T tegulatory cell a rype of immune (T) ce[ that
emission ofhat frorn the surlacc
eye movement sleep raa
REM
ofrn
sleep
adapting receptor scffory receptor that
for a briefperiod at the onsct and/or offset
of
reaction slowest reaction in metabolic
rate-limiting enzyme
hyperemia (hye-per-EE-me-ah ) rransicnr
in blood flow following release ofocclusion
; catalyzed by
supply
field (ofneuron)
area ofbody that,
results in activity in tltat neuron
if
relaxation relaxation of the smooth
of th stomach (fundus and body) whcn
is swallowed; mediated by parasympatheric
in t}te enteric nerve plexuses
(for messengers) protein cither on cell
vt in the cltosol, or in the nucleus that
ur ur! lJlvovr,
\/r ur Lr!! uurtluD
urdt
a chemical messenger such as a
hormone or
itter and mcdiatcs its rctionsl
system) specialized peripheral cnding
neuron) or separate ccll intimatcly
with it, that detects changcs in some
ofenvironment
actftation change in receptor conlormation
by combination of mcssenger with receptor
&eeneitization temporary inability
to respond to its ligand due to pr"ior
binding
erdorytools thc specific r.rpt*c
in the extracellular fluid by regions of
membrane that invaginatc md fbrm
vesicles
potentlal
graded potcntial thnt ariltes
neuron ending, or a specializeel cell
tely associated with it, in responsc
tcr
tyrosine kinaee the m{jor typc ofrsccptol
that is itselfan enzyme; thc$c rcccptor$
plasma membranes and rcspond tcl uuny
water-soluble chemical messeugcrs
innerr"ation inhibition of motor neurons
muscles whose contraction would erppose
movement
binding ofantigen to receptor spccific
antigen on lymphocJ're surfacc
activation ofadditional cclls in rcsponsc
stimulus strength; increasing the
of active motor units in a musclc
short segment oflarge intestine bcnvcen
colon and anus
fbcr muscle fiber having high oxidative
and largc amount ofmyoglobin
flex) biological control svstem
stimulus with response and mediated
arc
neuml or hormonal components that
a rcflex; usually includes receptor, affer.ent
intcgrating center, efferent pathrvay, and
bending oflight rays when passing
compartments ofdiffercnt density, as liom
thc cornca ofthe eyes
1rcrlod (of cardiac musde)
minimize the likelihood of autoirnmunity
relative re&actory period time during which
excitable membranc rvill produce action potcntial
but only ro a stimulus ofgreater strength than the
usual thrcshold strength
relaxation return ofmusclc to a low fbrce-generating
state, ceused by dctachment ofcross-bridges
relaxin hormonc secreted by the ovary before
parturition
REM sleep (rcm)
sleep state associated
with small,
rapid EEG oscillations, complete loss of tone in
postural muscles, and dreuning; also called ra,pid
,&op
etnent sleeh
p
orad.oxi cal sleep
renal (REE-nal) pertaining to kidneys
renal colpuscle combination of glomerulus antl
Bowman's capsulc
renal cortex outcr portion ofthe kidney
renal medulla inner portion of the kidncy
renal pelvis cavity at base ofeach lddney; receives
urine from collecting-duct system and empties it
into ureter
tenal plasma flow thc total anount olplasma (blood
minus red cell volumc) that passes through both
kidncys per: unit time
renln (REE-nin) pr:ptide secreted by lddneys; acts as
an enzymc that catalyzes splitting offofangiotensin
docs not respond to a stinulus that
rcfractory
relative reft actory period
elte site on protcin that interacts
molecule; alters functional site
I
fiom angiotcnsinogcn in plasma
fenhr-anglotensin system hormonll system
cousisting of rcnin-stimulatcd angiotensin I
prodnction follor,vcd by convcrsion to angiotcnsin
by rngiotensin-convcrting cnzymc
II
rclrohdze retun'l tran$l'nclrbranc potentitl to its
re$tiug level
recldual volurne (RV) air volurne rcmdning in liurgs
at'ter mirxinrtrl cxpiration
foslstanc (R) hirrdrancc to movcutcllt thror,rgh
l Prrricnhr sntrstancc, rulrc, of r4rcrring
reeplfatoly bronchlole lorgest lrrlnch of the
r(|spiratory rrcc
ir"r
r a ti c a la.r fo r rn a.t i o n
reticulocyte (ruh-Tll(-you-low-site) narne given
to irnnratur rcd blood cclls that have a rvcblike
pattern in the cytosol due to the pcrsistence ol
ribosomes
retina thin layer ofneural tissue lining back ofeyeball;
contains receptors for vision
r:etinal (ret-in-Al,) forrn of vitarnin A that comporcnt fbrms
