718
Glossary
afterbirth
placenta and associated membranes
expelled from uterus after delivery of infant
afterhyperpolarization
decrease in membrane
potential in neurons at the end of the action
potential
afterload
the work the heart does while ejecting
blood; a function of the arterial blood pressure,
as well as the diameter and thickness of the
ventricles
agonist
(AG-ah-nist) chemical messenger that
binds to receptor and triggers cell’s response;
often refers to drug that mimics action of
chemical normally in the body
airway
tube through which air fl ows between
external environment and lung alveoli
albumin
(al-BU-min) most abundant plasma
protein
aldosterone
(al-doh-STEER-own or al-DOS-
stir-own) mineralocorticoid steroid hormone
secreted by adrenal cortex; regulates electrolyte
balance
alkaline solution
any solution having H
+
concentration lower than that of pure water
(that is, having a pH greater than 7)
alkalosis
(alk-ah-LOH-sis) any situation in which
arterial blood H
+
concentration is reduced
below normal resting levels;
see also
metabolic
alkalosis, respiratory alkalosis
all-or-none
pertaining to event that occurs
maximally or not at all
allosteric modulation
(al-low-STAIR-ik) control
of protein binding site properties by modulator
molecules that bind to regions of the protein
other than the binding site altered by them
allosteric protein
protein whose binding
site characteristics are subject to allosteric
modulation
alpha-adrenergic receptor
one type of
plasma-membrane receptor for epinephrine
and norepinephrine; also called alpha
adrenoceptor;
compare
beta-adrenergic
receptor
alpha cell
glucagon-secreting cell of pancreatic
islets of Langerhans
alpha-glycerol phosphate
three-carbon molecule
that combines with fatty acids to form
triglyceride; also called glycerol 3-phosphate
alpha helix
coiled regions of proteins or DNA
formed by hydrogen bonds
`
-ketoacid
(AL-fuh KEY-toh) molecule formed
from amino acid metabolism and containing
carbonyl (—CO—) and carboxyl (—COOH)
groups
alpha motor neuron
motor neuron that
innervates extrafusal skeletal muscle fi bers
alpha rhythm
prominent 8- to 13-Hz oscillation
on the electroencephalograms of awake,
relaxed adults with their eyes closed
alternate complement pathway
sequence for
complement activation that bypasses fi rst
steps in classical pathway and is not antibody
dependent
alveolar dead space
(al-VEE-oh-lar) volume of
fresh inspired air that reaches alveoli but does
not undergo gas exchange with blood
alveolar pressure (
P
alv
)
air pressure in
pulmonary alveoli
alveolar ventilation (
V
˙
A
)
volume of atmospheric
air entering alveoli each minute
alveolus
(al-VEE-oh-lus) (lungs) thin-walled,
air-fi lled “outpocketing” from terminal air
passageways in lungs; (glands) cell cluster at
end of duct in secretory gland
amacrine cell
(AM-ah-krin) a specialized type
of neuron found in the retina of the eye
that integrates information between local
photoreceptor cells
amine hormone
(ah-MEEN) hormone derived
from amino acid tyrosine; includes thyroid
hormones, epinephrine, norepinephrine, and
dopamine
amino acid
(ah-MEEN-oh) molecule containing
amino group, carboxyl group, and side chain
attached to a carbon atom; molecular subunit
of protein
amino acid side chain
the variable portions
of amino acids; may contain acidic or basic
charged regions, or may be hydrophobic
amino group
—NH
2
; ionizes to —NH
3
+
aminopeptidase
(ah-meen-oh-PEP-tih-dase) one
of a family of enzymes located in the intestinal
epithelial membrane; breaks peptide bond at
amino end of polypeptide
ammonia
NH
3
; produced during amino acid
breakdown; converted in liver to urea; ionized
form is ammonium
amnion
another term for amniotic sac
amniotic cavity
(am-nee-AHT-ik) fl uid-fi lled
space surrounding the developing fetus
enclosed by amniotic sac
amniotic fl
uid
liquid within amniotic cavity that
has a composition similar to extracellular fl uid
amniotic sac
membrane surrounding fetus
in
utero
AMPA receptor
receptor protein found in the
