Glossary
727
foot process
large extension of sarcoplasmic
reticulum calcium channels (ryanodine
receptors), which connect them to the
T-tubule membrane and mediate excitation-
contraction coupling in skeletal muscle; also
known as
junctional feet
forebrain
large, anterior brain subdivision
consisting of right and left cerebral
hemispheres (the cerebrum) and diencephalon
formed element
solid phase of blood, including
cells (erythrocytes and leukocytes) and cell
fragments (platelets)
fovea centralis
(FOH-vee-ah) area near center
of retina where cones are most concentrated;
gives rise to most acute vision
Frank-Starling mechanism
the relationship
between stroke volume and end-diastolic
volume such that stroke volume increases as
end-diastolic volume increases; also called
Starling’s law of the heart
fraternal twins
dizygotic twins that occur when
two eggs are fertilized
free radical
atom that has an unpaired electron in
its outermost orbital; molecule containing such
an atom
free-running rhythm
cyclical activity driven by
biological clock in absence of environmental cues
frequency
number of times an event occurs per
unit time
frontal lobe
region of anterior cerebral cortex
where motor areas, Broca’s speech center, and
some association cortex are located
fructose
(FRUK-tose) fi ve-carbon sugar; present
in sucrose (table sugar)
F-type sodium channel
the “funny” sodium-
conducting channel mainly responsible for the
inward fl ow of positive current in autorhythmic
cardiac cells
functional residual capacity
lung volume after
relaxed expiration
functional site
binding site on allosteric protein
that, when activated, carries out protein’s
physiological function; also called active site
fundus
upper portion of the stomach; secretes
mucus, pepsinogen, and hydrochloric acid
fused tetanus
(TET-ah-nuss) skeletal muscle
activation in which action potential frequency
is suffi ciently high to cause a smooth,
sustained, maximal strength contraction
fused-vesicle channel
endocytotic or exocytotic
vesicles that have fused to form a continuous
water-fi lled channel through capillary
endothelial cell
G
GABA (gamma-aminobutyric acid)
an amino
acid neurotransmitter commonly occurring
at inhibitory synapses in the central nervous
system
gallbladder
small sac under the liver; concentrates
bile and stores it between meals; contraction of
gallbladder ejects bile, which eventually fl ows
into small intestine
gamete
(GAM-eet) germ cell or reproductive cell;
sperm in male and egg in female
gametogenesis
(gah-mee-toh-JEN-ih-sis) gamete
production
gamma globulin
immunoglobulin G (IgG), most
abundant class of plasma antibodies
gamma motor neuron
small motor neuron that
controls intrafusal muscle fi bers in muscle
spindles
ganglion
(GANG-glee-on) (pl. ganglia) generally
reserved for cluster of neuron cell bodies
outside CNS
ganglion cell
retinal neuron that is postsynaptic
to bipolar cells; axons of ganglion cells form
optic nerve
gap junction
protein channels linking cytosol
of adjacent cells; allows ions and small
molecules to fl ow between cytosols of the
connected cells
gastric
(GAS-trik) pertaining to the stomach
gastric phase
(of gastrointestinal control)
initiation of neural and hormonal
gastrointestinal refl exes by stimulation of
stomach wall
gastrin
(GAS-trin) peptide hormone secreted by
antral region of stomach; stimulates gastric acid
secretion
gastroileal refl
ex
(gas-troh-IL-ee-al) increase in
contractions of ileum during gastric emptying
gastrointestinal (GI) system
(gas-troh-in-TES-
tin-al) gastrointestinal tract plus salivary glands,
liver, gallbladder, and pancreas
gastrointestinal tract
mouth, pharynx, esophagus,
stomach, and small and large intestines
gating
opening or closing ion channels
gene
unit of hereditary information; portion of
DNA containing information required to
determine a protein’s amino acid sequence
gene cloning
process of forming identical DNA
sequences using genetic engineering techniques
genetic code
three-nucleotide sequence in a gene;
