steroids.
melatonin: A hormone secreted by the pineal
gland that is derived from the amino acid tryptophan,
which helps synchronize biological clock
neurons in the suprachiasmatic nucleus.
narcolepsy: A chronic sleep disorder characterized
by excessive and overwhelming daytime
sleepiness (even after adequate nighttime sleep).
neurotransmitter: A chemical produced by neurons
that carries messages to other neurons.
nocturnal: Relating to or taking place at night.
non–rapid eye movement (NREM) sleep: The
early phase of sleep with no rapid eye movement.
obstructive sleep apnea (OSA) (sleep apnea syndrome,
sleep-disordered breathing): A disorder
in which breathing is frequently interrupted for
brief intervals during sleep, resulting in intermittent
decreases in blood oxygen levels and transient
arousals from sleep, leading to poor sleep
quality and excessive daytime sleepiness.
oscillation: The state or act of swinging back and
forth with a regular, uninterrupted pattern.
parasomnias: Sleep disorders that include sleepwalking,
sleep talking, and sleep terrors.
photoperiod: The light/dark or day/night cycle.
photoreceptor: A molecule or structure that can
detect light.
pons: The brainstem region critical for initiating
REM sleep.
rapid eye movement (REM) sleep: Deep sleep
with rapid eye movements in which dreaming
takes place.
restless legs syndrome: A neurologic movement
disorder that is often associated with a sleep complaint.
seasonal affective disorder (SAD): A form of
depression caused by inadequate bright light
reaching the biological clock in the suprachiasmatic
nucleus. Consequently, treatment often
involves the use of light therapy.
sleep hygiene: The collection of behaviors and
environmental conditions that influence the
length and quality of sleep.
sleep paralysis: The temporary inability to talk or
move when falling asleep or waking up. It occurs
normally during REM sleep.
suprachiasmatic nucleus (SCN): The part of the
brain (in the hypothalamus) that contains the biological
clock.
thalamus: The area of the brain that relays sensory
information to the cerebral cortex.
thermoregulation: Maintenance of internal
body temperature regardless of environmental
temperature.
ubiquitous: Seeming to be everywhere.
ultradian rhythm: A perodicity of less than 24
hours.
unihemispheric sleep: A type of sleep in which
one side of the brain is asleep while the other is
awake. This phenomenon is observed most
notably in birds (like those that make long,
transoceanic flights) and aquatic mammals (like
dolphins and porpoises).
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