Glossary G-3calcitonin (kal 0 s ̆ı-to 9 nin) Also called thyrocalci-
tonin. A polypeptide hormone produced by the
parafollicular cells of the thyroid and secreted in
response to hypercalcemia. It acts to lower
blood calcium and phosphate concentrations and
may serve as an antagonist of parathyroid
hormone.
calcium release channels These are proteins in the
membrane of the sarcoplasmic reticulum that allow
Ca^21 to diffuse down its concentration gradient, out
of the cisternae into the cytoplasm.
calmodulin (kal 0 mod 9 y ̆u-lin) A receptor protein for
Ca^21 located within the cytoplasm of target cells. It
appears to mediate the effects of this ion on cellular
activities.
calorie (kal 9 ̆o-re) A unit of heat equal to the
amount of heat needed to raise the temperature of
1 gram of water by 1 8 C.
cAMP cyclic adenosine monophosphate
( ̆a-den 9 ̆o-s ̄en mon 0 o-fos 9 f ̄at) A second messenger
in the action of many hormones, including
catecholamine, polypeptide, and glycoprotein
hormones. It serves to mediate the effects of these
hormones on their target cells.
cancer A tumor characterized by abnormally
rapid cell division and the loss of specialized tissue
characteristics. This term usually refers to malignant
tumors.
capacitation (k ̆a-pas 0 ̆ı-ta 9 shun) Changes that
occur within spermatozoa in the female reproductive
tract that enable them to fertilize ova. Sperm that have
not been capacitated in the female tract cannot fertilize
ova.
capillary (kap 9 ̆ılar 0 e) The smallest vessel in the
vascular system. Capillary walls are only one cell
thick, and all exchanges of molecules between the
blood and tissue fluid occur across the capillary
wall.
capsaicin (kap-sa 9 ̆ı-sin) receptor Both an ion
channel in cutaneous sensory dendrites and a
receptor for capsaicin—the molecule in chili peppers
that causes sensations of heat and pain. In response
to a noxiously high temperature, or to capsaicin in
chili peppers, this ion channel opens, resulting in the
perception of heat and pain.
carbohydrate (kar 0 bo-hi 9 dr ̄at) An organic
molecule containing carbon, hydrogen, and oxygen
in a ratio of 1:2:1. The carbohydrate class of
molecules is subdivided into monosaccharides,
disaccharides, and polysaccharides.
carbonic anhydrase (kar-bon 9 ik an-hi 9 dr ̄as) An
enzyme that catalyzes the formation or breakdown
of carbonic acid. When carbon dioxide
concentrations are relatively high, this enzyme
catalyzes the formation of carbonic acid from CO 2
and H 2 O. When carbon dioxide concentrations are
low, the breakdown of carbonic acid to CO 2 and
H 2 O is catalyzed. These reactions aid the
transport of carbon dioxide from tissues to
alveolar air.
carboxyhemoglobin (kar-bok 0 se-he 0 m ̆oglo 9 bin)
An abnormal form of hemoglobin in which the heme
is bound to carbon monoxide.
cardiac cycle The repeating pattern of
contraction (systole) and relaxation (diastole) of
the atria and ventricles of the heart. The chambers
fill with blood during diastole and eject blood at
systole.
cardiac (kar 9 de-ak) muscle Muscle of the heart,
consisting of striated muscle cells. These cells
are interconnected, forming a mass called the
myocardium.bi- (L.) Two, twice.
bile (b ̄ıl) Fluid produced by the liver and stored in
the gallbladder that contains bile salts, bile pigments,
cholesterol, and other molecules. The bile is secreted
into the small intestine.
bile salts Salts of derivatives of cholesterol in
bile that are polar on one end and nonpolar
on the other end of the molecule. Bile salts
have detergent or surfactant effects and act
to emulsify fat in the lumen of the small intestine.
bilirubin (bil 0 ̆ı-roo 9 bin) Bile pigment derived
from the breakdown of the heme portion of
hemoglobin.
blastocyst (blas 9 t ̆o-sist) The stage of early
embryonic development that consists of an inner
cell mass, which will become the embryo, and
surrounding trophoblast cells, which will form part
of the placenta. This is the form of the embryo that
implants in the endometrium of the uterus beginning
at about the fifth day following fertilization.
blood-brain barrier The structures and cells that
selectively prevent particular molecules
in the plasma from entering the central nervous
system.
blood-testis barrier The barrier formed by
Sertoli cells around the seminiferous tubules, which
separates the antigens in the spermatogenic cells
from the immune system in the blood.
Bohr effect The effect of blood pH on the
dissociation of oxyhemoglobin. Dissociation is
promoted by a decrease in the pH.
