A&P II FINAL Questions With Complete Solutions.

A&P II FINAL Questions With Complete Solutions. Virtually lall lof lthe lprotein lor lamino lacid-based lhormones lexert ltheir leffects lthrough lintracellular l__________. a. lions b. ldeactivators c. lsecond lmessengers d. lnucleotides l- l l l lcorrect lanswer.c. lsecond lmessengers Chemical lSubstances lsecreted lby lcells linto lthe lextracellular lfluids lthat lregulate lthe lmetabolic lfunction lof lother lcells lin lthe lbody lare lcalled l___________. a. lproteins b. lantibodies c. lhormones d. lenzymes l- l l l lcorrect lanswer.c. lhormones The lmaster lgland lof lthe lendocrine lsystem lis lthe_________. a. lendocrine b. lpituitary c. ladrenal d. lthyroid l- l l l lcorrect lanswer.b. lpituitary The lsecretion lof lhormones lin lresponse lto lchanging lblood llevels lof lions lis lknown las l_____. a. lneural lstimulus b. lhormonal lstimulus c. lhumoral lstimulus d. lionic lstimulus l- l l l lcorrect lanswer.c. lhumoral lstimulus The lhormone lthat lhas lthe lgreatest leffect lon lthe lmetabolic lrate lis l_____________. a. lgrowth lhormone b. laldosterone c. lthyroid d. lcortisol l- l l l lcorrect lanswer.c. lthyroid When lblood lglucose llevels lfall, lthe lpancreas lreleases l________. a. linsulin b. lmelatonin c. lglucose d. lglucagon l- l l l lcorrect lanswer.d. lglucagon When lparathyroid lhormone lis lreleased a. lblood lcalcium llevels lfall b. losteoclasts lare lactivated c. lcalcitonin lis linhibited d. lcalcium lchannels lare lblocked l- l l l lcorrect lanswer.b. losteoclasts lare lactivated The lcells lwith lthe lmost lreceptors lfor lgrowth lhormones lare a. lliver b. lnerves c. lbones d. lblood lvessels l- l l l lcorrect lanswer.c. lbones Steroid lhormones linfluence lother lcells lby l a. lactivating lcyclic lAMP b. lentering lthe lnucleus lof lthe lcell land laltering lthe lexpression lof lthe lgene c. lbinding lspecific lreceptors land lactivating lG lproteins d. lstimulating lthe luptake lof lglucose l- l l l lcorrect lanswer.b. lentering lthe lnucleus lof lthe lcell land laltering lthe lexpression lof lthe lgene The lmajor lplasma lprotein lis a. lthrombin b. lalbumin c. lfibrin d. lfibrinogen l- l l l lcorrect lanswer.b. lalbumin This ltype lof lleukocyte lproduces lantibodies a. lneutrophil b. leosinophil c. lmonocyte d. llymphocyte l- l l l lcorrect lanswer.d. llymphocyte Which lof lthe lfollowing lis lnot la lphase lof lerythropoiesis a. lsynthesis lof lhemoglobin b. lproduction lof lvacuoles c. lejection lof lthe lerythrocyte lnucleus d. lproduction lof lribosomes l- l l l lcorrect lanswer.b. lproduction lof lvacuoles Red lblood lcells lcontain l___% lhemoglobin a. l50 b. l82 c. l97 d. l100 l- l l l lcorrect lanswer.c. l97 Which lof lthe lfollowing lis lnot la lfunction lof lblood a. lcontrolling lendocrine lglands b. ltransporting loxygen c. ldistributing lheat d. lproducing lantibodies l- l l l lcorrect lanswer.a. lcontrolling lendocrine lglands What lorgan lin lthe lbody lregulates lerythropoeisis? a. lbrain b. lkidney c. lpancreas d. lliver l- l l l lcorrect lanswer.b. lkidney Which lof lthe lfollowing lis lnot la lphase lof lhemostasis? a. lvascular lspasm b. lfibrinolysis c. lcoagulation d. lplatelet lplug lformation l- l l l lcorrect lanswer.b. lfibrinolysis The lfirst lphase lof lerythrocyte lproduction lis a. lhemoglobin lsynthesis b. lejection lof lthe lnucleus c. lribosome lsynthesis d. lreticulocyte lformation l- l l l lcorrect lanswer.c. lribosome lsynthesis All lblood