chromophore of photopigrnent
retrograde movement ofa substance or action
potential backward along a nellron, from axon
terminals toward the cell lrody and dcndrites
eye
r.vhich the nnits ofSa$ sxchonse
(llveoli) appear
respfuatolT cycle ch;:rnges in thc lung volumcs fr<>rrr
thc lrcginning ofan inspiration, including the
cxpiration, to thc bcgimring of the next ir-rspiration
reopfuatory physiolog5r thc study ofthc rcspirarory
system, including its structurcs and fltnctiolt$ a$d
rcgulndon
reeplratory purnp mechanisnt wherclry reductions
in intrathoracic pressurc dnring thc breathing cyclc
tend to fhvclr the return of[:l<iod to the heart from
pcripheral veins
reepiratoqy quotient (RQ) rario of carbon dioxide
produced to oxygen consumed during tretabolisn-r
respiratory rate numbcr ofbreaths per minutc
respfuatorT rhythm generator neural network in
thcfirainstem that generates output to thc phrenic
resplratory system the anatonical pathway of air
florn the atmosphere to the alvcoli
respiratoty zone portion ofairways from beginning
ofrespiratory bronchioles to alveoli; contains alveoli
across rvhich gas exchange occurs
resting membrane potential voltagc difference
between inside and outside ofcell in absencc
ofexcitatory or inhibitory stimulatior.r; also called
resting potentinl
ee) time during which an excitable
causes fesponse; J, e nko absolute
pathways and from other CNS regions; also called
is
believed to suppress immune fuirction a::d may
rest-ordigest state homeostatic state characteristic
of parasympathctic nen'ous system activation
rete testes (REE-tee TES-teez) network ofcanals at
the ends ofthe serniniferous tubules in thc testes
reticular activating system (RAS) extensivc neuron
network extending through brainstcm core; rcceives
and integrates information from many afferent
reuptake acdve process that recaptures excess
secreted neurotransmittcr back into the presynaptic
cell; can be inhibitcd rvith drugs
reversible reaction chemical reaction in which cnergy
rclcasc is snraJl cnough for rcverse rerction to occur
readily ; cowpare irreversible reaction
Rh factor group of erytJrroryte plasma membrane
antigens that may (Rh*)or rnay not (Rh-) be
present
rhodopsin (roh-DOP-sin) photopigment in rods
ribonucleic acid (RNA) (rye-boh-noo-KlAy-ik)
single-stranded nucleic acid involved in transcription
ofgenetic infonnation and trarslation ofthat
information into protein structurei contain$ t}re
sugar ribose; see also messenger RNA, ribosomal
RNA, transfbr RNA
ribose the sugar backbone ofRNA
ribosomal RNA (IRNA) (rye-boh-SOME-at) type
of RNA used in ribosome asse mbly; becomes part
of ribosome
ribosome (RlT- boh -some ) cy"toplasm ic particle that
mcdiates linking together of amino acids to form
proteins; attached to endoplasmic reticulum as
bound ribosome, or suspended in cytoplasm as free
ribosome
rigor mortis (rig-or MOR-tiss)
stiflhcss of skelctal
muscles after death due to failure ofcross-bridges to
dissociate liom actin because ofthe loss of-ATp
RNA polyrnerase (poh-LlM-uh-rasc) enzyme
that forms RNA by joining together appropriate
nucleotides aftcr they have lrase-paircd to DNA
rod one oftwo receptor types fbr photic energy;
contains the photopigment rhodopsin
round window membrane-covered opcning in the
cocl-rlea that responds
to fluid movcmcllt in the
scala
wmpar-ri
{yanodine receptor calcium-release channel found
in the lateral sacs of'the sarcoplasmic reticulum in
skeletal muscle cells
s
saccade (sah-K{AD) short, jerking eycball movemct)t
saccule structure in thc scmicirculnr carrals that
responds to changcs in linear movcment ofthe
head by mcchanical firrccs on otoliths lercatecl on its
surface
sali\r, wttcry solution ofsdts nud protcins, including
mucins and $lnyla$e, sccrcted by salivary glalds
salivarT gland onc of'thrcc pnirs of'cxocrinc glands
around thc mouth that prodncc saliva
calt appedtc desire for salt, consisting ofheelonistir:
and rcgulatory conrpotcnts
saltatory conducdon propagatiou of action
potcntial$ along * nryclinated axon such that tlrc
action potcntials jump f?om onc node of Ranvicr in
the myclin sheath to thc ncxt
saroofiter! (SAR-kuh-mecr) rcpeating sruc&ral unit
of myofibril; composcd of thick and thin filamcnts;
extends betwcen two adjaccnt Z lines
nto