glossary G-5attachment sites for microtubules that help move the chromo-
some during nuclear division.
cerebellum (ser-ah-bell-um) [L. diminutive of cerebrum,
brain] Hindbrain region with reflex centers for maintaining
posture and refining limb movements.
cerebral cortex Thin surface layer of the cerebral hemi-
spheres. Some regions of the cortex receive sensory input,
others integrate information and coordinate appropriate
motor responses.
cerebral hemispheres The left and right sides of the
cerebrum, which are separated by a deep fissure.
cerebrospinal fluid CSF; clear extracellular fluid that sur-
rounds and cushions the brain and spinal cord.
cerebrum (suh-ree-bruhm) Part of the forebrain; the most
complex integrating center.
cervix The lower part of the uterus.
chemical bond A union between the electron structures of
two or more atoms.
chemical energy The potential energy of molecules.
chemical equilibrium The point at which a reversible reac-
tion will be running at about the same pace in both directions.
chemical senses Senses, such as taste and smell, that
detect substances dissolved in fluid that is in contact with
chemoreceptors.
chemical synapse (sin-aps) [Gk. synapsis, union] A small
gap, the synaptic cleft, that separates two neurons (or a neu-
ron and a muscle cell or gland cell) and that is bridged by
neurotransmitter molecules released from the presynaptic
neuron.
chemoreceptor (kee-moe-ree-sep-tur) Sensory receptor that
detects chemical energy (ions or molecules) dissolved in the
surrounding fluid.
chemotherapy The use of therapeutic drugs to kill cancer
cells.
chlorofluorocarbon (CFC) (klore-oh-floor-oh-car-bun) One
of a variety of odorless, invisible compounds of chlorine, fluo-
rine, and carbon, widely used in commercial products, that
are contributing to the destruction of the ozone layer above
Earth’s surface.
chorion (core-ee-on) One of four extraembryonic mem-
branes; it encloses the embryo and the three other mem-
branes. Absorptive structures (villi) that develop at its surface
are crucial for the transfer of substances between the embryo
and mother.
chorionic villus sampling (CVS) Test of fetal cells removed
from chorionic villi for evidence of birth defects.
chromatid See sister chromatids.
chromatin A cell’s DNA and all of the proteins associated
with it.
chromosome (crow-moe-soam) [Gk. chroma, color, and soma,
body] A double-stranded DNA molecule that carries genetic
information.cardiac pacemaker Sinoatrial (SA) node; the source of the
normal rate of heartbeat. The self-excitatory cardiac muscle
cells that spontaneously generate rhythmic waves of excita-
tion over the heart chambers.
cardiovascular system Organ system that is composed of
the heart and blood vessels and that functions in the rapid
transport of blood to and from tissues.
carotid artery Artery in the neck that contains baroreceptors,
which monitor arterial pressure.
carotid body Any of several sensory receptors that moni-
tor carbon dioxide and oxygen levels in blood; located at the
point where carotid arteries branch to the brain.
carrying capacity The maximum number of individuals in a
population (or species) that can be sustained indefinitely by a
given environment.
cartilage A type of connective tissue with solid yet pliable
intercellular material that resists compression.
cartilaginous joint Type of joint in which cartilage fills the
space between adjoining bones; only slight movement is
possible.
catabolism Metabolic activity that breaks down large
molecules into simpler ones, releasing the components for use
by cells.
cell [L. cella, small room] The smallest living unit; an orga-
nized unit that can survive and reproduce on its own, given
DNA instructions and suitable environmental conditions,
including appropriate sources of energy and raw materials.
cell cycle Events during which a cell increases in mass,
roughly doubles its number of cytoplasmic components,
duplicates its DNA, then undergoes nuclear and cytoplasmic
division. It extends from the time a new cell is produced until
it completes its own division.
cell differentiation The gene-guided process by which cells
in different locations in the embryo become specialized.
cell-mediated immune response The T cell defensive
response to pathogens in the body, wherein cytotoxic T cells
attack the invaders directly.
cell theory A fundamental theory in biology that states
that (1) all organisms are composed of one or more cells,
(2) the cell is the smallest unit that still retains a capacity
for independent life, and (3) all cells arise from pre-existing
cells.
cell-to-cell junction A point of contact that physically links
two cells or that provides functional links between their
cytoplasm.
cellular respiration The process by which cells break apart
carbohydrates, lipids, or proteins to form ATP.
central nervous system The brain and spinal cord.
centriole (sen-tree-ohl) A cylinder of triplet microtubules
that gives rise to the microtubules of cilia and flagella.
centromere (sen-troh-meer) [Gk. kentron, center, and meros,
a part] A small, constricted region of a chromosome having
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