Glossary
733
metabolism
(meh-TAB-uhl-izm) chemical
reactions that occur in a living organism
metabolite
(meh-TAB-oh-lite) substance
produced by metabolism
metabolize
change by chemical reactions
metabotropic receptor
(meh-tab-oh-TRO-pik)
membrane receptor in neurons that initiates
formation of second messengers when bound
with ligand
metarteriole
(MET-are-teer-ee-ole) blood vessel
that directly connects arteriole and venule
methyl group
—CH
3
MHC protein
plasma-membrane protein coded
for by a major histocompatibility complex;
restricts T-cell receptor’s ability to combine
with antigen on cell; categorized as class I and
class II
micelle
(MY-sell) soluble cluster of amphipathic
molecules in which molecules’ polar regions
line surface and nonpolar regions orient
toward center; formed from fatty acids,
monoglycerides, and bile salts during fat
digestion in small intestine
microbe
bacterium, virus, fungus, or other
parasite
microcirculation
blood circulation in arterioles,
capillaries, and venules
microfi
lament
rodlike cytoplasmic actin fi lament
that forms major component of cytoskeleton
microglia
a type of glial cell that acts as a
macrophage
microtubule
tubular cytoplasmic fi lament
composed of the protein tubulin; provides
internal support for cells and allows change in
cell shape and organelle movement in cell
microvillus
(my-kroh-VIL-us) small fi ngerlike
projection from epithelial-cell surface; greatly
increase surface area of cell; characteristic of
epithelium lining small intestine and kidney
nephrons
micturition
(mik-chur-RISH-un) urination
midbrain
the most rostral section of the brainstem
middle ear
air-fi lled space in temporal bone;
contains three ear bones that conduct sound
waves from tympanic membrane to cochlea
migrating myoelectric complex (MMC)
pattern
of peristaltic waves that pass over small
segments of intestine after absorption of meal
milk ejection refl
ex
process by which milk is
moved from mammary gland alveoli into ducts,
from which it can be sucked; due to oxytocin
milliliter (ml)
(MIL-ih-lee-ter) volume equal to
0.001 L
millimol (mmol)
(MIL-ih-mole) amount equal
to 0.001 mol
millivolt (mV)
(MIL-ih-volt) electrical potential
equal to 0.001 V
mineral
inorganic substance (that is, without
carbon); major minerals in body are calcium,
phosphorus, potassium, sulfur, sodium,
chloride, and magnesium
mineralization
the process of calcifying bone
collagen to form lamellar bone
mineralocorticoid
(min-er-al-oh-KORT-ih-koid)
steroid hormone produced by adrenal cortex;
has major effect on sodium and potassium
balance; major mineralocorticoid is aldosterone
minute ventilation
total ventilation per minute;
equals tidal volume times respiratory rate
mitochondrion
(my-toh-KON-dree-un) rod-
shaped or oval cytoplasmic organelle that
produces most of cell’s ATP; site of Krebs cycle
and oxidative phosphorylation enzymes
mitogen
(MY-tuh-jen) chemical that stimulates
cell division
mitosis
(my-TOH-sis) process in cell division in
which DNA is duplicated and copies of each
chromosome are passed to daughter cells as the
nucleus divides
mitral valve
(MY-tral) valve between left atrium
and left ventricle of heart
M line
transverse stripe occurring at the center
of the A band in cardiac and skeletal muscle;
location of energy-generating enzymes and
proteins connecting adjacent thick fi laments
modality
(moh-DAL-ih-tee) type of sensory
stimulus
modulation
see
allosteric modulation, covalent
modulation
modulator molecule
ligand that, by acting at
an allosteric regulatory site, alters properties
of other binding sites on a protein and thus
regulates its functional activity
mol
weight of a substance in grams equal to its
molecular weight; 1 mol = 6 × 10
23
molecules
molarity
(moh-LAR-ih-tee) number of moles of
solute per liter of solution
molecular weight
sum of atomic weights of all
atoms in molecule
molecule
chemical substance formed by linking
atoms together
monoamine oxidase (MAO)
