Glossary
729
hydrogen peroxide
H
2
O
2
; chemical produced
by phagosome and highly destructive to
macromolecules
hydrolysis
(hy-DRAHL-ih-sis) breaking of
chemical bond with addition of elements
of water (—H and —OH) to the products
formed; also called hydrolytic reaction
hydrophilic
(hy-droh-FIL-ik) attracted to, and
easily dissolved in, water
hydrophobic
(hy-droh-FOH-bik) not attracted
to, and insoluble in, water
hydrostatic pressure
(hy-droh-STAT-ik) pressure
exerted by fl uid
hydroxyapatite
crystals composed primarily of
calcium and phosphate deposited in bone
matrix (mineralization)
hydroxyl group
(hy-DROX-il) —OH
hydroxyl radical
a highly reactive oxygen
derivative (free radical) that can be
formed in small amounts during oxidative
phosphorylation
hymen
membrane that partially covers the opening
to the vagina
hyper-
increased
hypercalcemia
increased plasma calcium
hypercapnea
increased arterial P
CO
2
hyperemia
(hy-per-EE-me-ah) increased blood
fl ow;
see also
active hyperemia
hyperosmotic
(hy-per-oz-MAH-tik) having total
solute concentration greater than normal
extracellular fl uid
hyperpolarize
to change membrane potential so
cell interior becomes more negative than its
resting state
hypertension
chronically increased arterial blood
pressure
hyperthermia
increased body temperature above
the set point
hypertonic
(hy-per-TAH-nik) solutions
containing a higher concentration of effectively
membrane-impermeable solute particles than
normal (isotonic) extracellular fl uid
hypertrophy
(hy-PER-troh-fee) enlargement of a
tissue or organ due to increased cell size rather
than increased cell number
hyperventilation
increased ventilation adequate
to reduce arterial P
CO
2
hypo-
too little; below
hypocalcemia
the condition of low blood (and
interstitial) calcium concentration
hypoglycemia
(hy-poh-gly-SEE-me-ah) low
blood glucose (sugar) concentration
hypoosmotic
(hy-poh-oz-MAH-tik) having total
solute concentration less than that of normal
extracellular fl uid
hypophysiotropic hormone
(hy-poh-fi z-ee-
oh-TROH-pik) any hormone secreted by
hypothalamus that controls secretion of an
anterior pituitary hormone
hypotension
low blood pressure
hypothalamic releasing hormone
(hy-poh-thah-
LAM-ik)
see
hypophysiotropic hormone
hypothalamo-pituitary portal vessels
small
veins that link the capillaries of the median
eminence at the base of the hypothalamus
to capillaries that bathe the cells of the
anterior pituitary gland; neurohormones are
secreted from the hypothalamus into these
vessels
hypothalamus
(hy-poh-THAL-ah-mus) brain
region below thalamus; responsible for
integration of many basic neural, endocrine, and
behavioral functions, especially those concerned
with regulation of internal environment
hypotonic
(hy-poh-TAH-nik) solutions
containing a lower concentration of effectively
nonpenetrating solute particles than normal
(isotonic) extracellular fl uid
hypoventilation
decrease in ventilation that
causes an increase in arterial P
CO
2
hypoxemia
low levels of oxygen in the blood
hypoxia
low levels of oxygen in the air, blood, or
tissues
H zone
one of transverse bands making up
striated pattern of cardiac and skeletal muscle;
light region that bisects A band
I
I band
one of transverse bands making up
repeating striations of cardiac and skeletal
muscle; located between A bands of adjacent
sarcomeres and bisected by Z line
IgA
class of antibodies secreted by, and acting
locally in, lining of gastrointestinal, respiratory,
and genitourinary tracts
IgD
class of antibodies whose function is
unknown
IgE
class of antibodies that mediate immediate
hypersensitivity and resistance to parasites
IgG
gamma globulin; most abundant class of
antibodies
IgM
class of antibodies that, along with IgG,
provide major specifi c humoral immunity
against bacteria and viruses
ileocecal sphincter
(il-ee-oh-SEE-kal) ring of
