G-1adipose (ad 9 ̆ı-pˉos) tissue Fatty tissue. A type of
connective tissue consisting of fat cells in a loose
connective tissue matrix.
ADP adenosine diphosphate ( ̆a-den 9 ̆o-s ̄en
di-fos 9 f ̄at). A molecule that, together with inorganic
phosphate, is used to make ATP (adenosine
triphosphate).
adrenal cortex ( ̆a-dre 9 nal kor 9 teks) The outer
part of the adrenal gland. Derived from embryonic
mesoderm, the adrenal cortex secretes corticosteroid
hormones, including aldosterone and hydrocortisone.
adrenal medulla (m ̆edul 9 ̆a) The inner part
of the adrenal gland. Derived from embryonic
postganglionic sympathetic neurons, the adrenal
medulla secretes catecholamine hormones—
epinephrine and (to a lesser degree) norepinephrine.
adrenergic (ad 0 r ̆e-ner 9 jik) Denoting the actions
of epinephrine, norepinephrine, or other molecules
with similar activity (as in adrenergic receptor and
adrenergic stimulation).
aerobic ( ̆a-ro 9 bik) capacity The ability of an
organ to utilize oxygen and respire aerobically to
meet its energy needs.
aerobic ( ̆a-ro 9 bik) cell respiration The metabolic
pathways that provide electrons for the electron
transport system in the mitochondrial cristae,
and provide protons for the formation of ATP by
oxidative phosphorylation in the mitochondria. Cells
obtain most of their ATP by aerobic cell respiration.
afferent (af 9 er-ent) Conveying or transmitting
inward, toward a center. Afferent neurons, for
example, conduct impulses toward the central
nervous system; afferent arterioles carry blood
toward the glomerulus.
afterload Related to the total peripheral resistance
and arterial pressure, the afterload pre sents an
impedance to the ejection of blood from the
ventricles at systole.
agglutinate ( ̆a-gloot 9 n- ̄at) A clumping of cells
(usually erythrocytes) as a result of specific chemical
interaction between surface antigens and antibodies.
agonist (ag 9 on-ist) Regarding muscles, an agonist
is a muscle that performs a particular action that
is opposed by one or more antagonistic muscles.
Regarding regulatory molecules and drugs, an
agonist is a molecule that specifically binds to and
activates a particular receptor protein; antagonistic
molecules may block the ability of the agonist to
activate the receptor protein.
agouti (ah-gu 9 te)-related protein Abbreviated
AgRP, this is a neuropeptide released by neurons in
the hypothalamus that, together with neuropeptide Y,
promotes hunger (is orexigenic).
agranular leukocytes (a-gran 9 y ̆u-lar loo 9 k ̆o-s ̄ıts)
White blood cells (leukocytes) with cytoplasmic
granules that are too small to be clearly visible;
specifically, lymphocytes and monocytes.
albumin (al-byoo 9 min) A water-soluble protein
produced in the liver; the major component of the
plasma proteins.
aldosterone (al-dos 9 ter- ̆on) The principal
corticosteroid hormone involved in the regulation of
electrolyte balance (mineralocorticoid).
alkalosis (al 0 k ̆a-lo 9 sis) An abnormally high
alkalinity of the blood and body fluids (blood
pH > 7.45).acidosis (as 0 ̆ı-do 9 sis) An abnormal increase in the
H^1 concentration of the blood that lowers arterial pH
below 7.35.
acromegaly (ak 0 ro-meg 9 ̆a-le) A condition
caused by hypersecretion of growth hormone from
the pituitary after maturity and characterized by
enlargement of the extremities, such as the nose,
jaws, fingers, and toes.
acrosome (ak 9 ro-som) The membranous cap on
the head of a sperm that contains digestive enzymes.
During fertilization, an acrosomal reaction releases
these enzymes so that the sperm can tunnel through
the zona pellucida and reach the plasma membrane
of the oocyte.
