Glossary
745
voltage-gated channel
cell-membrane ion
channel opened or closed by changes in
membrane potential
voluntary movement
consciously carried-out
motions mediated by the somatic nervous
system and skeletal muscle contraction
vomiting center
neurons in brainstem medulla
oblongata that coordinate vomiting refl ex
von Willebrand factor (vWF)
(von-VILL-ih-
brand) plasma protein secreted by endothelial
cells; facilitates adherence of platelets to
damaged vessel wall
vulva
(VUL-vah) female external genitalia; mons
pubis, labia majora and minora, clitoris,
vestibule of vagina, and vestibular glands
W
waste product
product from a metabolic reaction
or series of reactions that serves no function
water diuresis
increase in urine fl ow due
to increased fl uid output (usually due to
decreased secretion or action of vasopressin)
water-soluble vitamin
see
vitamin
wavelength
distance between two successive wave
peaks in oscillating medium
weak acid
acid whose molecules do not
completely ionize to form hydrogen ions when
dissolved in water;
compare
strong acid
Wernicke’s area
brain area involved in language
comprehension
white matter
portion of CNS that appears white
in unstained specimens and contains primarily
myelinated nerve fi bers
white muscle fi
ber
muscle fi ber lacking
appreciable amounts of myoglobin
withdrawal refl
ex
bending of those joints that
withdraw an injured part away from a painful
stimulus
Wolffi
an duct
(WOLF-ee-an) part of embryonic
duct system that, in male, remains and develops
into reproductive system ducts, but in female,
degenerates
work
measure of energy required to produce
physical displacement of matter;
see also
external work, internal work
working memory
short-term memory storage
process serving as initial depository of
information
X
X chromosome
see
sex chromosome
Y
Y chromosome
see
sex chromosome
Z
Z line
structure running across myofi bril at each
end of striated muscle sarcomere; anchors one
end of thin fi laments and titin
zona pellucida
(ZOH-nah peh-LOO-sih-
dah) thick, clear layer separating egg from
surrounding granulosa cells
zonular fi
ber
connecting the ciliary muscles with
the lens of the eye
zygote
(ZY-goat) a newly fertilized egg
zymogen
(ZY-moh-jen) enzyme precursor
requiring some change to become active
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