Glossary G-7flavoprotein (fla 0 vo-pro 9 te-in) A conjugated
protein containing a flavin pigment that is involved
in electron transport within the mitochondria.
follicle (fol 9 ̆ı-k 9 l) A microscopic hollow structure
within an organ. Follicles are the functional units of
the thyroid gland and of the ovary.
foramen ovale (f ̆o-ra 9 men o-val 9 e) An opening
normally present in the atrial septum of the fetal
heart that allows direct communication between the
right and left atria.
fovea centralis (fo 9 ve- ̆a sen-tra 9 lis) A tiny pit in
the macula lutea of the retina that contains slim,
elongated cones. It provides the highest visual acuity
(clearest vision).
Frank-Starling law of the heart The statement
describing the relationship between end- diastolic
volume and stroke volume of the heart. A greater
amount of blood in a ventricle prior to contraction
results in greater stretch of the myocardium, and by
this means produces a contraction of greater strength.
free radical A molecule that contains an atom with
an unpaired electron in an orbital that can contain a
maximum of two electrons. Free radicals are highly
reactive and function in a number of normal and
pathological processes.
FSH follicle-stimulating hormone One of
the two gonadotropic hormones secreted by the
anterior pituitary. In females, FSH stimulates the
development of the ovarian follicles; in males,
it stimulates the production of sperm in the
seminiferous tubules.G
GABA gamma-aminobutyric (gam 0 ̆a- ̆a-me 0 no-
byoo-tir 9 ik) acid An amino acid believed to function
as an inhibitory neurotransmitter in the central
nervous system.
gamete (gam 9 ̄et) Collective term for haploid germ
cells: sperm and ova.
gamma motoneuron (gam 9 ̆a mo 0 t ̆o-noor 9 on)
The type of somatic motor neuron that stimulates
intrafusal fibers within the muscle spindles.
ganglion (gang 9 gle-on) A grouping of nerve cell
bodies located outside the brain and spinal cord.
gap junctions Specialized regions of fusion
between the cell membranes of two adjacent cells that
permit the diffusion of ions and small molecules from
one cell to the next. These regions serve as electrical
synapses in certain areas, such as in cardiac muscle.
gas exchange The diffusion of oxygen and carbon
dioxide down their concentration gradients that
occurs between pulmonary capillaries and alveoli,
and between systemic capillaries and the surrounding
tissue cells.
gastric (gas 9 trik) intrinsic factor A glycoprotein
secreted by the stomach that is needed for the
absorption of vitamin B 12.
gastric juice The secretions of the gastric mucosa.
Gastric juice contains water, hydrochloric acid, and
pepsinogen as major components.
gastrin (gas 9 trin) A hormone secreted by the
stomach that stimulates the gastric secretion
of hydrochloric acid and pepsin.
gastroileal (gas 9 tro-il 0 e-al) reflex The reflex
in which increased gastric activity causes increased
motility of the ileum and increased movement of
chyme through the ileocecal sphincter.
gates A term used to describe structures within
the cell membrane that regulate the passage of
ions through membrane channels. Gates may beconsisting of varying proportions of extracellular
fluid, a gel-like ground substance, and extracellular
protein fibers, including collagen. In the hard
connective tissues of bone, enamel, and dentin, the
matrix also contains an inorganic component of
calcium phosphate.
extrafusal (eks 0 tr ̆a-fyooz 9 al) fibers The ordinary
muscle fibers within a skeletal muscle; not found
within the muscle spindles.
extraocular (eks 0 tr ̆a-ok 9 y ̆u-lar) muscles The
muscles that insert into the sclera of the eye. They
act to change the position of the eye in its orbit (as
opposed to the intraocular muscles, such as those of
the iris and ciliary body within the eye).
extrapyramidal (eks 0 tr ̆a-p ̆ı-ram 9 ̆ı-dl) motor
tracts Neural pathways that are situated outside of,
or that are “independent of,” pyramidal tracts. The
major extrapyramidal tract is the reticulospinal tract,
which originates in the reticular formation of the
brain stem and receives excitatory and inhibitory
input from both the cerebrum and the cerebellum.
The extrapyramidal tracts are thus influenced by
activity in the brain involving many synapses,
and they appear to be required for fine control of
voluntary movements.F
facilitated (f ̆a-sil 9 ̆ı-ta 0 tid) diffusion The carrier-
mediated transport of molecules through the cell
membrane along the direction of their concentration
gradients. It does not require the expenditure of
metabolic energy.
FAD flavin adenine dinucleotide (fla 9 vin
ad 9 n- ̄en di-noo 9 kle- ̄o-t ̄ıd) A coenzyme derived from
riboflavin that participates in electron transport
within the mitochondria.
