Glossary
723
corticosteroid
(kor-tih-koh-STEER-oid) steroid
produced by adrenal cortex or drug that
resembles one
corticotropin-releasing hormone (CRH)
(kor-tih-koh-TROH-pin) hypophysiotropic
peptide hormone that stimulates ACTH
(corticotropin) secretion by anterior pituitary
cortisol
(KOR-tih-sol) main glucocorticoid
steroid hormone secreted by adrenal
cortex; regulates various aspects of organic
metabolism
costimulus
nonspecifi c interactions between
proteins on the surface of antigen-presenting
cells and helper T cells; required for T cell
activation
cotransmitter
chemical messenger released
with a neurotransmitter from synapse or
neuroeffector junction
cotransport
form of secondary active transport
in which net movement of actively transported
substance and “downhill” movement of
molecule supplying the energy are in the same
direction
countercurrent multiplier system
mechanism
associated with loops of Henle that creates a
region having high interstitial fl uid osmolarity
in renal medulla
countertransport
form of secondary active
transport in which net movement of actively
transported molecule is in direction opposite
“downhill” movement of molecule supplying
the energy
covalent bond
(koh-VAY-lent) chemical bond
between two atoms in which each atom shares
one of its electrons with the other
covalent modulation
alteration of a protein’s
shape, and therefore its function, by the
covalent binding of various chemical groups
to it
cranial nerve
one of 24 peripheral nerves (12
pairs) that join brainstem or forebrain with
structures outside CNS
C-reactive protein
an acute phase protein that
functions as a nonspecifi c opsonin
creatine phosphate (CP)
(KREE-ah-tin)
molecule that transfers phosphate and energy
to ADP to generate ATP
creatinine
(kree-AT-ih-nin) waste product
derived from muscle creatine
creatinine clearance (
C
cr
)
plasma volume from
which creatinine is removed by the kidneys per
unit time; approximates glomerular fi ltration
rate
cristae (mitochondrial)
the inner membrane
of mitochondria, which may assume sheetlike
or tubular appearances; site containing
cytochrome P450 enzymes involved in steroid
hormone production
critical period
time during development when
a system is most readily infl uenced by factors,
sometimes irreversibly
cross-bridge
in muscle, myosin projection
extending from thick fi lament and capable of
exerting force on thin fi lament, causing the
fi laments to slide past each other
cross-bridge cycle
sequence of events between
binding of a cross-bridge to actin, its release,
and reattachment during muscle contraction
crossed-extensor refl
ex
increased activation
of extensor muscles contralateral to limb
exion
crossing-over
process in which segments of
maternal and paternal chromosomes exchange
with each other during chromosomal pairing
in meiosis
crystalloid
low molecular weight solute
C3b
a complement molecule that attaches
phagocytes to microbes
cumulus oophorous
layers of granulosa cells
that surround the egg within the dominant
follicle
cupula
a gelatinous mass within the semicircular
canals that contains stereocilia and responds
to head movement
current
movement of electric charge; in
biological systems, this is achieved by ion
movement
cusp
a fl ap or “leafl et” of a heart valve
cutaneous
(cue-TAY-nee-us) pertaining to skin
cyclic AMP (cAMP)
cyclic 3´,5´-adenosine
monophosphate; cyclic nucleotide that
serves as a second messenger for many “fi rst”
chemical messengers
cyclic AMP-dependent protein kinase
(KY-nase) enzyme that is activated by cyclic
AMP and then phosphorylates specifi c
proteins, thereby altering their activity; also
called
protein kinase A
cyclic endoperoxide
eicosanoid formed from
arachidonic acid by cyclooxygenase
cyclic GMP (cGMP)
cyclic 3´,5´-guanosine
monophosphate; cyclic nucleotide that acts as
second messenger in some cells
cyclic GMP-dependent protein kinase
(KY-nase) enzyme that is activated by cyclic
GMP and then phosphorylates specifi c
proteins, thereby altering their activity; also
called
protein kinase G
cyclooxygenase (COX)
(sy-klo-OX-ah-jen-ase)
enzyme that acts on arachidonic acid and
initiates production of cyclic endoperoxides,
prostaglandins, and thromboxanes
cytochrome
(SY-toh-krom) one of a series
of enzymes that couples energy to ATP
formation during oxidative phosphorylation
cytochrome P450
enzyme that mediates
hydroxylation reactions in the biosynthesis of
steroid hormones
cytokine
(SY-toh-kine) general term for protein
extracellular messengers that regulate
immune responses; secreted by macrophages,
monocytes, lymphocytes, neutrophils, and
several nonimmune cell types
cytoplasm
(SY-toh-plasm) region of cell interior
outside the nucleus
cytosine (C)
(SY-toh-seen) pyrimidine base in
DNA and RNA
cytoskeleton
cytoplasmic fi lamentous network
associated with cell shape and movement
cytosol
(SY-toh-sol) intracellular fl uid that
surrounds cell organelles and nucleus
cytotoxic T cell
(SY-toh-TOX-ik) T lymphocyte
that, upon activation by specifi c antigen,
directly attacks a cell bearing that type of
antigen and destroys it; major killer of virus-
infected and cancer cells
D
Dalton’s law
pressure exerted by each gas in a
mixture of gases is independent of the pressure
exerted by the other gases
dark adaptation
process by which photoreceptors
in the retina adjust to darkness
daughter cell
one of the two new cells formed
when a cell divides
dead space
volume of inspired air that cannot be
exchanged with blood;
see also
alveolar dead
space, anatomic dead space
deamination
see
oxidative deamination
declarative memory
memories of facts and events
decremental
decreasing in amplitude
decussation
(dek-uh-SAY-shun) crossover of
neuronal pathways from one side of the body
to the other
defecation
(def-ih-KAY-shun) expulsion of feces
from rectum
defecation refl
ex
urge to extrude feces caused by
sudden distension of the walls of the rectum
dehydration
type of chemical reaction in which
two smaller molecules, such as amino acids,
are joined to form a larger molecule; a single
molecule of water is lost in the process
delta rhythm
slow-wave, high-amplitude EEG
waves associated with the deepest stages of
slow-wave sleep
dendrite
(DEN-drite) highly branched extension
of neuron cell body; receives synaptic input
from other neurons
dendritic cell
a type of immune cell with
macrophage-like properties
dense body
cytoplasmic structure to which
thin fi laments of a smooth muscle fi ber are
anchored
deoxyhemoglobin (Hb, HbH)
(dee-ox-
see-HEE-moh-gloh-bin) hemoglobin not
combined with oxygen; reduced hemoglobin
deoxyribonucleic acid (DNA)
(dee-ox-see-ry-
boh-noo-KLAY-ik) nucleic acid that stores
and transmits genetic information; consists
of double strand of nucleotide subunits that
contain deoxyribose
deoxyribose
a ribose molecule with a single
hydroxyl group removed; a component of
DNA
depolarize
to change membrane potential value
toward zero so that cell interior becomes less
negative than resting level
descending limb
(of Henle’s loop) segment of
renal tubule into which proximal tubule drains
descending pathway
neural pathways that go
from the brain down to the spinal cord
desmosome
(DEZ-moh-some) junction that
holds two cells together; consists of plasma
membranes of adjacent cells linked by fi bers,
yet separated by a 20-nm extracellular space
fi lled with a cementing substance
detrusor muscle
(duh-TRUSS-or) the smooth
muscle that forms the wall of the urinary
bladder
developmental acclimatization
potentially
irreversible change in structure or function
of one or more organ systems that occurs
during early life and favors survival in specifi c
environments
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