742
Glossary
substantia nigra
(sub-STAN-sha NIE-gra) a
subcortical nucleus containing dark-staining
neurons that release dopamine and are
important for suppressing extraneous muscle
activity
substrate
(SUB-strate) reactant in enzyme-
mediated reaction
substrate-level phosphorylation
(fos-for-ih-
LAY-shun) direct transfer of phosphate group
from metabolic intermediate to ADP to form
ATP
subsynaptic membrane
(sub-sih-NAP-tik)
the part of postsynaptic neuron’s plasma
membrane under synapse
subthreshold potential
(sub-THRESH-old)
depolarization less than threshold potential
subthreshold stimulus
stimulus capable of
depolarizing membrane but not by enough to
reach threshold
sucrose
(SOO-krose) disaccharide composed of
glucose and fructose; also called
table sugar
sulcus
(plural,
sulci
) a deep groove between gyri
on the surface of the cerebral cortex
sulfate
SO
4
2–
sulfhydryl group
(sulf-HY-drul) —SH
sulfuric acid
(sulf-YOR-ik) acid generated
during catabolism of sulfur-containing
compounds; dissociates to form sulfate and
hydrogen ions
summation
(sum-MAY-shun) increase in muscle
tension or shortening in response to rapid,
repetitive stimulation relative to single twitch
superior vena cava
(VEE-nah KAY-vah) large
vein that carries blood from upper half of
body to right atrium of heart
superoxide anion
potentially damaging, highly
reactive oxygen molecule containing an extra
electron
supersensitivity
increased response to a ligand
due to receptor up-regulation
supplementary motor cortex
region of the
cerebral cortex found on the medial side of
brain hemispheres in front of the primary
motor cortex; involved in planning and
enacting complex muscle movements
suprachiasmatic nucleus
group of cells in the
hypothalamus involved in production of
circadian rhythms
surface tension
attractive forces between water
molecules at an air-water interface resulting in
net force that acts to reduce surface area
surfactant
(sir-FAK-tent) detergent-like
phospholipid-protein mixture produced by
pulmonary type II alveolar cells; reduces
surface tension of fl uid fi lm lining alveoli
swallowing center
area of the medulla oblongata
in the central nervous system that receives
afferent neural input from the mouth and
sends efferent output to the muscles of the
pharynx, esophagus, and respiratory system,
coordinating swallowing
sweat gland
gland beneath the skin that is
capable of secreting a salty fl uid through ducts
to the surface of the skin in response to heat-
induced neural signals from the autonomic
nervous system
sympathetic division
portion of autonomic
nervous system whose preganglionic fi bers
leave CNS at thoracic and lumbar portions of
spinal cord;
compare
parasympathetic division
sympathetic trunk
one of paired chains of
interconnected sympathetic ganglia that lie on
either side of vertebral column
sympathomimetic
(sym-path-oh-mih-MET-
ik) produces effects similar to those of
sympathetic nervous system
synapse
(SIN-apse) anatomically specialized
junction between two neurons where
electrical activity in one neuron infl uences
excitability of second;
see also
chemical
synapse, electrical synapse, excitatory synapse,
inhibitory synapse
synaptic cleft
narrow extracellular space
separating pre- and postsynaptic neurons at
chemical synapse
synaptic delay
length of time it takes for
electrical changes to move from the
presynaptic to the postsynaptic membrane
synaptic potential
see
postsynaptic potential
synaptic vesicle
cellular structure that holds and
releases neurotransmitter at the synapse
synaptotagmin
(sin-ap-toh-TAG-min) protein
present in wall of synaptic vesicle that binds
calcium and helps stimulate the process of
exocytosis
synergistic muscle
(sin-er-JIS-tik) muscle that
exerts force to aid intended motion
systemic circulation
(sis-TEM-ik) circulation
from left ventricle through all organs except
