Glossary
741
slowly adapting receptor
sensory receptor that
fi res repeatedly as long as a stimulus is ongoing
slow-oxidative fi
ber
type of skeletal muscle fi ber
that has slow intrinsic contraction speed but
fatigues very slowly due to abundant capacity
for production of ATP by aerobic oxidative
phosphorylation
slow wave
slow, rhythmic oscillation of smooth-
muscle membrane potentials toward and away
from threshold, due to regular fl uctuations in
ionic permeability
slow-wave sleep
see
NREM sleep
small intestine
longest portion of the
gastrointestinal tract; between the stomach and
large intestine
smooth endoplasmic reticulum
see
endoplasmic
reticulum
smooth muscle
nonstriated muscle that surrounds
hollow organs and tubes;
see also
multiunit
smooth muscle, single-unit smooth muscle
smooth muscle tone
smooth-muscle tension due
to low-level cross-bridge activity in absence of
external stimuli
SNARE protein
soluble N-ethylmaleimide-
sensitive fusion protein attachment protein
receptor
sodium inactivation
turning off of increased
sodium permeability at action potential peak
soft palate
(PAL-et) nonbony region at back of
roof of mouth
solute
(SOL-yoot) substances dissolved in a
liquid
solution
liquid (solvent) containing dissolved
substances (solutes)
solvent
liquid in which substances are dissolved
soma
cell body of neuron
somatic
(soh-MAT-ik) pertaining to the body;
related to body’s framework or outer walls,
including skin, skeletal muscle, tendons, and
joints
somatic nervous system
component of efferent
division of peripheral nervous system;
innervates skeletal muscle;
compare
autonomic
nervous system
somatic receptor
neural receptor in the
framework or outer wall of the body that
responds to mechanical stimulation of skin
or hairs and underlying tissues, rotation or
bending of joints, temperature changes, or
painful stimuli
somatic sensation
feelings/perceptions coming
from muscle, skin, and bones
somatosensory cortex
(suh-mat-uh-SEN-suh-
ree) strip of cerebral cortex in parietal lobe in
which nerve fi bers transmitting somatic sensory
information synapse
somatostatin (SS)
(suh-mat-uh-STAT-in)
hypophysiotropic hormone that inhibits
growth hormone secretion by anterior
pituitary; possible neurotransmitter; also found
in stomach and pancreatic islets
somatotopic map
a representation of the different
regions of the body formed by neurons of the
cerebral cortex
sound wave
air disturbance due to variations
between regions of high air molecule density
(compression) and low density (rarefaction)
spatial summation
(SPAY-shul) adding together
effects of simultaneous inputs to different
places on a neuron to produce potential change
greater than that caused by single input
specifi
c ascending pathway
chain of synaptically
connected neurons in CNS, all activated by
sensory units of same type
specifi
c immune defense
response that depends
upon recognition of specifi c foreign material
for reaction to it
specifi
city
selectivity; ability of binding site to
react with only one, or a limited number of,
types of molecules
sperm
see
spermatozoan
spermatic cord
structure including the vas
deferens and blood vessels and nerves
supplying the testes
spermatid
(SPER-mah-tid) immature sperm
spermatogenesis
(sper-mah-toh-JEN-ih-sis)
sperm formation
spermatogonium
(sper-mah-toh-GOH-nee-um)
undifferentiated germ cell that gives rise to
primary spermatocyte
spermatozoan
(spur-ma-toh-ZOH-in) male
gamete; also called sperm
sperm capacitation
(kah-pas-ih-TAY-shun)
process by which sperm in female reproductive
tract gains ability to fertilize egg
sphincter
(SFINK-ter) smooth-muscle ring that
surrounds a tube, closing tube as muscle
contracts
sphincter of Oddi
(OH-dye) smooth-muscle ring
surrounding common bile duct at its entrance
into duodenum
sphygmomanometer
(sfi g-moh-mah-NOM-eh-ter)
device consisting of infl atable cuff and pressure
gauge for measuring arterial blood pressure
spinal nerve
one of 86 peripheral nerves (43 pairs)
that join spinal cord
spinal refl
ex
refl ex whose afferent and efferent
components are in spinal nerves; can occur in
absence of brain control
spleen
largest lymphoid organ; located between
stomach and diaphragm
spliceosome
protein and nuclear RNA complex
that removes introns and links exons together
during gene transcription
SRY
gene
gene on the Y chromosome that
determines development of testes in genetic
male
stable balance
net loss of substance from body
equals net gain, and amount of substance in
body neither increases nor decreases;
compare
negative balance, positive balance
stapedius
(stah-PEE-dee-us) skeletal muscle
that attaches to the stapes and protects
the auditory apparatus by dampening
the movement of the ear ossicles during
persistent, loud sounds
stapes
one of three bones in the inner ear
that transmit movements of the tympanic
membrane to the inner ear
starch
moderately branched plant polysaccharide
composed of glucose subunits
Starling force
factor that determines direction
and magnitude of fl uid movement across
capillary wall
Starling’s law of the heart
see
Frank-Starling
mechanism
state of consciousness
degree of mental alertness—
that is, whether awake, drowsy, asleep, and so on
steady state
no net change; continual energy
input to system is required, however, to
prevent net change;
compare
equilibrium
stem cell
cell that in adult body divides
continuously and forms supply of cells for
differentiation
stereocilia
(ster-ee-oh-SIL-ee-ah) nonmotile cilia
containing actin fi laments
steroid
(STER-oid) lipid subclass; molecule
consists of four interconnected carbon rings to
which polar groups may be attached
steroid hormone
any of a family of hormones,
like progesterone, whose structure is derived
from cholesterol
steroid hormone receptor superfamily
class of
intracellular receptor proteins that bind steroid
hormones and other lipophilic molecules and
induce changes in gene transcription
stimulus
detectable change in internal or external
environment
stomach
expandable, saclike structure in the
gastrointestinal tract between the esophagus
and small intestine; site of initial digestion of
proteins
“stop”signal
three-nucleotide sequence in
mRNA that signifi es end of protein coding
sequence
stress
environmental change that must be
adapted to if health and life are to be
maintained; event that elicits increased
cortisol secretion
stretch receptor
afferent nerve ending that is
depolarized by stretching;
see also
muscle-
spindle stretch receptor
stretch refl
ex
monosynaptic refl ex, mediated
by muscle-spindle stretch receptor, in which
muscle stretch causes contraction of that
muscle
striated muscle
(STRY-ay-ted) muscle having
transverse banding pattern due to repeating
sarcomere structure;
see also
cardiac muscle,
skeletal muscle
stroke volume
blood volume ejected by a
ventricle during one heartbeat
strong acid
acid that ionizes completely to form
hydrogen ions and corresponding anions when
dissolved in water;
compare
weak acid
strychnine
an alkaloid nervous system poison
that blocks the action of the inhibitory
neurotransmitter, glycine
subarachnoid space
space between the
arachnoid and pia mater meninges containing
cerebrospinal fl uid
subcortical nuclei
groups of cells in brain below
the cerebral cortex
submucosa
layer of tissue beneath the
gastrointestinal mucosa
submucosal plexus
(sub-mu-KOH-zal PLEX-us)
nerve-cell network in submucosa of esophageal,
stomach, and intestinal walls
substance P
neuropeptide neurotransmitter
released by afferent neurons in pain pathway as
well as other sites
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