Biosc&0150:&Foundations&of&Biology&I.& & Review&13:&Chapter&47&49& &Adel,&Anthony,&Megan,&Dr.&Swigonova& & Page&1&of&6&Review&Chapter&47:&Chemical&signals&in&animals&&1. Compare&and&contrast&neural&signals&to&endocrine&signals.&Neural& signals& are& spread& electrically& by& neurons,& whereas& endocrine& signals& can& be& sent& by&specialized&cells&that&secrete&hormones,&or&neuro ns&that&release&h orm one s&into&the&b loodstream &in&the& case& of& neuroend oc rine& signals.& & Neural& signals& can& be& sent& very& quickly& because& they& are&electrical&in&nature&but&they&only&release&a&small&amount&of&shortElive d&neu ro tr an s m it te r&at&a&time&into&the&s y na p s e.&&E n d o crin e &s ign a ls&a re &slo wer&than&n e u ral&s ig n als &b u t&ca n &re le as e &a&la rg er &amount&of&hormones&at&a&time&compared&to&the&small&amount&of&neurotransmitter&released&in&neural&signals.&&&2. Explain&why&chemical&hormones&can&have&large&effects&on&all&of&their&target&cells&even&when&they&are&in&small&q u a n titie s .&Th e n ,&ex p la in&why&action &p o te n tia ls &ca n n ot &af fec t&a &wide&range&of&cells&via&electrical&signals.&&Chemical&h o rmones&c a n &tra v e l&throughout&the&b o d y &within&the &b lo od&stream.&When&hormones&bind&or&move&into&cells&with&specific&receptors&for&them,&a&signal&transduction&cascade&occurs,&giving&a&large&cell&response.&On&the&other&hand,&an&action&potential&can&only&have&a&short&term&effect&on&a&small&number&of&cells&because&the&electrical&signal&cannot&travel&throughout&the&body.&&3. How&do&hormones&travel&throughout&the&body?&Through&the&bloodstream&a. When&a&hormone&is&released,&why&are&only&certain&cells&affected?&The&response&to&a&hormone&is&tissue&specific&because&only&certain&cells&contain&receptors&for&particular&hormones&b. Do&steroid&hormones&produce&new&proteins&or&activate&existing&ones?&What&about&nonEsteroid&hormones?&Steroid&hormones&activate&transcription&factors&that&lead&to&the&production&of&new&proteins;&nonEsteroid&hormones&trigger&signal&transduction&cascades&that&activate&existing&proteins&c. Compare&and&contrast&the&modes&of&action&of&steroid&vs.&nonEsteroid&hormones.&Steroid&hormones&act&directly&and&alter&gene&expression.&They&bind&to&receptors&inside&the&cell,&forming&a&co m p lex&tha t&bin ds&to &DN A &an d&ac tivate s&tran scrip tion .&No nEsteroid&hormo nes&act&indirectly,&a n d &ac tiv a te &pr o te ins .&T h ey &b in d &to &re ce p to rs &o n&the&cell&surface&and&trigger&production&of&a&second&messenger&or&a&phosphorylation&cascade,&ending&in&activation&of&proteins&already&present&in&the&cell&d. Suppose&a&steroid&hormone&bound&to&a&cellEsurface&receptor.&Explain&how&its&mode&of&action&would&compare&to&a&polypeptide&hormone.&The&steroidEhormone&complex&would&probably&fail&to&bind&to&the&ho rm o neErespons e&element.&If&so,&then&gene &exp ressio n&w o uld &not&change—the&arrival&of&the&horm on e&w ou ld&h ave &little&to&no&effe ct&on &the&ta rget&ce ll.&The&mode&of&action&would&be&similar—hormone&binding&would&have&to&trigger&a&signal&transduction &even t&tha t&resu lted&in&p rod uctio n&o f&a&seco nd &m esse ng er&or&a &pho sp ho rylation &cascade&&4. Consider&three&of&the&six&categories&of&chemical&signals&in&animals:&autocrine,&paracrine,&and&endocrine.