G-10 Glossarykilocalorie (kil 9 ̆o-kal 0 ̆o-re) A unit of measurement
equal to 1,000 calories, which are units of heat.
(A kilocalorie is the amount of heat required to
raise the temperature of 1 kilogram of water 1 8 C.)
In nutrition, the kilocalorie is called a big calorie
(Calorie).
kinase (ki 9 n ̄as) Any of a class of enzymes that
transfer phosphate groups to organic molecules.
The activity of particular protein kinases may
be promoted by hormones and other regulatory
molecules. These enzymes can, in turn,
phosphorylate other enzymes and thereby regulate
their activities.
kisspeptins (kis-pep 9 tinz) A family of polypeptide
neurotransmitters released in the hypothalamus
that help to regulate the neurons that produce
gonadotropin-releasing hormone (GnRH), thus helping
to regulate many aspects of the reproductive system.
Klinefelter’s (kl ̄ın 9 fel-terz) syndrome The
syndrome produced in a male by the presence of an
extra X chromosome (genotype XXY).
knockout mice Strains of mice in which a specific
targeted gene has been inactivated by developing
the mice from embryos injected with specifically
mutated cells.
Krebs (krebz) cycle A cyclic metabolic pathway
in the matrix of mitochondria by which the acetic
acid part of acetyl CoA is oxidized and substrates
provided for reactions that are coupled to the
formation of ATP.
Kupffer (koop 9 fer) cells Phagocytic cells lining
the sinusoids of the liver that are part of the
reticuloendothelial system.L
lactate threshold A measurement of the intensity
of exercise. It is the percentage of a person’s
maximal oxygen uptake at which a rise in blood
lactate levels occurs. The average lactate threshold
occurs when exercise is performed at 50% to 70% of
the maximal oxygen uptake (aerobic capacity).
lactose (lak 9 t ̄os) Milk sugar; a disaccharide of
glucose and galactose.
lactose intolerance The inability of many adults to
digest lactose because of a deficiency of the enzyme
lactase.
Laplace, law of The statement that the pressure
within an alveolus is directly proportional to its
surface tension and inversely proportional to its radius.
larynx (lar 9 ingks) A structure consisting of
epithelial tissue, muscle, and cartilage that serves as
a sphincter guarding the entrance of the trachea. It is
the organ responsible for voice production.
lateral inhibition The sharpening of perception
that occurs in the neural processing of sensory input.
Input from those receptors that are most greatly
stimulated is enhanced, while input from other
receptors is reduced. This results, for example, in
improved pitch discrimination in hearing.
leakage channels Ion channels in the plasma
membrane that are always open because they are not
gated. For example, there are leakage channels (in
addition to voltage-gated channels) for K^1 , that make
the resting membrane more permeable to K^1 than to
other ions.
leptin (lep 9 tin) A hormone secreted by adipose
tissue that acts as a satiety factor to reduce appetite.
It also increases the body’s caloric expenditure.
lesion (le 9 zhun) 1. A wounded or damaged area of
tissue. 2. An injury or wound. 3. A single infected
patch in a skin disease.in vivo (in ve 9 vo) Occuring within the body.
ion (i 9 on) An atom or a group of atoms that has a
net positive or a net negative charge because of a loss
or gain of electrons.
ionization (i 0 on-ı ̆-za 9 shun) The dissociation of a
solute to form ions.
ipsilateral (ip 0 s ̆ı-lat 9 er-al) On the same side (as
opposed to contralateral).
IPSP inhibitory postsynaptic potential
A hyperpolarization of the postsynaptic membrane
in response to a particular neurotransmitter chemical,
which makes it more difficult for the postsynaptic
cell to attain the threshold level of depolarization
required to produce action potentials. IPSPs are
responsible for post synaptic inhibition.
ischemia ( ̆ı-ske 9 me- ̆a) A rate of blood flow to an
organ that is inadequate to supply sufficient oxygen
and maintain aerobic respiration in that organ.
isoenzymes (i 0 so-en 9 zimz) Enzymes, usually
produced by different organs, that catalyze the same
reaction but that differ from each other in amino acid
composition.
isometric (i 0 s ̆o-met 9 rik) contraction Muscle
contraction in which there is no appreciable
shortening of the muscle.
isotonic (i 0 s ̆o-ton 9 ik) contraction Muscle
contraction in which the muscle shortens in length
and maintains approximately the same amount of
tension throughout the shortening process.
isotonic solution A solution having the same
total solute concentration, osmolality, and osmotic
pressure as the solution with which
it is compared; a solution with the same solute
concentration and osmotic pressure as plasma.J
jaundice (jawn 9 dis) A condition characterized by
high blood bilirubin levels and staining of the tissues
with bilirubin, which imparts a yellow color to the
skin and mucous membranes.
junctional (jungk 9 shun-al) complexes Structures
that join adjacent epithelial cells together, including
the zonula occludens, zonula adherens, and macula
adherens (desmosome).
