Glossary
737
plasma protein
most are albumins, globulins, or
fi brinogen
plasmin
(PLAZ-min) proteolytic enzyme able to
decompose fi brin and thereby to dissolve blood
clots
plasminogen
(plaz-MIN-oh-jen) inactive
precursor of plasmin
plasminogen activator
any plasma protein that
activates proenzyme plasminogen
plasticity
(plas-TISS-ih-tee) ability of neural tissue
to change its responsiveness to stimulation
because of its past history of activation
platelet
(PLATE-let) cell fragment present in
blood; plays several roles in blood clotting
platelet activation
changes in the metabolism,
shape, and surface proteins of platelets that
begin the clotting process
platelet aggregation
(ag-reh-GAY-shun) positive
feedback process resulting in platelets sticking
together
platelet factor (PF)
phospholipid exposed in
membranes of aggregated platelets; important
in activation of several plasma factors in clot
formation
platelet plug
blockage of a vessel by activated,
adherent platelets
pleura
(PLUR-ah) thin cellular sheet attached to
thoracic cage interior (
parietal pleura
) and,
folding back upon itself, attached to lung
surface (
visceral pleura
); forms two enclosed
pleural sacs
in thoracic cage
pleural sac
membrane enclosing each lung
pluripotent hematopoietic stem cells
(plur-ih-
POH-tent) single population of bone marrow
cells from which all blood cells are descended
pneumotaxic center
(NOO-moh-tak-sik) area
of the upper pons in the brain that modulates
activity of the apneustic center
podocyte
epithelial cells lining Bowman’s capsule,
whose foot processes form fi ltration slits
polar covalent bond
covalent chemical bond
in which two electrons are shared unequally
between two atoms; atom to which the
electrons are drawn becomes slightly negative,
while other atom becomes slightly positive;
also called
polar bond
polarized
(POH-luh-rized) having two electrical
poles, one negative and one positive
polar molecule
pertaining to molecule or region
of molecule containing polar covalent bonds
or ionized groups; part of molecule to which
electrons are drawn becomes slightly negative,
and region from which electrons are drawn
becomes slightly positive; molecule is soluble
in water
polymer
(POL-ih-mer) large molecule formed
by linking together smaller similar subunits
polymodal neuron
sensory neuron that
responds to more than one type of stimulus
polymorphonuclear granulocyte
(pol-ee-morf-
oh-NUK-lee-er GRAN-you-loh-site) subclass
of leukocytes consisting of eosinophils,
basophils, and neutrophils
polypeptide
(pol-ee-PEP-tide) polymer consisting
of amino acid subunits joined by peptide
bonds; also called
peptide
or
protein
polysaccharide
(pol-ee-SAK-er-ide)
large carbohydrate formed by linking
monosaccharide subunits together
polysynaptic refl
ex
(pol-ee-sih-NAP-tik) refl ex
employing one or more interneurons in its
refl ex arc
polyunsaturated fatty acid
fatty acid that
contains more than one double bond
pons
large area of the brainstem containing many
nerve axons
pontine respiratory group
neurons in the pons
that modulate respiratory rhythms
pool
the readily available quantity of a substance in
the body; often equals amounts in extracellular
fl uid
portal system
a type of circulation characterized
by two capillary beds connected by veins
called portal veins
portal vein
vessel through which blood from
several abdominal organs fl
ows to the liver
portal vessel
any blood vessel that links two
capillary networks
positive balance
gain of substance exceeds
loss, and amount of that substance in body
increases;
compare
negative balance
positive feedback
characteristic of control
systems in which an initial disturbance sets off
train of events that increases the disturbance
even further;
compare
negative feedback
postabsorptive state
(post-ab-SORP-tive)
period during which nutrients are not being
absorbed by gastrointestinal tract and energy
must be supplied by body’s endogenous
stores
posterior
toward or at the back
posterior pituitary
portion of pituitary from
which oxytocin and vasopressin are released
postganglionic neuron
(post-gang-glee-ON-ik)
autonomic-nervous-system neuron or nerve
fi ber whose cell body lies in a ganglion;
conducts impulses away from ganglion toward
periphery;
compare
preganglionic neuron
postsynaptic density
area in the postsynaptic
cell membrane that contains neurotransmitter
receptors and structural proteins important for
synapse function
postsynaptic neuron
(post-sin-NAP-tik) neuron
that conducts information away from a synapse
postsynaptic potential
local potential that arises
in postsynaptic neuron in response to activation
of synapses upon it;
see also
excitatory
postsynaptic potential, inhibitory postsynaptic
potential
postural refl
ex
refl ex that maintains or restores
upright, stable posture
potential
(or potential difference) voltage
difference between two points;
see also
action
potential, graded potential
potential difference
a difference in charge
between two points
potentiation
(poh-ten-she-AY-shun) presence of
one agent enhances response to a second such
that fi nal response is greater than sum of the
two individual responses
potocytosis
(poh-toe-si-toe-sis) a type of receptor-
mediated endocytosis in which vesicle contents
are delivered directly to the cytosol
power stroke
the step of a cross-bridge cycle
involving physical rotation of the globular head
preattentive processing
neural processes that
occur to direct our attention to a particular
aspect of the environment
pre-Botzinger complex
neurons of the ventral
respiratory group in the medulla that are the
respiratory rhythm generator
precapillary sphincter
(SFINK-ter) smooth-
muscle ring around capillary where it exits
from thoroughfare channel or arteriole
preganglionic neuron
autonomic-nervous-
system neuron or nerve fi ber whose cell body
lies in CNS and whose axon terminals lie in a
ganglion; conducts action potentials from CNS
to ganglion;
compare
postganglionic neuron
preinitiation complex
a group of transcription
factors and accessory proteins that associate
with promoter regions of specifi c genes; the
complex is required for gene transcription to
commence
preload
the amount of fi lling of ventricles just
prior to contraction; the end-diastolic volume
premotor area
region of the cerebral cortex
found on the lateral sides of the brain in
front of the primary motor cortex; involved
in planning and enacting complex muscle
movements
pressure natriuresis
increase in sodium excretion
induced by a local action within the renal
tubules due to an increase in the arterial
pressure within the kidney
presynaptic facilitation
(pre-sin-NAP-tik)
excitatory input to neurons through synapses
at the nerve terminal
presynaptic inhibition
inhibitory input to
neurons through synapses at the nerve terminal
presynaptic neuron
neuron that conducts action
potentials toward a synapse
primary active transport
active transport in
which chemical energy is transferred directly
from ATP to transporter protein
primary cortical receiving area
region of
cerebral cortex where specifi c ascending
pathways end; somatosensory, visual, auditory,
or taste cortex
primary lymphoid organ
organs that supply
secondary lymphoid organs with mature
lymphocytes; bone marrow and thymus
primary motivated behavior
behavior related
directly to achieving homeostasis
primary motor cortex
see
motor cortex
primary oocyte
(OH-uh-site) female germ cell
that undergoes fi rst meiotic division to form
secondary oocyte and polar body
primary protein structure
the amino acid
sequence of a protein
primary response gene (PRG)
gene infl uenced
by transcription factors generated in response
to fi rst messengers
primary RNA transcript
an RNA molecule
transcribed from a gene before intron removal
and splicing
primary spermatocyte
(sper-MAT-uh-site)
male germ cell derived from spermatogonia;
undergoes meiotic division to form two
secondary spermatocytes
primordial follicle
(FAH-lik-el) an immature
oocyte encased in a single layer of granulosa cells
procedural memory
the memory of how to do
things
process
long extension from neuron cell body
product
molecule formed in enzyme-catalyzed
chemical reaction
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