enzyme that breaks
down catecholamines in nerve terminal and
synapse
monocyte
(MAH-noh-site) type of leukocyte;
leaves bloodstream and is transformed into a
macrophage
monoglyceride
(mah-noh-GLISS-er-ide) glycerol
linked to one fatty acid side chain
monoiodotyrosine
a singly iodinated tyrosine
molecule that is an intermediate in the
synthesis of thyroid hormones
monosaccharide
(mah-noh-SAK-er-ide)
carbohydrate consisting of one sugar molecule,
which generally contains fi ve or six carbon
atoms
monosynaptic refl
ex
(mah-noh-sih-NAP-tik)
refl ex in which the afferent neuron directly
activates motor neurons
monounsaturated fatty acid
a fatty acid,
such as oleic acid, in which one carbon-
carbon double bond is formed within the
hydrocarbon chain due to the removal of two
hydrogen atoms
mood
a long-term inner emotion that affects how
individuals perceive their environment
motilin
(moh-TIL-in) candidate intestinal
hormone thought to control normal GI motor
activity
motility, gastric
movement of the gastrointestinal
tract mediated by muscular contractions
motivation
see
primary motivated behavior
motor
having to do with muscles and movement
motor control hierarchy
brain areas having a
role in skeletal muscle control are rank-ordered
in three functional groups
motor control system
CNS parts that contribute
to control of skeletal muscle movements
motor cortex
strip of cerebral cortex along
posterior border of frontal lobe; gives rise to
many axons descending in corticospinal and
multineuronal pathways; also called
primary
motor cortex
motor end plate
specialized region of muscle cell
plasma membrane that lies directly under axon
terminal of a motor neuron
motor neuron
somatic efferent neuron, which
innervates skeletal muscle
motor neuron pool
all the motor neurons for a
given muscle
motor program
pattern of neural activity required
to perform a certain movement
motor unit
motor neuron plus the muscle fi bers
it innervates
mouth
general term for the expanded uppermost
portion of the digestive tract
mucosa
(mu-KOH-sah) three layers of
gastrointestinal tract wall nearest lumen—that
is,
epithelium, lamina propria,
and
muscularis
mucosa
Müllerian duct
(mul-AIR-ee-an) part of
embryo that, in a female, develops into
reproductive system ducts, but in a male,
degenerates
Müllerian-inhibiting substance (MIS)
protein
secreted by fetal testes that causes Müllerian
ducts to degenerate
multimeric protein
a protein in which two or
more proteins are associated via hydrogen
bonds, hydrophobic attractions, and other
forces, to yield a single, larger protein
multineuronal pathway
pathway made up
of chains of neurons functionally connected
by synapses; also called
multisynaptic
pathway
multiunit smooth muscle
smooth muscle
that exhibits little, if any, propagation of
electrical activity from fi ber to fi ber and whose
contractile activity is closely coupled to its
neural input
muscarinic receptor
(mus-kur-IN-ik)
acetylcholine receptor that responds to the
mushroom poison muscarine; located on
smooth muscle, cardiac muscle, some CNS
neurons, and glands
muscle
number of muscle fi bers bound together
by connective tissue
muscle cell
specialized cell containing actin and
myosin fi laments and capable of generating
force and movement
muscle fatigue
decrease in muscle tension with
prolonged activity
muscle fi
ber
muscle cell
muscle spindle
a receptor organ, made up of
specialized muscle fi bers, that detects stretch of
skeletal muscles
muscle-spindle stretch receptor
capsule-
enclosed arrangement of afferent nerve fi ber
endings around specialized skeletal muscle
fi bers; sensitive to stretch
muscle tension
force exerted by a contracting
muscle on object
muscle thick fi
lament
see
thick fi lament
muscle tissue
one of the four major tissue types
in the body, comprising smooth, cardiac, and
skeletal muscle; can be under voluntary or
involuntary control
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