juxtaglomerular (juk 0 st ̆a-glo-mer 9 y ̆u-lar)
apparatus A renal structure in which regions
of the nephron tubule and afferent arteriole
are in contact with each other. Cells in the afferent
arteriole of the juxtaglomerular apparatus secrete
the enzyme renin into the blood, which activates the
renin-angiotensin system.K
keratin (ker 9 ̆a-tin) A protein that forms the
principal component of the outer layer of
the epidermis and of hair and nails.
ketoacidosis (ke 0 to- ̆a-s ̆ı-do 9 sis) A type of
metabolic acidosis resulting from the excessive
production of ketone bodies, as in diabetes
mellitus.
ketogenesis (ke 0 to-jen 9 ̆ı-sis) The production of
ketone bodies.
ketone (ke 9 t ̆on) bodies The substances derived
from fatty acids via acetyl coenzyme A in the
liver; namely, acetone, acetoacetic acid, and
b-hydroxybutyric acid. Ketone bodies are oxidized
by skeletal muscles for energy.
ketosis (ke-to 9 sis) An abnormal elevation in the
blood concentration of ketone bodies. This condition
does not necessarily produce acidosis.inositol triphosphate ( ̆ı-no 9 s ̆ı-tol tri-fos 9 f ̄at)
(IP 3 ) A second messenger in hormone action that
is produced by the cell membrane of a target cell in
response to the action of a hormone. This compound
is believed to stimulate the release of Ca^21 from the
endoplasmic reticulum of the cell.
insulin (in 9 s ̆u-lin) A polypeptide hormone
secreted by the beta cells of the islets of Langerhans
in the pancreas that promotes the anabolism of
carbohydrates, fat, and protein. Insulin acts to
promote the cellular uptake of blood glucose and,
therefore, to lower the blood glucose concentration;
insulin deficiency produces hyperglycemia and
diabetes mellitus.
integrins (in-te 9 grinz) A family of glycoproteins
that extend from the cytoskeleton, through the
plasma membrane of cells, and into the extra cellular
matrix. They serve to integrate different cells of a
tissue and the extracellular matrix, and to bind cells
to other cells, such as neutrophils to the endothelial
cells of capillaries for extravasation.
interferons (in 0 ter-fer 9 unz) Small proteins that
inhibit the multiplication of viruses inside host cells
and that also have antitumor properties.
interleukin-2 (in 0 ter-loo 9 kin-2) A lymphokine
secreted by T lymphocytes that stimulates the
proliferation of both B and T lymphocytes.
interneurons (in 0 ter-noor 9 onz) Those neurons
within the central nervous system that do not
extend into the peripheral nervous system. They are
interposed between sensory (afferent) and motor
(efferent) neurons; also called association neurons.
interoceptors (in 0 ter-o-sep 9 torz) Sensory receptors
that respond to changes in the internal environment
(as opposed to exteroceptors).
interphase The interval between successive cell
divisions, during which time the chromosomes are
in an extended state and are active in directing RNA
synthesis.
intestinal microbiota (mi 0 kro-bi-o 9 tah) The
microscopic organisms, principally bacteria, found in
the large intestine. The bacteria are often referred to
as commensal bacteria, because they do not harm the
human host and are in many ways beneficial. Also
called microflora.
interstitial (in-ter-stish 9 al) fluid The fluid outside
of the cells within a tissue or organ. Interstitial fluid
and blood plasma together compose the extracellular
fluid of the body. Also called tissue fluid.
intestino-intestinal (in 0 tes 9 t ̆ı-no-in-tes 9 t ̆ı-nal)
reflex The reflex in which overdistension to one
region of the intestine causes relaxation throughout
the rest of the intestine.
intrafusal (in 0 tr ̄a-fyoo 9 sal) fibers Modified muscle
fibers that are encapsulated to form muscle spindle
organs, which are muscle stretch receptors.
intrapleural (in 0 tr ̆a-ploor 9 al) space An actual or
potential space between the visceral pleura covering
the lungs and the parietal pleura lining the thoracic
wall. Normally, this is a potential space; it can
become real only in abnormal situations.
intrapulmonary (in 0 tr ̆a-pul 9 m ̆o-nar 0 e) space
The space within the air sacs and airways of the
lungs.
intron (in 9 tron) A noncoding nucleotide sequence
in DNA that interrupts the coding regions (exons) for
mRNA.
inulin (in 9 y ̆u-lin) A polysaccharide of fructose,
produced by certain plants, that is filtered by the
human kidneys but neither reabsorbed nor secreted.
The clearance rate of injected inulin is thus used to
measure the glomerular filtration rate.
in vitro (in ve 9 tro) Occuring outside the body, in a
test tube or other artificial environment.fox36375_glo_G1-G19.indd 10fox36375_glo_G1-G19.indd 10 2/4/15 12:29 PM2/4/15 12:29 PM