966
GLOSSARY
neuronal pool
(nu
ro-nal po
ˉ
o
ˉ
l)
Accumulation of nerve cells. p. 374
neuropeptide
(nu
ro-pep
tı¯d)
Peptide
in the brain that functions as a
neurotransmitter or neuromodulator.
p. 374
neurosecretory cell
(nu
ro-se-kre
to-re
sel)
Cell in the hypothalamus that
functions as a neuron at one end but
like an endocrine cell at the other,
by receiving messages and secreting
the hormones ADH and oxytocin.
p. 493
neurotransmitter
(nu
ro-trans-mit
er)
Chemicals that an axon end secretes
that stimulates a muscle F
ber to
contract or a neuron to F
re an
impulse. p. 289
neutral
(nu
tral)
Neither acidic nor
alkaline; pH 7. p. 59
neutron
(nu
tron)
Electrically neutral
subatomic particle. p. 52
neutrophil
(nu
tro-F l)
Type of
phagocytic white blood cell. p. 531
niacin
(ni
ah-sin)
Vitamin of the
B-complex group; nicotinic acid.
p. 714
nitrogen balance
(ni
tro-jen bal
ans)
Condition in which the amount of
nitrogen ingested equals the amount
excreted. p. 705
node of Ranvier
(no
¯d of Ron
vee-ay)
Short region of exposed
(unmyelinated) axon between
Schwann cells on neurons of the
peripheral nervous system. p. 356
nondisjunction
(non
dis-jungk
shun)
A
pair of chromosomes that remains
together rather than separating
during meiosis. p. 929
nonprotein nitrogenous substance
(non-
pro
te
¯n ni-troj
e
˘-nus sub
stans)
A
nitrogen-containing molecule that is
not a protein. p. 537
norepinephrine
(nor
ep-ı˘-nef
rin)
Neurotransmitter released from the
axons of some nerve F
bers. p. 301
normal range
(nor
mal ra
¯nj)
Measurements or values obtained
from a statistical sample of the
healthy population for reference or
comparison. p. 9
nuclear envelope
(nu
kle-ar en
ve
˘-lo
¯p)
Membrane surrounding the cell
nucleus and separating it from the
cytoplasm. p. 89
nuclear pore
(nu
kle-ar po
¯r)
Protein-
lined channel in the nuclear
envelope. p. 89
nuclease
(nu
kle-a
¯s)
Enzyme that
catalyzes decomposition of nucleic
acids. p. 672
nucleic acid
(nu-kle
ik as
id)
A
molecule that is composed of
nasal septum
(na
zal sep
tum)
Wall of
bone and cartilage that separates the
nasal cavity into two parts. p. 737
nasopharynx
(na
zo-far
ingks)
Part of
the pharynx posterior to the nasal
cavity. p. 663
natural killer cell
(nat
u-ral kil
er sel)
Lymphocyte that bursts an infected
or cancerous cell. p. 627
negative feedback
(neg
ah-tiv fe
¯d
bak)
A mechanism that restores a
biochemical or other balance
in which build up of a product
suppresses its synthesis. p. 9
neonatal
(ne
o-na
tal)
The F
rst four
weeks after birth. p. 904
nephron
(nef
ron)
±unctional unit
of a kidney, consisting of a renal
corpuscle and a renal tubule. p. 779
nerve
(nerv)
Bundle of nerve F
bers.
p. 354
nerve cell
(nerv sel)
Neuron. p. 354
nerve F
ber
(nerv F
ber)
Axon of a
neuron. p. 354
nerve impulse
(nerv im
puls)
Depolarization and repolarization
along a nerve F
ber. p. 354
nerve tract
(nerv trakt)
Long bundle
of nerve F
bers in the CNS having
the same origin, function, and
termination. p. 389
nervous tissue
(ner
vus tish
u)
Neurons
and neuroglia composing the brain,
spinal cord and nerves. p. 164
net F
ltration pressure
(F
l-tra
shun
presh
ur)
Equal to the hydrostatic
pressure of the blood entering the
glomerulus minus the pressure of
the opposing forces (the hydrostatic
pressure in the glomerular capsule
and the plasma osmotic pressure of
the blood in the glomerulus). p. 788
neurilemma
(nur
ı¯-lem
ah)
Sheath on
certain nerve F
bers, formed from
Schwann cells. p. 356
neuroF
bril
(nu
ro-F
bril)
±ine
cytoplasmic thread that extends
from the cell body into the process
of a neuron. p. 356
neuroglia
(nu-ro
gle-ah)
Specialized
cells of the nervous system that
produce myelin, communicate
between cells, maintain the ionic
environment, provide growth factors
that support neurons, and provide
structural support. p. 354
neuromodulator
(nu
ro-mod
u-la
¯-tor)
Substance that alters a neuron
s re-
sponse to a neurotransmitter. p. 374
neuromuscular junction
(nu
ro-mus
ku-
lar jungk
shun)
Synapse between a
motor neuron and a skeletal muscle
F
ber; myoneural junction. p. 290
neuron
(nu
ron)
Nerve cell. p. 354
multiple motor unit summation
(mul
tı˘-
pl mo
tor u
nit sum-ma
¯
shun)
Sustained muscle contraction of
increasing strength in response
to input from many motor units.
p. 298
multipolar neuron
(mul
tı¯-po
lar
nu
ron)
Nerve cell that has many
processes emanating from its cell
body. p. 360
muscle F
ber
(mus
el F
ber)
Muscle cell.
p. 163
muscle impulse
(mus
el im
puls) Impulse
propagated along the sarcolemma into
the transverse tubules. p. 290
muscle spindle
(mus
el spin
dul)
ModiF ed skeletal muscle F
ber that
can respond to changes in muscle
length. p. 444
muscle tissue
(mus
el tish
u)
Contractile tissue of F
laments of
actin and myosin, which slide past
each other, shortening cells. p. 163
muscle tone
(mus
el to
¯n)
Contraction
of some F
bers in skeletal muscle at
any given time. p. 298
mutagen
(mu
tah-jen)
Agent that can
cause mutations. p. 136
mutant
(mu
tant)
Allele for a certain
gene that has been altered from the
“normal” condition. p. 920
mutation
(mu-ta
shun)
Change in a
gene. p. 135
myelin
(mi
e
˘-lin)
±atty material that
forms a sheathlike covering around
certain nerve F
bers. p. 356
myocardium
(mi
o-kar
de-um)
Muscle
tissue of the heart. p. 555
myoF
bril
(mi
o-F
bril)
Contractile
F bers in muscle cells. p. 287
myoglobin
(mi
o-glo
bin)
Pigmented
compound in muscle tissue that
stores oxygen. p. 294
myogram
(mi
o-gram)
Recording of a
muscular contraction. p. 296
myometrium
(mi
o-me
tre-um)
Layer
of smooth muscle tissue within the
uterine wall. p. 854
myopia
(mi-o
pe-ah)
Nearsightedness.
p. 472
myosin
(mi
o-sin)
Protein that, with
actin, contracts and relaxes muscle
F bers. p. 287
N
nail
(na
¯l)
Horny plate at the distal end
of a F
nger or toe. p. 177
nasal cavity
(na
zal kav
ı˘-te)
Space in
the nose. p. 12
nasal concha
(na
zal kong
kah)
Shell-
like bone extending outward from
the wall of the nasal cavity; a
turbinate bone. p. 737
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