lcells ldevelop lfrom l a. lhemocytoblasts b. lejection lof lthe lnucleus c. lmyeloid lstem lcells d. llymphoid lstem lcells l- l l l lcorrect lanswer.a. lhemocytoblasts Which lof lthe lfollowing lcells lcould ldevelop lfrom la llymphoid lstem lcell? a. llymphocyte b. lerythrocyte c. lmonocyte d. lany lblood lcell l- l l l lcorrect lanswer.a. llymphocyte The llife lspan lof la lred lblood lcell lis labout a. l4 ldays b. l4 lweeks c. l4 lmonths d. l4 lyears l- l l l lcorrect lanswer.c. l4 lmonths After lhemoglobin lis lbroken ldown, lwhat lpart lof lit lenters lthe lliver land lbecomes lbile, lwhich lhelps lus ldigest lfood? a. lglobin b. lbilirubin c. lheme d. lferritin l- l l l lcorrect lanswer.b. lbilirubin Which lof lthe lfollowing lstructural lcharacteristics lcontribute lto lthe lfunction lof lred lblood lcells a. lbi-concave lshape b. lthey lcontain lmostly lhemoglobin c. lspectrin lin ltheir lplasma lmembrane d. lall lof lthe labove l- l l l lcorrect lanswer.d. lall lof lthe labove If lthe lvagal lnerves lto lthe lheart lwere lcut, lthe lresult lwould lbe lthat l________. a. lthe lAV lnode lwould lbecome lthe lpacemaker lof lthe lheart b. lthe lheart lrate lwould lincrease c. lparasympathetic lstimulation lwould lincrease, lcausing la ldecrease lin lheart lrate d. lthe lheart lwould lstop, lsince lthe lvagal lnerves ltrigger lthe lheart lto lcontract l- l l l lcorrect lanswer.b. lthe lheart lrate lwould lincrease the lcritical lfactor lcontrolling lstroke lvolume lis a. lpreload b. lafterload c. lcontractility d. lsympathetic lstimulation l- l l l lcorrect lanswer.a. lpreload Isovolumetric lcontraction l________. a. loccurs lonly lin lpeople lwith lheart lvalve ldefects b. loccurs lwhile lthe lAV lvalves lare lopen c. loccurs limmediately lafter lthe laortic land lpulmonary lvalves lclose d. lrefers lto lthe lshort lperiod lduring lventricular lsystole lwhen lthe lventricles lare lcompletely lclosed lchambers l- l l l lcorrect lanswer.d. lrefers lto lthe lshort lperiod lduring lventricular lsystole lwhen lthe lventricles lare lcompletely lclosed lchambers The lmost limportant lfactor lin lthe lregulation lof lthe lheart lrate lis a. lacidosis b. lautonomic lnervous lsystem lstimulation c. lstroke lvolume d. lextracellular lcalcium llevels l- l l l lcorrect lanswer.b. lautonomic lnervous lsystem lstimulation Which lof lthe lfollowing lis lnot la ldifference lbetween lskeletal land lcardiac lmuscle? a. lcardiac lmuscle lhas la llonger lrefractory lperiod b. lcardiac lmuscle lexhibits lautomaticity c. lcardiac lmuscle lhas lstriations d. lcardiac lmuscle lhas lgap ljunctions l- l l l lcorrect lanswer.c. lcardiac lmuscle lhas lstriations Cardiac lmuscle lcells luse l_____ lions lfor lthe lplateau lphase lof lthe laction lpotential. a. lcalcium b. lpotassium c. lsodium d. lchloride l- l l l lcorrect lanswer.a. lcalcium Pressure lin lthe lventricles lis lgreatest lwhen a. lthey lare lfilling b. lthey lare lrelaxed c. lthey lare lin ldiastole d. lthey lare lin lsystole l- l l l lcorrect lanswer.d. lthey lare lin lsystole During lventricular lsystole, lAV lvalves lclose lbecause a. latrial lpressure ldecreases b. latrial lpressure lincreases c. lventricular lpressure ldecreases d. lventricular lpressure lincreases l- l l l lcorrect lanswer.d. lventricular lpressure lincreases Blood lflow lwould lbe lincreased lby l a. ldecreasing lvessel ldiameter b. lincreasing lblood lvessel llength c. lincreasing lcardiac loutput d. ldecreasing lblood lpressure l- l l l lcorrect