724
Glossary
diacylglycerol (DAG)
(dy-aa-syl-GLIS-er-ol)
second messenger that activates protein kinase
C, which then phosphorylates a large number
of other proteins
diapedesis
(dye-app-uh-DEE-suhs) passage
of leukocytes out of the blood and into the
surrounding tissue
diaphragm
(DY-ah-fram) dome-shaped skeletal
muscle sheet that separates the abdominal and
thoracic cavities; principal muscle of respiration
diastole
(dy-ASS-toh-lee) period of cardiac cycle
when ventricles are relaxing
diastolic pressure (DP)
(dy-ah-STAL-ik)
minimum blood pressure during cardiac cycle
diencephalon
(dy-en-SEF-ah-lon) core of anterior
part of brain; lies beneath cerebral hemispheres
and contains
thalamus
and
hypothalamus
differentiation
(dif-fer-en-she-AY-shun) process
by which unspecialized cells acquire specialized
structural and functional properties
diffusion
(dif-FU-shun) movement of molecules
from one location to another because of
random thermal molecular motion; net
diffusion always occurs from a region of
higher concentration to a region of lower
concentration
diffusion equilibrium
state during which
diffusion fl uxes in opposite directions are
equal; that is, the net fl ux equals zero
diffusion potential
voltage difference created by
net diffusion of ions
digestion
process of breaking down large particles
and high-molecular-weight substances into
small molecules
dihydropyridine (DHP) receptor
(die-hydro-
PEER-a-deen) nonconducting calcium
channels in the T-tubule membranes of skeletal
muscle cells, which act as voltage sensors in
excitation-contraction coupling
dihydrotestosterone
(dy-hy-droh-tes-TOS-ter-
own) steroid formed by enzyme-mediated
alteration of testosterone; active form of
testosterone in certain of its target cells
1,25-dihydroxyvitamin D (1,25-OH
2
D)
(1-25-dy-hy-DROX-ee-vy-tah-min DEE)
hormone that is formed by kidneys and is the
active form of vitamin D
diiodotyrosine (DIT)
a doubly iodinated
tyrosine molecule that is an intermediate in the
formation of thyroid hormones
2,3-diphosphoglycerate (DPG)
(2-3-dy-fos-
foh-GLISS-er-ate) substance produced by
erythrocytes during glycolysis; binds reversibly
to hemoglobin, causing it to release oxygen
disaccharide
(dy-SAK-er-ide) carbohydrate
molecule composed of two monosaccharides
disc
layer of membranes in outer segment of
photoreceptor; contains photopigments
dissociation
separation from
distal
(DIS-tal) farther from reference point;
compare
proximal
distal convoluted tubule
portion of kidney
tubule between loop of Henle and collecting
duct system
disulfi
de bond
R—S—S—R
diuresis
(dy-uh-REE-sis) increased urine excretion
diuretic
(dy-uh-RET-ik) substance that inhibits
fl uid reabsorption in renal tubule, thereby
increasing urine excretion
diurnal
(dy-URN-al) daily; occurring in a 24-h
cycle
divergence
(dy-VER-gence) (neuronal) one
presynaptic neuron synapsing upon many
postsynaptic neurons; (of eyes) turning of eyes
outward to view distant objects
dl
deciliter; 0.1 L
dominant follicle
most mature developing follicle
in the ovary from which the mature egg is
ovulated
dopamine
(DOPE-ah-meen) biogenic amine
(catecholamine) neurotransmitter and
hormone; precursor of epinephrine and
norepinephrine;
see also
prolactin-inhibiting
hormone
dorsal
(DOR-sal) toward or at the back
dorsal column pathway
ascending pathway for
somatosensory information; runs through
dorsal area of spinal white matter
dorsal horn and ventral horn
regions of gray
matter in the spinal cord containing cell bodies
of interneurons and motor neurons
dorsal respiratory group
neurons in the
medullary respiratory center that fi re during
inspiration
dorsal root
group of afferent nerve fi bers that
enters dorsal region of spinal cord
dorsal root ganglion
group of sensory nerve cell
bodies that have axons projecting to the dorsal
horn of the spinal cord
down-regulation
decrease in number of target-
cell receptors for a given messenger in response
