G-12
Glossary
Insulin
A hormone that enhances the carrier-mediated diffusion of glu-
cose into tissue cells, thus lowering blood glucose levels.
Insulin resistance
State in which a greater than normal amount of insu-
lin is required to maintain normal glucose blood levels.
Integration
Te process by which the nervous system processes and
interprets sensory input and makes decisions about what should be done
at each moment.
Integumentary system
(in-teg
0
u-men
9
tar-e) Skin and its derivatives;
provides the external protective covering of the body.
Intercalated discs
(in-ter
9
kah-la
0
ted) Specialized connections between
myocardial cells containing gap junctions and desmosomes.
Interferons (IFNs)
(in-ter-fēr
9
ons) Proteins released from virus-infected
(and other) cells that protect uninfected cells from viral takeover. Also
inhibit some cancers.
Internal capsule
Band of projection fibers that runs between the basal
nuclei and the thalamus.
Internal respiration
Exchange of gases between blood and tissue fluid
and between tissue fluid and cells.
Interneuron (association neuron)
Nerve cell located between motor
and sensory neurons that shuttles signals through CNS pathways where
integration occurs.
Interoceptor
(in
0
ter-o-sep
9
tor) Sensory receptor in the viscera that is
sensitive to changes and stimuli within the body’s internal environment;
also called visceroceptor.
Interphase
One of two major periods in the cell life cycle; includes the
period from cell formation to cell division.
Interstitial endocrine cells
Cells located in the loose connective tissue sur-
rounding the seminiferous tubules; they produce androgens (most impor-
tantly testosterone), which are secreted into the surrounding interstitial fluid.
Interstitial fluid (IF)
(in
0
ter-stish
9
al) Fluid between the cells.
Interstitial lamellae
Incomplete lamellae that lie between intact osteons,
filling the gaps between forming osteons, or representing the remnants of
an osteon that has been cut through by bone remodeling.
Intervertebral discs
(in
0
ter-ver
9
teh-brul) Discs of fibrocartilage between
vertebrae.
Intracapsular ligament
Ligament located within and separate from the
articular capsule of a synovial joint.
Intracellular fluid (ICF)
(in
0
trah-sel
9
u-ler) Fluid within a cell.
Intrinsic factor
Substance produced by the stomach that is required for
vitamin B
12
absorption.
Intron
Noncoding segment or portion of DNA that ranges from 60 to
100,000 nucleotides long.
Involuntary muscle
Muscle that cannot ordinarily be controlled volun-
tarily (e.g., smooth and cardiac muscle).
Involuntary nervous system
Te autonomic nervous system.
Ion
9
on) Atom or molecule with a positive or negative electric charge.
Ionic bond
(ī-ah
9
nik) Chemical bond formed by electron transfer be-
tween atoms.
Ipsilateral
(ip
0
sih-lă
9
ter-ul) Situated on the same side.
Ischemia
(is-ke
9
me-ah) Local decrease in blood supply.
Isogra±
±issue gra² donated by an identical twin.
Isomer
(i
9
so-mer) One of two or more substances that has the same mo-
lecular formula but with its atoms arranged differently.
Isometric contraction
(i
0
so-mĕ
9
trik) Contraction in which the muscle
does not shorten (the load is too heavy) but its internal tension increases.
Hypotonic
(hi
0
po-ton
9
ik) Below normal tone or tension.
Hypotonic solution
A solution that is more dilute (containing fewer
nonpenetrating solutes) than the reference cell. Cells placed in hypotonic
solutions plump up rapidly as water rushes into them.
Hypoventilation
A decrease in the depth and rate of breathing; charac-
terized by an increase in blood carbon dioxide.
Hypovolemic shock
(hi
0
po-vo-le
9
mik) Most common form of shock;
results from extreme blood loss.
Hypoxia
(hi-pok
9
se-ah) Condition in which inadequate oxygen is avail-
able to tissues.
Ileocecal valve
(il
0
e-o-se
9
kal) Site where the small intestine joins the
large intestine.
Ileum
(il
9
e-um) ±erminal part of the small intestine; between the jeju-
num and the cecum of the large intestine.
Immune system
A functional system whose components attack foreign
substances or prevent their entry into the body.
Immunity
(im
0
ūn
9
ĭ-te) Ability of the body to resist many agents (both
living and nonliving) that can cause disease; resistance to disease.
Immunocompetence
Ability of the body’s immune cells to recognize
(by binding) specific antigens; reflects the presence of plasma
membrane–bound receptors.
Immunodeficiency
Any congenital or acquired condition causing a
deficiency in the production or function of immune cells or certain mol-
ecules (complement, antibodies, etc.) required for normal immunity.
In vitro
(in ve
9
tro) In a test tube, glass, or artificial environment.
In vivo
(in ve
9
vo) In the living body.
Incompetent valve
Valve which does not close properly.
Incontinence
Inability to control micturition or defecation voluntarily.
Infarct
(in
9
farkt) Region of dead, deteriorating tissue resulting from a
lack of blood supply.
Infectious mononucleosis
Highly contagious viral disease; marked by
excessive agranulocytes.
Inferior (caudal)
Pertaining to a position toward the lower or tail end of
the long axis of the body.
Inferior vena cava
Vein that returns blood from body areas below the
diaphragm.
Inflammation
(in
0
flah-ma
9
shun) An innate (nonspecific) defensive re-
sponse of the body to tissue injury; includes dilation of blood vessels and
an increase in vessel permeability; indicated by redness, heat, swelling,
and pain.
Infundibulum
(in
0
fun-dib
9
u-lum) (1) A stalk of tissue that connects the
pituitary gland to the hypothalamus; (2) the distal end of the uterine (fal-
lopian) tube.
Inguinal
(ing
9
wĭ-nal) Pertaining to the groin region.
Inhibitory postsynaptic potential (IPSP)
A graded potential in a
postsynaptic neuron that inhibits action potential generation; usually
hyperpolarizing.
Inner cell mass
Accumulation of cells in the blastocyst from which the
embryo develops.
Innervation
(in
0
er-va
9
shun) Supply of nerves to a body part.
Inorganic compound
Chemical substances that do not contain carbon,
including water, salts, and many acids and bases.
Insertion
Movable attachment of a muscle.
Insula
Lobe of the cerebral cortex that is buried in the lateral sulcus be-
neath portions of the parietal, frontal, and temporal lobes.
previous page 1188 Human Anatomy and Physiology (9th ed ) 2012 read online next page 1190 Human Anatomy and Physiology (9th ed ) 2012 read online Home Toggle text on/off