lanswer.c. lincreasing lcardiac loutput Fluids lwould lbe llikely lto lleave lor lfilter lout lof lthe lcapillary lif: a. losmotic lpressure lin lthe lcapillary lis lhigh b. lnet lhydrostatic lpressure lis lgreater lthan lnet losmotic lpressure c. lnet lhydrostatic lpressure lis lless lthan lnet losmotic lpressure d. lnet lfiltration lpressure lis lnegative l- l l l lcorrect lanswer.b. lnet lhydrostatic lpressure lis lgreater lthan lnet losmotic lpressure The lresistance lthat lhas lthe lmost leffect lon lblood lpressure lis lfrom a. llength lof lblood lvessels b. ldiameter lof lblood lvessels c. lviscosity lof lblood d. lnone lof lthese l- l l l lcorrect lanswer.b. ldiameter lof lblood lvessels Blood lflow lthrough lthe ltissues lis lresponsible lfor a. lurine lformation b. lremoval lof lwastes lfrom ltissue lcells c. lgas lexchange lin lthe llungs d. lall lof lthese l- l l l lcorrect lanswer.d. lall lof lthese Which ltype lof lblood lvessel lhas lthe lmost lelastic ltissue? a. larteries b. lveins c. lcapillaries d. lvenules l- l l l lcorrect lanswer.a. larteries True/False: lFever lis lseldom lbeneficial lbecause lit lspeeds lup lthe lcellular lmetabolic lrate land lwill lnot lallow lantigen-antibody lreactions lto loccur. l- l l l lcorrect lanswer.False The ltwo lintrinsic ldefense lsystems lhave lmany lcomponents. lWhich lof lthe lfollowing lcell ltypes lis lnot la lcontributor lto lspecific limmunity a. lnatural lkiller lcells b. lplasma lcells c. lt-cells d. lb-cells l- l l l lcorrect lanswer.a. lnatural lkiller lcells Which lof lthe lfollowing lis lnot la lsign lof linflammation? a. lredness b. lfever c. lswelling d. lpain l- l l l lcorrect lanswer.b. lfever Most lpathogens lthat ltry lto lenter lyour lbody a. lare lstopped lby lsurface lbarriers b. lare lkilled lby lthe lhumoral limmune lresponse c. lcause linflammation d. lare lkilled lby lantimicrobial lproteins, lphagocytes, land lother lcells l- l l l lcorrect lanswer.a. lare lstopped lby lsurface lbarriers Saliva land llacrimal lfluids lcontain lthis lenzyme lthat ldestroys lbacteria. a. lSalivase b. lTrypsin c. lAmylase d. lLysozome l- l l l lcorrect lanswer.d. lLysozome Intrapleural lpressure lis lalways l a. lhigher lthan latmospheric b. lhigher lthan lintrapulmonary c. lnegative d. lA land lC l- l l l lcorrect lanswer.c. lnegative Which lof lthe lfollowing lis lnot lan levent lnecessary lto lsupply lthe lbody lwith lO2and ldispose lof lCO2? a. lexternal lrespiration b. linternal lrespiration c. lblood lpH ladjustment d. lpulmonary lventilation l- l l l lcorrect lanswer.c. lblood lpH ladjustment __ lare lsubstances lthat lcan ltrigger lthe ladaptive ldefense land lprovoke lan limmune lresponse. a. linterleukins b. lantibodies c. lhaptens d. lantigens l- l l l lcorrect lanswer.d. lantigens Which lof lthe lfollowing lare lfunctions lof lthe llarynx? a. lspeech lproduction b. lairway c. lswitching lmechanism d. lall lof lthese l- l l l lcorrect lanswer.d. lall lof lthese When lT-cells lmature, lnegative lselection: a. leliminates lcells lthat lare lstrongly lanti-self b. leliminates lcells lthat lare lself-tolerant c. leliminates lcells lthat lshould lhave lstayed lin lbone lmarrow d. leliminates lcells lthat lsecrete lantibodies l- l l l lcorrect lanswer.a. leliminates lcells lthat lare lstrongly lanti-self The lonly lT-cells lthat lcan ldirectly lattack land lkill lother lcells lare__________. a. lregulatory lcells b. lcytotoxic lcells c. lplasma lcells d. lhelper lcells l- l l l lcorrect