FAS A surface receptor produced by T
lymphocytes during an infection. After a few days,
the activated T lymphocytes begin to produce
another surface molecule, FAS ligand. The bonding
of FAS with FAS ligand, on the same or on different
cells, triggers apoptosis of the lymphocytes.
feces (fe 9 s ̄ez) The excrement discharged from the
large intestine.
fertilization (fer 9 t ̆ı-l ̄ı-za 0 shun) The fusion of an
ovum and spermatozoon.
fiber, muscle A skeletal muscle cell.
fiber, nerve An axon of a motor neuron or the
dendrite of a pseudounipolar sensory neuron in the PNS.
fibrillation (fib 0 r ̆ı-la 9 shun) A condition of cardiac
muscle characterized electrically by random and
continuously changing patterns of electrical activity
and resulting in the inability of the myocardium to
contract as a unit and pump blood. It can be fatal if it
occurs in the ventricles.
fibrin (fi 9 brin) The insoluble protein formed from
fibrinogen by the enzymatic action of thrombin
during the process of blood clot formation.
fibrinogen (fi-brin 9 ̆o-jen) A soluble plasma protein
that serves as the precursor of fibrin; also called
factor I.
flaccid paralysis (flak 9 sid p ̆a-ral 9 ̆ı-sis) The
inability to contract muscles, resulting in a loss of
muscle tone. This may be due to damage to lower
motor neurons or to factors that block neuromuscular
transmission.
flagellum (fl ̆a-jel 9 um) A whiplike structure that
provides motility for sperm.
flare-and-wheal reaction A cutaneous reaction
to skin injury or to the administration of antigens
produced by release of histamine and related molecules;
characterized by local edema and a red flare.and lines body surfaces and forms exocrine and
endocrine glands.
EPSP excitatory postsynaptic (p ̄ost 0 s ̆ı-nap 9 tik)
potential A graded depolarization of a postsynaptic
membrane in response to stimulation by a
neurotransmitter chemical. EPSPs can be summated,
but they can be transmitted only over short distances;
they can stimulate the production of action potentials
when a threshold level of depolarization is attained.
equilibrium (e 0 kw ̆ı-lib 9 re-um) potential The
hypothetical membrane potential that would be
created if only one ion were able to diffuse across
a membrane and reach a stable, or equilibrium,
state. In this stable state, the concentrations of the
ion would remain constant inside and outside the
membrane, and the membrane potential would be
equal to a particular value.
erythroblastosis fetalis ( ̆e-rith 0 ro-blas-to 9 sis
fe-tal 9 is) Hemolytic anemia in an Rh-positive
newborn caused by maternal antibodies against the
Rh factor that have crossed the placenta.
erythrocyte ( ̆e-rith 9 r ̆o-s ̄ıt) A red blood cell.
Erythrocytes are the formed elements of blood that
contain hemoglobin and transport oxygen.
erythropoietin ( ̆e-rith 0 ro-poi 9 ̆e-tin) A hormone
secreted by the kidneys that stimulates the bone
marrow to produce red blood cells.
essential amino acids The eight amino acids in
adults or nine amino acids in children that cannot be
made by the human body; therefore, they must be
obtained in the diet.
estradiol (es 0 tr ̆a-di 9 ol) The major estrogen (female
sex steroid hormone) secreted by the ovaries.
estrus (es 9 trus) cycle Cyclic changes in the
structure and function of the ovaries and female
reproductive tract, accompanied by periods of “heat”
(estrus), or sexual receptivity; the lower mammalian
equivalent of the menstrual cycle, but differing from
the menstrual cycle in that the endometrium is not
shed with accompanying bleeding.
excitation-contraction coupling The means
by which electrical excitation of a muscle
results in muscle contraction. This coupling is
achieved by Ca^21 , which enters the muscle cell
cytoplasm in response to electrical excitation
and which stimulates the events culminating in
contraction.
exergonic (ek 0 ser-gon 9 ik) Denoting chemical
reactions that liberate energy.
exocrine (ek 9 s ̆o-krin) gland A gland that
discharges its secretion through a duct to the outside
of an epithelial membrane.
exocytosis (ek 0 so-si-to 9 sis) The process of
cellular secretion in which the secretory products
are contained within a membrane-enclosed vesicle.
The vesicle fuses with the cell membrane so that
the lumen of the vesicle is open to the extra cellular
environment.
exon (ek 9 son) A nucleotide sequence in DNA that
codes for the production of messenger RNA.
exteroceptor (ek 0 ster-o-cep 9 tor) A sensory
receptor that is sensitive to changes in the external
environment (as opposed to an interoceptor).
extracellular (eks-tra-sel 9 u-lar) compartment
All of the material outside of cells, including the
extracellular fluid with all of its solutes, insoluble
protein fibers, and, in some cases, crystals. Also
called the extracellular matrix.
extracellular fluid The fluid outside of cells,
including the blood plasma and the interstitial fluid
within the tissues.
extracellular matrix (eks-tra-sel 9 u-lar ma 9 triks)
The extracellular material of connective tissue,fox36375_glo_G1-G19.indd 7fox36375_glo_G1-G19.indd 7 2/4/15 12:29 PM2/4/15 12:29 PM