Encyclopedia of Biology

hypotonic solution 171

cancerous) enlargement of the prostate gland, common
in older men.

hyperpolarization An electrical state where the
inside of a cell is made more negative relative to the
outside than was the case at its resting potential of
about –70 mV.

hypertonic solution Asolution whose solute con-
centration is high enough to cause water to move out
of cells via osmosis.

hypertrophy Acondition where an organ or tissue
enlarges or overgrows due to an increase in the size of
its cells, not the number of cells.

hyperventilate The act of excessive breathing,
causing a loss of carbon dioxide in the blood. Other
symptoms include faintness or fainting and numbness
around the mouth, fingertips, or toes.

hypha The threadlike, filamentous, absorptive struc-
tures of fungi. When combined to form mats, they are
called mycelia and are the main body of fungi.

hypogynous ovary(superior ovary) Ovaries that

have the calyx, corolla, and androecium attached

below the ovary to the receptacle.

hypoosmotic solution A solution whose osmotic

pressure is less than that of another solution.

hypothalamus An area in the posterior part of

the brain beneath the thalamus that contains nerve

cells and controls many autonomic functions. Con-

trols the pituitary gland and is the control site for

feeding, drinking, temperature regulation, emotion,

and motivation.

hypothesis The formal declaration of the possible

explanation of a set of observations that needs to be

tested and proved.

hypotonic solution A solution where solute concen-

tration is low enough to cause water to move into cells

via osmosis.