Boyle’s law The statement that the pressure of a
given quantity of a gas is inversely proportional to
its volume.
bradycardia (brad 0 ̆ı-kar 9 de- ̆a) A slow cardiac
rate; less than sixty beats per minute.
bradykinin (brad 0 ̆ı-ki 9 nin) A short polypeptide
that stimulates vasodilation and other cardiovascular
changes.
bronchiole (brong 9 ke- ̄ol) the smallest of the air
passages in the lungs, containing smooth muscle and
cuboidal epithelial cells.
brown adipose tissue Fat (adipose) tissue
characterized by numerous mitochondria that
contain leakage channels for H^1 between the inner
and outer mitochondrial membranes. The channels
uncouple oxidative phosphorylation, increasing
metabolic rate and heat production. Brown adipose
tissue is most prevalent in newborns, but is now
believed to be physiologically important in adults as
well.
brush border enzymes Digestive enzymes that
are located in the cell membrane of the microvilli of
intestinal epithelial cells.
buffer A molecule that serves to prevent large
changes in pH by either combining with H^1 or by
releasing H^1 into solution.
bulk transport Transport of materials into a cell
by endocytosis or phagocytosis, and out of a cell by
exocytosis.
bundle of His (hiss) A band of rapidly conducting
cardiac fibers originating in the AV node and
extending down the atrioventricular septum to
the apex of the heart. This tissue conducts action
potentials from the atria into the ventricles.C
cable properties A term that refers to the ability of
neurons to conduct an electrical current. This occurs,
for example, between nodes of Ranvier, where action
potentials are produced in a myelinated fiber.autoantibody (aw 0 to-an 9 t ̆ı-bod 0 e) An antibody
that is formed in response to, and that reacts with,
molecules that are part of one’s own body.
autocrine (aw 9 t ̆o-krin) regulation A type of
regulation in which one part of an organ releases
chemicals that help to regulate another part of
the same organ. Prostaglandins, for example, are
autocrine regulators.
autonomic (aw 0 t ̆o-nom 9 ik) nervous system The
part of the nervous system that involves control of
smooth muscle, cardiac muscle, and glands. The
autonomic nervous system is subdivided into the
sympathetic and parasympathetic divisions.
autoregulation (aw 0 to-reg 9 y ̆u la 9 shun) The ability
of an organ to intrinsically modify the degree of
constriction or dilation of its small arteries and
arterioles, and thus to regulate the rate of its own
blood flow. Autoregulation may occur through
myogenic or metabolic mechanisms.
autosomal chromosomes (aw 0 to-so 9 mal kro 9 m ̆o-
s ̄omz) The paired chromosomes; those other than the
sex chromosomes.
axon (ak 9 son) The process of a nerve cell that
conducts impulses away from the cell body.
axon initial segment The region of the axon
immediately adjacent to the axon hillock where
action potentials are first produced.
axonal (ak 9 s ̆o-nal, ak-son 9 al) transport The
transport of materials through the axon of a neuron.
This usually occurs from the cell body to the end of
the axon, but retrograde (backward) transport can
also occur.B
Babinski reflex The extension of the great toe and
abduction (upward movement) of the other toes when
the sole of the foot is gently stroked, whereas normal
adults respond to this stimulation with toe flexion.
The Babinski reflex in adults can indicate damage to
the pyramidal motor tract. Also called the Babinski
sign.
B-type natriuretic (na 9 tre-u-ret 9 ik) peptide (BNP)
A hormone released by the heart’s ventricles when
they are stretched by increased blood volume. It acts
on the kidneys like atrial natriuretic peptide (ANP) to
promote diuresis. An increase in blood levels of BNP
occurs in congestive heart failure and is sometimes
used to assess this condition.
baroreceptors (bar 0 o-re-sep 9 torz) Receptors for
arterial blood pressure located in the aortic arch and
the carotid sinuses.
Barr body A microscopic structure in the cell
nucleus produced from an inactive X chromosome
in females.
basal ganglia (ba 9 sal gang 9 gle- ̆a) Gray matter, or
nuclei, within the cerebral hemispheres, forming the
corpus striatum, amygdaloid nucleus, and claustrum.
basal metabolic (ba 9 sal met 0 ̆a-bol 9 ik) rate (BMR)
The rate of metabolism (expressed as oxygen
consumption or heat production) under resting or
basal conditions 8 to 12 hours after eating.
basophil (ba 9 s ̆o-fil) The rarest type of leukocyte; a
granular leukocyte with an affinity for blue stain in
the standard staining procedure.
B cell lymphocytes (lim 9 f ̆o-s ̄ıts) Lymphocytes that
can be transformed by antigens into plasma cells
that secrete antibodies (and are thus responsible
for humoral immunity). The B stands for bursa
equivalent, which is believed to be the bone
marrow.
benign (b ̆ı-n ̄ın 9 ) Not malignant or life threatening.fox36375_glo_G1-G19.indd 3fox36375_glo_G1-G19.indd 3 2/4/15 12:29 PM2/4/15 12:29 PM