to a chronic high concentration of that
messenger;
compare
up-regulation
dual innervation
(in-ner-VAY-shun) innervation
of an organ or gland by both sympathetic and
parasympathetic nerve fi bers
duodenum
(due-oh-DEE-num) fi rst portion of
small intestine (between stomach and jejunum)
dura mater
thick, outermost membrane
(meninges) covering the brain
dynein
(DIE-neen) motor protein that uses the
energy from ATP to transport attached cellular
cargo molecules along microtubules
dynorphin
(dye-NOR-fi n) one of a group
of endogenous opioid peptides that act as
neuromodulators in the brain
E
eardrum
see
tympanic membrane
eccentric contraction
muscle activity that is
accompanied by lengthening of the muscle
generally by an external load that exceeds
muscle force
ECG lead
combination of a reference electrode
(designated negative) and a recording electrode
(designated positive) that are placed on the
surface of the body and provide a “view” of the
electrical activity of the heart
edema
(ed-DEE-mah) accumulation of excess
fl uid in interstitial space
EEG arousal
transformation of EEG pattern from
alpha to beta rhythm during increased levels of
attention
effector
(ee-FECK-tor) cell or cell collection
whose change in activity constitutes the
response in a control system
efferent
(EF-er-ent) carrying away from
efferent arteriole
renal vessel that conveys blood
from glomerulus to peritubular capillaries
efferent division (PNS)
neurons in the
peripheral nervous system that project out of
the central nervous system
efferent neuron
neuron that carries information
away from CNS
efferent pathway
component of refl ex arc that
transmits information from integrating center
to effector
egg
female germ cell at any of its stages of
development
eicosanoid
(eye-KOH-sah-noid) general term
for modifi ed fatty acids that are products
of arachidonic acid metabolism (cyclic
endoperoxides, prostaglandins, thromboxanes,
and leukotrienes); function as paracrine/
autocrine agents
ejaculation
(ee-jak-you-LAY-shun) discharge of
semen from penis
ejaculatory duct
(ee-JAK-you-lah-tory)
continuation of vas deferens after it is joined by
seminal vesicle duct; joins urethra in prostate
gland
ejection fraction (EF)
the ratio of stroke volume
to end-diastolic volume; EF = SV/EDV
elastic recoil
tendency of an elastic structure to
oppose stretching or distortion
elastin fi
ber
a protein with elastic or springlike
properties; found in large arteries and in the
airways
electrical force
force that causes charged particles
to move toward regions having an opposite
charge and away from regions having a like
charge
electrical potential (
E
)
(or electric potential
difference)
see
potential
electrical signal
graded potential or action
potential
electrical synapse
(SIN-apse) synapse at which
local currents resulting from electrical activity
fl ow between two neurons through gap
junctions joining them
electrocardiogram (ECG, EKG)
(ee-lek-troh-
KARD-ee-oh-gram) recording at skin surface
of the electrical currents generated by cardiac
muscle action potentials
electrochemical difference
force determining
direction and magnitude of net charge
movement; combination of electrical and
chemical gradients
electrochemical gradient
the driving force across
a plasma membrane that dictates whether an
ion will move into or out of a cell; established
by both the concentration difference and
the electrical charge difference between the
cytosolic and extracellular surfaces of the
membrane
electrode
(ee-LEK-trode) probe used to stimulate
electrically, or record from, the body surface
or a tissue
electroencephalogram (EEG)
(eh-lek-troh-en-
SEF-ah-loh-gram) recording of brain electrical
activity from scalp
electrogenic pump
(elec-troh-JEN-ik) active
transport system that directly separates
electrical charge, thereby producing a potential
difference
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