lanswer.b. lcytotoxic lcells The lcell-mediated limmune lresponse lis limportant lbecause lantibodies: a. lcannot lrecognize lcells linfected lwith lviruses b. lcannot lrecognize lviruses c. lare lproduced lvery lslowly d. lonly lwork lonce l- l l l lcorrect lanswer.a. lcannot lrecognize lcells linfected lwith lviruses Which lof lthe lfollowing lis la lcharacteristic lof la lsecondary limmune lresponse? a. la lsecondary limmune lresponse lproduces lfewer lantibodies lthan la lprimary limmune lresponse b. la lsecondary limmune lresponse lis lstarted lby lnaive llymphocytes lwhile la lprimary limmune lresponse lis lstarted lby lmemory lcells c. la lsecondary limmune lresponse ldoes lnot llast las llong las la lprimary limmune lresponse d. la lsecondary limmune lresponse lis lfaster lthan la lprimary limmune lresponse l- l l l lcorrect lanswer.d. la lsecondary limmune lresponse lis lfaster lthan la lprimary limmune lresponse During lnormal linspiration a. lintrapolmonary lvolume lincreases b. lthe ldiaphram lis lrelaxed c. lintrapolmonary lpressure lincreases d. lintrapolmonary lvolume ldecreases l- l l l lcorrect lanswer.a. lintrapolmonary lvolume lincreases Which lof lthe lfollowing lis lnot la lcharacteristic lof lthe linflammatory lresponse? a. lprevents lthe lspread lof lthe linjurious lagent lto lnearby ltissue b. lreplaces linjured ltissues lwith lconnective ltissue c. lsets lthe lstage lfor lrepair lprocesses d. ldisposes lof lcellular ldebris land lpathogens l- l l l lcorrect lanswer.b. lreplaces linjured ltissues lwith lconnective ltissue Which lof lthe lfollowing lis lnot ltrue labout lantibodies? a. lthey lhave lcomplement lbinding lsites b. lthey ldirectly ldestroy lpathogens c. lthey lneutralize lpathoens d. lthey lcause lagglutination l- l l l lcorrect lanswer.b. lthey ldirectly ldestroy lpathogens One lreason lwe lcan lhold lour lbreath lfor la llong ltime lis: a. lexcess lcarbon ldioxide lcan lbe lconverted lto lbicarbonate land lexcreted lby lthe lkidneys b. lhemoglobin lcan lbe lsaturated lin l.25 lseconds c. lhemoglobin lunloads lonly labout l25% lof lits loxygen lin l1 ltrip lthrough lthe lsystemic lcirculation d. lour lbody lcan lresist lchanges lin lblood lpH l- l l l lcorrect lanswer.c. lhemoglobin lunloads lonly labout l25% lof lits loxygen lin l1 ltrip lthrough lthe lsystemic lcirculation When lphagocytes lleave lthe lcapillary lwall lit lis lcalled l a. ldiapedesis l b. lleukocytosis c. lchemotaxis d. lmargination l- l l l lcorrect lanswer.a. ldiapedesis Surfactant lhelps lto lprevent lthe lalveoli lfrom lcollapsing lby a. linterfering lwith lthe lcohesiveness lof lwater lmolecules, lthereby lreducing lthe lsurface ltension lof lalveolar lfluid b. lhumidifying lthe lair lbefore lit lenters c. lwarming lthe lair lbefore lit lenters d. lprotecting lthe lsurface lof lalveoli lfrom ldehydration land lother lenvironmental lvariations l- l l l lcorrect lanswer.a. linterfering lwith lthe lcohesiveness lof lwater lmolecules, lthereby lreducing lthe lsurface ltension lof lalveolar lfluid Which lof lthe lfollowing lare ltrue labout lnatural lkiller lcells? a. lall lof lthese b. lthey lare lnonspecific c. lthey lenhance lthe linflammatory lresponse d. lthey lrelease lperforins l- l l l lcorrect lanswer.a. lall lof lthese What lpercent lof lcarbon ldioxide lis lcarried lby lhemoglobin lin lthe lblood? a. l20 b. l10 c. l97 d. l70 l- l l l lcorrect lanswer.a. l20 Air lmoves linto lthe llungs lbecause: a. lthe lgas lpressure lin lthe llungs lbecomes llower