lungs and back to heart
systole
(SIS-toh-lee) period of ventricular
contraction
systolic pressure (SP)
(sis-TAHL-ik) maximum
arterial blood pressure during cardiac cycle
T
target cell
cell infl uenced by a certain hormone
taste bud
sense organ that contains
chemoreceptors for taste
T cell
lymphocyte derived from precursor that
differentiated in thymus;
see also
cytotoxic T
cell, helper T cell
tectorial membrane
(tek-TOR-ee-al) structure
in organ of Corti in contact with receptor cell
hairs
temporal lobe
region of cerebral cortex where
primary auditory cortex and Wernicke’s
speech center are located
temporal summation
membrane potential
produced as two or more inputs, occurring at
different times, are added together; potential
change is greater than that caused by single input
tendon
(TEN-don) collagen fi ber bundle that
connects skeletal muscle to bone and transmits
muscle contraction force to the bone
tension
force;
see also
muscle tension
tensor tympani
skeletal muscle that attaches
to the ear drum and protects the auditory
apparatus from loud sounds by dampening
the movement of the tympanum
tertiary protein structure
the three-dimensional
folded structure of a protein formed by
hydrogen bonds, hydrophobic attractions,
electrostatic interactions, and cysteine
cross-bridges
testis
(TES-tiss) (pl. testes) gonad in male
testosterone
(test-TOS-ter-own) steroid
hormone produced in interstitial cells of
testes; major male sex hormone
tetanus
(TET-ah-nus) maintained mechanical
response of muscle to high-frequency
stimulation; also the disease lockjaw
thalamus
(THAL-ah-mus) subdivision of
diencephalon; integrating center for sensory
input on its way to cerebral cortex; also
contains motor nuclei
theca
(THEE-kah) cell layer that surrounds
ovarian-follicle granulosa cells
thermogenesis
(ther-moh-JEN-ih-sis) heat
generation
thermoneutral zone
temperature range over
which changes in skin blood fl ow can regulate
body temperature
thermoreceptor
sensory receptor for
temperature and temperature changes,
particularly in low (cold receptor) or high
(warm receptor) range
theta rhythm
slow-frequency, high-amplitude
waves of the EEG associated with early stages
of slow-wave sleep
thick fi
lament
myosin fi lament in muscle cell
thin fi
lament
actin fi lament in muscle cell
thoracic cavity
(thor-ASS-ik) chest cavity
thoracic wall
chest wall
thorax
(THOR-aks) closed body cavity between
neck and diaphragm; contains lung, heart,
thymus, large vessels, and esophagus; also
called the chest
threshold potential
(THRESH-old) membrane
potential above which an excitable cell fi
res
an action potential
threshold stimulus
stimulus capable of
depolarizing membrane just to threshold
thrifty gene
gene postulated to have evolved in
order to increase the body’s ability to store
fat
thrombin
(THROM-bin) enzyme that catalyzes
conversion of fi brinogen to fi brin; has
multiple other actions in blood clotting
thrombolytic system
see
fi brinolytic system
thrombomodulin
an endothelial receptor
to which thrombin can bind, thereby
eliminating thrombin’s clot-producing effects
and causing it to bind and activate protein C
thrombosis
(throm-BOH-sis) clot formation in
body
thromboxane
an eicosanoid derived
from arachidonic acid by the action of
cyclooxygenase; among other functions,
thromboxanes are involved in platelet
aggregation
thrombus
(THROM-bus) blood clot
thymine (T)
(THIGH-meen) pyrimidine base
in DNA but not RNA
thymopoietin
(thigh-moh-POY-uh-tin) thymus-
derived hormone that regulates lymphocyte
development
thymus
(THIGH-mus) lymphoid organ in
upper part of chest; site of T-lymphocyte
differentiation
thyroglobulin
(thigh-roh-GLOB-you-lin) large
protein precursor of thyroid hormones in
colloid of follicles in thyroid gland; storage
form of thyroid hormones
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