smooth muscle separating small and large
intestines (that is, ileum and cecum)
ileum
(IL-ee-um) fi nal, longest segment of small
intestine
immune defense
see
nonspecifi c immune defense,
specifi c immune defense
immune surveillance
(sir-VAY-lence) recognition
and destruction of cancer cells that arise in
body
immune system
widely dispersed cells and tissues
that participate in the elimination of foreign
cells, microbes, and toxins from the body
immune tolerance
the lack of immune responses
to self components
immunity
physiological mechanisms that allow
body to recognize materials as foreign or
abnormal and to neutralize or eliminate them;
see also
active immunity, passive immunity
immunoglobulin (Ig)
(im-mun-o-GLOB-you-
lin) proteins that are antibodies and antibody-
like receptors on B cells (fi ve classes are IgG,
IgA, IgD, IgM, and IgE)
immunology
the study of the defenses by which
the body destroys or neutralizes foreign cells,
microbes, and toxins
implantation
(im-plan-TAY-shun) event during
which fertilized egg becomes embedded in
uterine wall
inactivation gate
portion of the voltage-gated
sodium or potassium channel that closes the
channel
incus
one of three bones in the inner ear
that transmit movements of the tympanic
membrane to the inner ear
inferior vena cava
(VEE-nah KAY-vah) large vein
that carries blood from lower half of body to
right atrium of heart
infl
ammation
(in-fl ah-MAY-shun) local response
to injury or infection characterized by swelling,
pain, heat, and redness
infundibulum
(in-fun-DIBB-yoo-lum) the stalk
connecting the median eminence at the base of
the hypothalamus with the pituitary gland
inhibin
(in-HIB-in) protein hormone secreted by
seminiferous-tubule Sertoli cells and ovarian
granulosa cells; inhibits FSH secretion
inhibitory postsynaptic potential (IPSP)
hyperpolarizing graded potential that arises in
postsynaptic neuron in response to activation
of inhibitory synaptic endings upon it
inhibitory synapse
(SIN-apse) synapse that,
when activated, decreases likelihood that
postsynaptic neuron will fi re an action potential
(or decreases frequency of existing action
potentials)
initial segment
fi rst portion of axon plus the part
of the cell body where axon arises
initiation factor
a protein required for ribosomal
assembly and the establishment of an initiation
complex that allows new protein synthesis to
begin
inner cell mass
portion of the blastocyst that
becomes the embryo
inner ear
cochlea; contains organ of Corti
inner emotion
emotional feelings that are entirely
within a person
inner segment
portion of photoreceptor that
contains cell organelles; synapses with bipolar
cells of retina
innervate
to supply with nerves
inorganic
pertaining to substances that do not
contain carbon;
compare
organic
inorganic phosphate (P
i
)
(FOS-fate) H
2
PO
4
,
HPO
4
2–
, or PO
4
3–
inositol trisphosphate (IP
3
)
(in-OS-ih-tol-tris-
FOS-fate) second messenger that causes release
of calcium from endoplasmic reticulum into
cytosol
insensible water loss
water loss of which a person
is unaware—that is, loss by evaporation from
skin (excluding sweat) and respiratory passage
lining
inspiration
air movement from atmosphere into
lungs
inspiratory reserve volume (IRV)
maximal air
volume that can be inspired above resting tidal
volume
insulin
(IN-suh-lin) peptide hormone secreted
by beta cells of pancreatic islets of Langerhans;
has metabolic and growth-promoting effects;
stimulates glucose and amino acid uptake by
most cells and stimulates protein, fat, and
glycogen synthesis
insulin-like growth factor I (IGF-I)
insulin-like
growth factor that mediates mitosis-stimulating
effect of growth hormone on bone and other
tissues and has feedback effect on pituitary
insulin-like growth factor II
mitogenic
hormone active during fetal life; postnatal role,
if any, is unknown
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