ACTH adrenocorticotropic ( ̆a-dre 0 no-kor 0 ̆a-
ko-trop 9 ik) hormone. A hormone secreted by the
anterior pituitary that stimulates the adrenal cortex.
actin (ak 9 tin) A structural protein of muscle
that, along with myosin, is responsible for muscle
contraction.
action potential An all-or-none electrical event
in an axon or muscle fiber in which the polarity
of the membrane potential is rapidly reversed and
reestablished.
active immunity Immunity involving sensitization,
in which antibody production is stimulated by prior
exposure to an antigen.
active transport The movement of molecules or
ions across the cell membranes of epithelial cells by
membrane carriers. An expenditure of cellular energy
(ATP) is required.
adaptive immunity Also called specific immunity;
the ability of lymphocytes to react to specific
molecular targets, or antigens, and to respond to
these targets more effectively after prior exposure
to them.
adaptive thermogenesis (ther 0 mo-jen 9 e-sis) The
heat energy expended in response to changes in
ambient temperature and during the digestion and
absorption of food.
adenohypophysis (ad 0 n-o-hi-pof 9 ̆ı-sis)
The anterior, glandular lobe of the pituitary gland
that secretes FSH (follicle-stimulating hormone), LH
(luteinizing hormone), ACTH (adrenocorticotropic
hormone), TSH (thyroid-stimulating hormone),
GH (growth hormone), and prolactin. Secretions of
the anterior pituitary are controlled by hormones
secreted by the hypothalamus.
adenylate cyclase ( ̆a-den 9 l-it si 9 kl ̄ase) An
enzyme found in cell membranes that catalyzes
the conversion of ATP to cyclic AMP and
pyrophosphate (PP 1 ). This enzyme is activated by
an interaction between a specific hormone and its
membrane receptor protein.
ADH antidiuretic (an 0 te-di 0 y ̆u-ret 9 ik) hormone,
also known as vasopressin. A hormone produced by
the hypothalamus and released from the posterior
pituitary. It acts on the kidneys to promote water
reabsorption, thus decreasing the urine volume.
adipokines (ad 9 i-po-kins 0 ) Hormones (including
leptin, adiponectin, resistin, and others) secreted by
adipose cells.
adiponectin (ad-i-po-nek 9 tin) A hormone secreted
by adipose tissue that stimulates glucose utilization
and fatty acid oxidation. Its secretion is decreased in
obesity and type 2 diabetes mellitus.Glossary
Keys to Pronunciation
Most of the words in this glossary are fol-
lowed by a phonetic spelling that serves as a
guide to pronunciation. The phonetic spell-
ings reflect standard scientific usage and can
be interpreted easily following a few basic
rules.- Any unmarked vowel that ends a
syllable or that stands alone as a
syllable has the long sound. For
example, ba, ma, and na rhyme with
fay; be, de, and we rhyme with fee;
bi, di, and pi rhyme with sigh; bo, do,
and mo rhyme with go. Any unmarked
vowel that is followed by a consonant
has the short sound (for example, the
vowel sounds in hat, met, pit, not, and
but). - If a long vowel appears in the middle of
a syllable (followed by a consonant), it
is marked with a macron ( ̄). Similarly,
if a vowel stands alone or ends a
syllable but should have a short sound,
it is marked with a breve ( ̆). - Syllables that are emphasized are
indicated by stress marks. A single
stress mark ( 9 ) indicates the primary
emphasis; a secondary emphasis is
indicated by a double stress mark ( 0 ).
A
ABO system The most common system of
classification for red blood cell antigens. On the basis
of antigens on the red blood cell surface, individuals
can be type A, type B, type AB, or type O.
absorption (ab-sorp 9 shun) The transport of
molecules across epithelial membranes into the body
fluids.
accommodation ( ̆a-kom 0 ̆o-da 9 shun) Adjustment;
specifically, the process whereby the focal length of
the eye is changed by automatic adjustment of the
curvature of the lens to bring images of objects from
various distances into focus on the retina.
acetyl (as 9 ̆ı-tl, ̆a-s ̄et 9 l) CoA (Acetyl coenzyme A)
An intermediate molecule in aerobic cell respiration
that, together with oxaloacetic acid, begins the Krebs
cycle. Acetyl CoA is also an intermediate in the
synthesis of fatty acids.
acetylcholine ( ̆a-s ̄et 0 l-ko 9 l ̄en) (ACh) An acetic
acid ester of choline—a substance that functions as
a neurotransmitter chemical in somatic motor nerve
and parasympathetic nerve fibers.
acetylcholinesterase ( ̆a-s ̄et 0 l-ko 0 l ̆ı-nes 9 t ̆e-r ̄as)
(AChE) An enzyme in the membrane of postsynaptic
cells that catalyzes the conversion of ACh into
choline and acetic acid. This enzymatic reaction
inactivates the neurotransmitter.fox36375_glo_G1-G19.indd 1fox36375_glo_G1-G19.indd 1 2/4/15 12:29 PM2/4/15 12:29 PM