membrane of some brain neurons, named
for its binding to alpha-amino-3 hydroxy-5
methyl-4 isoxazole proprionic acid
amphipathic
(am-fuh-PATH-ik) a molecule
containing polar or ionized groups at one end
and nonpolar groups at the other
ampulla
structure in the wall of the semicircular
canals containing hair cells that respond to
head movement
amylase
(AM-ih-lase) enzyme that partially breaks
down polysaccharides
anabolism
(an-NAB-oh-lizm) cellular synthesis of
organic molecules
anaerobic
(an-ih-ROH-bik) in the absence of
oxygen
anatomic dead space
space in respiratory tract
airways where gas exchange does not occur
with blood
androgen
(AN-dro-jen) any hormone with
testosterone-like actions
androgen-binding protein
synthesized and
secreted by Sertoli cell of the testes—binds to
and increases local testosterone concentration
in fl uid in the seminiferous tubule
anemia
(ah-NEE-me-ah) reduction in total blood
hemoglobin
angiogenesis
(an-gee-oh-JEN-ah-sis) the
development and growth of capillaries;
stimulated by angiogenic factors
angiogenic factor
chemical signal that induces
the development and growth of blood vessels
angiotensin I
small polypeptide generated in
plasma by renin’s action on angiotensinogen
angiotensin II
hormone formed by action of
angiotensin-converting enzyme on angiotensin
I; stimulates aldosterone secretion from adrenal
cortex, vascular smooth-muscle contraction,
and thirst
angiotensin-converting enzyme (ACE)
enzyme
on capillary endothelial cells that catalyzes
removal of two amino acids from angiotensin I
to form angiotensin II
angiotensinogen
(an-gee-oh-ten-SIN-oh-gen)
plasma protein precursor of angiotensin I;
produced by liver
anion
(AN-eye-on) negatively charged ion;
compare
cation
antagonist
(muscle) muscle whose action opposes
intended movement; (drug) molecule that
competes with another for a receptor and binds
to the receptor but does not trigger the cell’s
response
anterior
toward or at the front
anterior pituitary
anterior portion of pituitary
gland; synthesizes, stores, and releases ACTH,
GH, TSH, prolactin, FSH, and LH
anterograde
(AN-ter-oh-grayd) movement of a
substance or action potential in the forward
direction from a neuron’s dendrites and/or cell
body, toward the axon terminal
anterolateral pathway
ascending neural pathway
running in the anterolateral column of the
spinal cord white matter; conveys information
about pain and temperature
antibody
(AN-tih-bah-dee) immunoglobulin
secreted by plasma cell; combines with type of
antigen that stimulated its production; directs
attack against antigen or cell bearing it
antibody-dependent cellular cytotoxicity
(ADCC)
killing of target cells by toxic
chemicals secreted by NK cells; the target cells
are linked to the NK cells by antibodies
antibody-mediated response
humoral immune
response mediated by circulating antibodies;
major defense against microbes and toxins in
the extracellular fl uid
anticodon
(an-tie-KOH-don) three-nucleotide
sequence in tRNA able to base-pair with
complementary codon in mRNA during
protein synthesis
antidiuretic hormone (ADH)
(an-ty-dy-yor-
ET-ik)
see
vasopressin
antigen
(AN-tih-jen) any foreign molecule that
stimulates a specifi c immune response
antigen binding site
one of the two variable
“prongs’’ on an immunoglobulin capable of
binding to a specifi c antigen
antigen presentation
process by which an
antigen-presenting cell, such as a macrophage,
combines proteolytic fragments of a foreign
antigen with host cell class II MHC proteins,
which are transported to the host cell’s surface
antigen-presenting cell (APC)
cell that presents
antigen, complexed with MHC proteins on its
surface, to T cells
antithrombin III
a plasma protein activated
by heparin that limits clot formation by
inactivating thrombin and other clotting factors
antrum
(AN-trum) (gastric) lower portion of
stomach (that is, region closest to pyloric
sphincter); (ovarian) fl uid-fi lled cavity in
maturing ovarian follicle
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