740
Glossary
sarcoplasmic reticulum
(sar-koh-PLAZ-mik
reh-TIK-you-lum) endoplasmic reticulum
in muscle fi ber; site of storage and release of
calcium ions
satellite cell
undifferentiated cell found within
skeletal muscle tissue that can fuse and develop
into new muscle fi ber following muscle injury
satiety signal
(sah-TY-ih-tee) input to food
control centers that causes hunger to cease and
sets time period before hunger returns
saturated fatty acid
fatty acid whose carbon
atoms are all linked by single covalent bonds
saturation
occupation of all available binding sites
by their ligand
scala tympani
(SCALE-ah TIM-pah-nee) fl uid-
fi lled inner-ear compartment that receives
sound waves from basilar membrane and
transmits them to round window
scala vestibuli
(ves-TIB-you-lee) fl uid-fi lled
inner-ear compartment that receives sound
waves from oval window and transmits them to
basilar membrane and cochlear duct
Schwann cell
nonneural cell that forms myelin
sheath in peripheral nervous system
sclera
(SKLAIR-ah) the tough, outermost tissue
layer of the eyeball
scrotum
(SKROH-tum) sac that contains testes
and epididymides
secondary active transport
active transport in
which energy released during transmembrane
movement of one substance from higher
to lower concentration is transferred to the
simultaneous movement of another substance
from lower to higher concentration
secondary lymphoid organ
lymph node,
spleen, tonsil, or lymphocyte accumulation
in gastrointestinal, respiratory, urinary, or
reproductive tract; site of stimulation of
lymphocyte response
secondary oocyte
daughter cell (23
chromosomes) retaining most cytoplasm
resulting from fi rst meiotic division in the
ovary
secondary peristalsis
(per-ih-STAL-sis)
esophageal peristaltic waves not immediately
preceded by pharyngeal phase of swallow
secondary protein structure
the helical and beta-
sheet structure of a protein
secondary sexual characteristic
external
difference between male and female not
directly involved in reproduction
secondary spermatocyte
a 23-chromosome cell
resulting from the fi rst meiotic division of the
primary spermatocyte in the testes
second messenger
intracellular substance that
serves as relay from plasma membrane to
intracellular biochemical machinery, where it
alters some aspect of cell’s function
secretin
(SEEK-reh-tin) peptide hormone secreted
by upper small intestine; stimulates pancreas to
secrete bicarbonate into small intestine
secretion
(sih-KREE-shun) elaboration and
release of organic molecules, ions, and water by
cells in response to specifi c stimuli
secretory phase
(SEEK-rih-tor-ee) stage of
menstrual cycle following ovulation during
which secretory type of endometrium develops
secretory vesicle
membrane-bound vesicle
produced by Golgi apparatus; contains protein
to be secreted by cell
segmentation
(seg-men-TAY-shun) series
of stationary rhythmical contractions and
relaxations of rings of intestinal smooth muscle;
mixes intestinal contents
selective attention
paying attention to or
focusing on a particular stimulus or event
while ignoring other ongoing sources of
information
semen
(SEE-men) sperm-containing fl uid of male
ejaculate
semicircular canal
passage in temporal bone;
contains sense organs for equilibrium and
movement
seminal vesicle
one of pair of exocrine glands in
males that secrete fl uid into vas deferens
seminiferous tubule
(sem-ih-NIF-er-ous) tubule
in testis in which sperm production occurs;
lined with Sertoli cells
semipermeable membrane
(sem-ee-PER-me-ah-
bul) membrane permeable to some substances
(usually water) but not to others (some
solutes)
sensation
the mental perception of a stimulus
sensorimotor cortex
(sen-sor-ee-MOH-tor)
all areas of cerebral cortex that play a role in
skeletal muscle control
sensory information
information that originates
in stimulated sensory receptors
sensory pathway
a group of neuron chains, each
chain consisting of three or more neurons
connected end-to-end by synapses; carries
action potentials to those parts of the brain
involved in conscious recognition of sensory
information
sensory receptor
a cell or portion of a cell that
contains structures or chemical molecules
sensitive to changes in an energy form in
the outside world or internal environment;
in response to activation by this energy, the
sensory receptor initiates action potentials in
that cell or an adjacent one
sensory system
part of nervous system that
receives, conducts, or processes information
that leads to perception of a stimulus
sensory transduction
neural process of changing
a sensory stimulus into a change in neuronal
function
sensory unit
afferent neuron plus receptors it
innervates
serosa
(sir-OH-sah) connective-tissue layer
surrounding outer surface of stomach and
intestines
serotonin
(sair-oh-TONE-in) biogenic amine
neurotransmitter; paracrine agent in blood
platelets and digestive tract; also called
5-hydroxytryptamine,
or
5-HT
Sertoli cell
(sir-TOH-lee) cell intimately
associated with developing germ cells in
seminiferous tubule; creates blood-testis
barrier, secretes fl uid into seminiferous tubule,
and mediates hormonal effects on tubule
Sertoli cell barrier
barrier to the movement of
chemicals from the blood into the lumen of the
seminiferous tubules in the testes
serum
(SEER-um) blood plasma from which
fi brinogen and other clotting proteins have
been removed as result of clotting
set point
steady-state value maintained by
homeostatic control system
sex chromatin
(CHROM-ah-tin) nuclear mass
not usually found in cells of males; condensed
X chromosome
sex chromosome
X or Y chromosome
sex determination
genetic basis of individual’s
sex, XY determining male, and XX, female
sex differentiation
development of male or
female reproductive organs
sex hormone
estrogen, progesterone,
testosterone, or related hormones
shaft
portion of bone between epiphyseal plates
shear stress
force exerted perpendicular to a
surface (e.g., force exerted on the walls of a
vessel by fl uid fl owing past)
shivering thermogenesis
neurally induced cycles
of contraction and relaxation of skeletal muscle
in response to decreased body temperature;
little or no external work is performed, and
thus the increased metabolism of muscle leads
primarily to heat production
short-loop negative feedback
infl uence of
hypothalamus by an anterior pituitary hormone
short refl
ex
local neural loop from gastrointestinal
receptors to nerve plexuses
short-term memory
storage of incoming neural
information for seconds to minutes; may be
converted into long-term memory
sigmoid colon
(SIG-moid)
S
-shaped terminal
portion of colon
signal sequence
initial portion of newly
synthesized protein (if protein is destined for
secretion)
signal transduction pathway
sequence of
mechanisms that relay information from
plasma-membrane receptor to cell’s response
mechanism;
see also
transduction
single-unit smooth muscle
smooth muscle
that responds to stimulation as single unit
because gap junctions join muscle fi bers,
allowing electrical activity to pass from cell
to cell
sinoatrial (SA) node
(sy-noh-AY-tree-al) region
in right atrium of heart containing specialized
cardiac muscle cells that depolarize
spontaneously faster than other cells in the
conducting system; determines heart rate
sinus
vascular channel for the passage of blood or
lymph
skeletal muscle
striated muscle attached to bone
or skin and responsible for skeletal movements
and facial expression; controlled by somatic
nervous system
skeletal muscle pump
pumping effect of
contracting skeletal muscles on blood fl ow
through underlying vessels
skeletomotor fi
ber
see
extrafusal fi ber
sleep
see
NREM sleep, REM sleep
sliding-fi
lament mechanism
process of muscle
contraction in which shortening occurs by
thick and thin fi laments sliding past each other
slow fi
ber
muscle fi ber whose myosin has low
ATPase activity
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