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

Glossary
amplitude: Magnitude, greatness of size.
anesthesia: Complete or partial loss of sensation,
usually caused by artificially produced unconsciousness.
biological clock: A collection of cells that regulates
an overt biological rhythm, such as the
sleep/wake cycle, or some other aspect of biological
timing, including reproductive cycles or hibernation.
cataplexy: Sudden muscle weakness associated
with narcolepsy. It is often triggered by emotions
such as anger, surprise, laughter, and exhilaration.
cerebral cortex: The brain’s outer layer of gray
tissue that is responsible for higher nervous
function.
circadian: Exhibiting a periodicity of 24 hours.
cyanobacteria: Blue-green algae.
cytokines: Molecules that regulate the functioning
of the immune system.
cytoplasm: Protoplasm outside a cell nucleus.
delta waves: Brain waves with a frequency of 1 to
3 hertz that emanate from the forward portion of
the brain during deep sleep in normal adults.
desynchronization: Lack of alignment between
external signals and the biological clock.
diurnal: Active or occurring during the daytime;
repeating once each 24 hours.
electroencephalogram (EEG): A measurement
of the electrical activity associated with brain
activity.
electromyogram (EMG): A measurement of the
electrical activity associated with muscle movements.
electrooculogram (EOG): A measurement of the
electrical activity associated with eye movements.
endocrine system: The ductless glands in the
body that secrete hormones.
endogenous rhythms: Rhythms driven by an
internal, self-sustaining biological clock rather
than by signals that are external to the organism
(for example, light).
endothermic animals: Animals that expend
energy to maintain body temperature.
entrain: To reset or align with the biological clock.
enuresis: Bed-wetting.
exacerbate: To aggravate or increase the severity of.
exogenous rhythms: A rhythm that is directly regulated
by an external influence, such as an environmental
cue. They are not generated internally
by the organism itself.
follicle stimulating hormone: A hormone produced
in the pituitary gland that stimulates the
growth of follicles in the ovary and induces spermatogenesis
in the testes.
frequency: The number of times a periodic
process occurs per unit of time.
hallucination: A false and distorted perception of
objects or events.
homeostasis: The ability or tendency of an organism
or cell to maintain internal equilibrium by
adjusting its internal processes.
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