lthat lthe loutside lpressure las lthe ldiaphragm lcontracts b. lthe lvolume lof lthe llungs ldecreases lwith linspiration c. lcontraction lof lthe ldiaphragm ldecreases lthe lvolume lof lthe lpleural lcavity d. lthe linternal lintercostal lmuscles ldecrease lthe lthoracic lcavity lvolume l- l l l lcorrect lanswer.a. lthe lgas lpressure lin lthe llungs lbecomes llower lthat lthe loutside lpressure las lthe ldiaphragm lcontracts Which lof lthe lfollowing lis lassociated lwith lpassive limmunity? a. lbooster lshot b. linfusion lof lweakened lviruses c. lpassage lof lantibodies lfrom la lpregnant lmother lto lher lfetus d. llong-term limmune lprotection l- l l l lcorrect lanswer.c. lpassage lof lantibodies lfrom la lpregnant lmother lto lher lfetus Which lof lthe lfollowing lwould lincrease lhemoglobin's laffinity lfor loxygen? a. ldecreased ltemperature b. lincreased ltemperature c. lincreased lBPG lconcentration d. ldecreased lpH l- l l l lcorrect lanswer.a. ldecreased ltemperature When la llocalized larea lexhibits lincreased lcapillary lfiltration, lhyperemia, land lswelling lit lis lan lindication lthat: a. lantigens lare lpresent b. lfever lis ldeveloping c. lan limmune lresponse lis lunderway d. linflammation lis loccurring l- l l l lcorrect lanswer.d. linflammation lis loccurring Which lof lthe lfollowing lis lnot ltrue labout lmonoclonal lantibodies? a. lthey lare lused lin lresearch land lclinical ltesting b. lthey lhelp lprovide lactive limmunity c. lthey lbind lto la lsingle lantigenic ldeterminant d. lthey lare lproduced lby lhybridoma lcells l- l l l lcorrect lanswer.b. lthey lhelp lprovide lactive limmunity The lrelationship lbetween lthe lpressure land lvolume lof lgases lis lgiven lby l__________. a. lCharles' llaw b. lHenry's llaw c. lDalton's llaw d. lBoyle's llaw l- l l l lcorrect lanswer.d. lBoyle's llaw Which lnonspecific ldefense lcells lspecialize lin lattacking lcancer lcells land lvirus-infected lcells? a. lnatural lkiller lcells b. lbasophils c. lmacrophages d. lall lof lthese l- l l l lcorrect lanswer.a. lnatural lkiller lcells the lPO2 lof lblood lin llung lcapillaries lreaches lequilibrium lwith lthe lPO2 lof lthe lalveoli lrapidly lbecause a. lthe lcapillary lwalls lare lless lthan l1 lmicrometer lthick b. lthere lis la lsteep lpressure lgradient c. lblood lvelocity lis llower lin lcapillaries d. lall lof lthese l- l l l lcorrect lanswer.d. lall lof lthese The ltotal lsurface larea lof lthe lrespiratory lmembrane lis l a. lless lthan lthe lskin b. labout lthe lsame las lthe lskin c. ltwice las lbig las lthe lskin d. l40 ltimes llarger lthan lthe lskin l- l l l lcorrect lanswer.d. l40 ltimes llarger lthan lthe lskin Functions lof lthe lspleen linclude lall lof lthose lbelow lexcept l___________. a. lstorage lof lblood lplatelets. b. lcrypts lthat ltrap lbacteria c. lstorage lof liron d. lremoval lof lold lor ldefective lblood lcells lfrom lthe lblood l- l l l lcorrect lanswer.b. lcrypts lthat ltrap lbacteria Select lthe lcorrect lstatement labout llymph ltransport. a. lunder lnormal lconditions, llymph lvessels lare lvery lhigh-pressure lconduits b. llymph ltransport lis lonly lnecessary lwhen lillness lcauses ltissue lswelling c. llymph ltransport lis lfaster lthan lthat loccurring lin lveins d. llymph ltransport ldepends lon lthe lmovement lof ladjacent ltissues, lsuch las lskeletal lmuscles l- l l l lcorrect lanswer.d. llymph ltransport ldepends lon lthe lmovement lof ladjacent ltissues, lsuch las lskeletal lmuscles Select lthe lcorrect