indicates the location of a particular amino acid
in the protein specifi ed by that gene
genome
complete set of an organism’s genes
genotype
the set of alleles present in an
individual; determines genetic sex (XX, female;
XY, male)
germ cell
cell that gives rise to male or female
gametes (sperm and eggs)
gestation
(jess-TAY-shun) length of time of
intrauterine fetal development (usually about
nine months in humans)
ghrelin
(GREH-lin) hormone released from cells
of the stomach; stimulates hunger
gland
see
endocrine gland, exocrine gland
glial cell
(GLEE-al) nonneuronal cell in CNS;
helps regulate extracellular environment of
CNS; also called
neuroglia
globin
(GLOH-bin) collective term for the four
polypeptide chains of the hemoglobin molecule
globulin
(GLOB-you-lin) one of a family of
proteins found in blood plasma
glomerular capillary
very small blood vessel
within the glomerulus of the kidney through
which plasma is fi ltered
glomerular fi
ltrate
ultrafi ltrate of plasma
produced in the glomerulus that is usually free
of cells and large proteins
glomerular fi
ltration
process by which
components of plasma in the glomerular
capillary are passed to the Bowman’s space of
the glomerulus—process is governed by net
glomerular fi ltration pressure
glomerular fi
ltration rate (GFR)
volume of
fl uid fi ltered from renal glomerular capillaries
into Bowman’s capsule per unit time
glomerulus
(gloh-MER-you-lus) tufts of glomerular
capillaries at beginning of kidney nephron
glottis
opening between vocal cords through
which air passes, and surrounding area
glucagon
(GLOO-kah-gahn) peptide hormone
secreted by alpha cells of pancreatic islets of
Langerhans; leads to rise in plasma glucose
glucocorticoid
(gloo-koh-KOR-tih-koid) steroid
hormone produced by adrenal cortex and
having major effects on nutrient metabolism
gluconeogenesis
(gloo-koh-nee-oh-JEN-ih-sis)
formation of glucose by the liver or kidneys
from pyruvate, lactate, glycerol, or amino acids
glucose
major monosaccharide in the body; a six-
carbon sugar, C
6
H
12
O
6
; also called blood sugar
glucose-counterregulatory control
neural or
hormonal factors that oppose insulin’s actions;
glucagon, epinephrine, sympathetic nerves to
liver and adipose tissue, cortisol, and growth
hormone
glucose-dependent insulinotropic peptide
(GIP)
intestinal hormone; stimulates insulin
secretion in response to glucose and fat in
small intestine
glucose-6-phosphate
(FOS-fate) fi rst
intermediate in glycolytic pathway
glucose sparing
switch from glucose to fat
utilization by most cells during postabsorptive
state
glutamate
(GLU-tah-mate) anion formed
from the amino acid glutamic acid; a major
excitatory CNS neurotransmitter
glutamine
(GLOO-tah-meen) glutamate having
an extra NH
3
gluten
wheat protein
glycerol
(GLISS-er-ol) three-carbon carbohydrate;
forms backbone of triglyceride
glycine
(GLY-seen) an amino acid; a
neurotransmitter at some inhibitory synapses
in CNS
glycocalyx
(gly-koh-KAY-lix) fuzzy coating on
extracellular surface of plasma membrane;
consists of short, branched carbohydrate chains
glycogen
(GLY-koh-jen) highly branched
polysaccharide composed of glucose subunits;
major carbohydrate storage form in body
glycogenolysis
(gly-koh-jen-NOL-ih-sis)
glycogen breakdown to glucose
glycogen phosphorylase
intracellular enzyme
required to begin the process of breaking down
glycogen into glucose; inhibited by insulin
glycogen synthase
intracellular enzyme required
to synthesize glycogen; stimulated by insulin
glycolysis
(gly-KOL-ih-sis) metabolic pathway
that breaks down glucose to two molecules
of pyruvate (aerobically) or two molecules of
lactate (anaerobically)
glycolytic fi
ber
skeletal muscle fi ber that has a
high concentration of glycolytic enzymes and
large glycogen stores; white muscle fi ber
glycoprotein
protein containing covalently linked
carbohydrates
Goldman-Hodgkin-Katz (GHK) equation
calculation for electrochemical equilibrium
when a membrane is permeable to more than
one ion
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