lstatement labout llymphocytes a. lB lcells lproduce lplasma lcells, lwhich lsecrete lantibodies linto lthe lblood b. lthe ltwo lmain ltypes lare lTcells land lmacrophages c. lT lcells lare lthe lprecursors lof lB lcells d. lT lcells lare lthe lonly lform lof llymphocyte lfound lin llymphoid ltissue l- l l l lcorrect lanswer.a. lB lcells lproduce lplasma lcells, lwhich lsecrete lantibodies linto lthe lblood Select lthe lcorrect lstatement labout llymphoid ltissue a. lT llymphocytes lact lby lingesting lforeign lsubstances b. lonce la llymphocyte lenters lthe llymphoid ltissue, lit lresides lthere lpermanently c. llymphoid ltissue lis lpredominantly lreticular lconnective ltissue d. llymphoid lmacrophages lsecrete lantibodies linto lthe lblood l- l l l lcorrect lanswer.c. llymphoid ltissue lis lpredominantly lreticular lconnective ltissue Function lof lthe llymphatic lsystem linclude l_____. a. ltransport lof lexcess ltissue lfluid lto lthe lblood lvascular lsystem b. ltransport lof lred lblood lcells lto lthe lblood lvascular lsystem c. lexcretion lof lexcess ldietary lfat d. lmaintenance lof lblood lpressure lin lthe lvenous lcirculation l- l l l lcorrect lanswer.a. ltransport lof lexcess ltissue lfluid lto lthe lblood lvascular lsystem Which lof lthe lfollowing lis lnot ltrue lof lsaliva? a. lmoistens lfood land laids lin lcompacting lof lthe lbolus b. lcontains lenzymes lthat lbegin lthe lbreakdown lof lproteins c. ldissolves lfood lchemicals lso lthey lcan lbe ltested d. lcleanses lthe lmouth l- l l l lcorrect lanswer.b. lcontains lenzymes lthat lbegin lthe lbreakdown lof lproteins You lhave ljust leaten lfrench lfries, lbuttered ltoast, lice lcream, land lwhole lmilk. lWhich lof lthe lfollowing lglands lwould lbe lactive lin lhelping lyou lto ldigest lthis lfood? a. lthe lthyroid lgland b. lthe lbuccal lgland c. lthe lparotid lgland d. lthe lpancreas l- l l l lcorrect lanswer.d. lthe lpancreas Which lof lthe lfollowing lis lnot la lfunction lof lthe lsmall lintestine a. labsorption l b. lingestion c. lchemical ldigestion d. lmechanical ldigestion l- l l l lcorrect lanswer.b. lingestion Chemical ldigestion lstarts lin lthe a. lmouth b. lstomach c. lsmall lintestine d. lpancreas l- l l l lcorrect lanswer.a. lmouth Bacteria lliving lin lthe lcolon l a. lferment lindigestible lcarbohydrates b. lsynthesize lvitamins c. lrelease lirritating lgases l d. lall lof lthese l- l l l lcorrect lanswer.d. lall lof lthese All lof lthe lfollowing lwould lstimulate lpancreatic lsecretion lexcept: a. lCCK b. lsecretin c. lparasympathetic lstimulation d. lserotonin l- l l l lcorrect lanswer.d. lserotonin The lstomach lproduces lenzymes lwhich lwill lbreak ldown: a. lproteins b. lcarbohydrates c. llipids d. lall lof lthese l- l l l lcorrect lanswer.a. lproteins The lliver lproduces lchemicals lwhich lwill lhelp lbreak ldown l: a. lproteins b. lcarbohydrates c. llipids d. lall lof lthese l- l l l lcorrect lanswer.c. llipids Cholesterol, lwhile lit lis lnot lan lenergy lmolecule, lhas limportance lin lthe lbody lbecause l________. a. lit lenters lthe lglycolytic lpathway lwithout lbeing laltered b. lit lis la lstabilizing lcomponent lof lthe lplasma lmembranes land lis lthe lprecursor lof lsteroid lhormones c. lit lhelps lprovide lessential lnutrients lto lthe lbrain land llungs d. lit lhelps lmobilize lfats lduring lperiods lof lstarvation l- l l l lcorrect lanswer.b. lit lis la lstabilizing lcomponent lof lthe lplasma lmembranes land lis lthe lprecursor lof lsteroid lhormones