&In&terms&of&prefixes,&decide&how&each&of&these&systems&operates&with&regards&to&spacing&in&the&bo d y.& Auto&E&the &s ignal&from &a &ce ll&a c ts&on&the&ce ll&itself;&para&E&th e &s ig n a l&from&a&cell&a c ts &o n &cells&besides&it&(think&“para”llel);&endo&E&the&sign a l&f ro m&a&cell&is&tra n s p o r te d &“ w it h in ” &th e &b ody&to&other&cells&through&the&bloodstream.&&Biosc&0150:&Foundations&of&Biology&I.& & Review&13:&Chapter&47&49& &Adel,&Anthony,&Megan,&Dr.&Swigonova& & Page&2&of&6&5. In&the&n eu r o e n d o cr in eE to Eendocrine&pathway,&there&are&two&chances&for&feedback&inhibition&to&occur,&whereas&the&endocrine&and&neuroendocrine&pathways&only&have&one&chance&for&feedback&inhibition &t o&o c cu r.&F irs t,&e xp la in &w h a t&th e &p ro ce s s&o f&fe e d b ac k&in h ib itio n &is .&Th e n ,&d ec id e&why&the&neuroendocrineEtoEendocrine&pathway&has&two&chances&for&feedback&inhibition&to&occur.&&Feedback&inhibition &o c cu rs &w h e n &th e&p r od u c t&o f&a &p ro ce ss &in h ib its &its&o wn&produ ct io n &(similar&to&LeC h a tlie r’s&Principle).&The&neuroendocrineEtoEendocrine&pathway&has&two&chances&for&feedback&inhibition&because&it&takes&two&secreted&produ cts&to&elicit&a&resp on se &in&target&ce lls.&First&com es&th e&neuroendocrine&signal,&which&in&turn&stimulates&and&endocrine&gland&that&secretes&an&endocrine&signal.&Both&of&these&products&can&inhibit&their&own&production&&6. You&have&identified&a&certain&hormone&which&directly&travels&into&its&target&cells.&Is&this&hormone&water&or&lipid&soluble?&What&class&of&macromolecule&is&this&hormone&likely&to&be?&&Lipid&solu b le ;&steroid&hormone&Would&you&expect&a&polar&polypeptide&hormone&to&bind&to&a&receptor&or&diffuse&into&a&cell?&Bind&to&a&receptor&7. Why&is&the&pituitary&gland&considered&the&“master&gland”?&The&pituitary&gland&is&a&important &in &responding &to&the &env iron m en t&usu ally&w ith ou t&our&kn o w ledg e.&It&acts&as&a&th erm o sta t&that&co ntro ls&all&other&glands&that&are&responsible&for&hormone&secretion.&It&controls&hormone&functions&such&as&our&temperature,&thyroid&activity,&growth,&urine&production,&and&testo stero n e&pro du ctio n&in&m a les&and&ovulation&and&estrogen&production&in&females.&&a. Suppose&you&were&to&inject&someone&with&adrenocorticotropic&hormone&(ACTH).&What&effect&would&this&have&on&cortisol&levels&in&the&body&and&why?&Cortisol&is&a&glucocorticoid &that&suppresse s&AC TH &pro du ction &an d&th is&is&possible &bec aus e&co rtisol&prev en ts&the &release &of&corticotropinEreleasing&hormon e&(C RH ),&wh ich &stim ula tes&the &an terior&p ituitary &glan d&to&secrete&ACTH.&&b. Why&is&this&a&form&of&feedback&inhibition?&When&CRH&is&released&from&the&hypothalamus&into&the&a n te rio r&p it uit ar y&g la nd ,&t his &st imulates&th e&r ele a se &o f&A C T H ,&h o w e ve r,&if&th e re &is&t o o&much&ACTH,&cortisol&will&be&released&back&towards&the&hypothalamus&to&suppress&CRH&and&to&the&anterior&pituita ry&glan d&to&su pp res s&AC TH ’s&relea se.& &c. Suppose&a&person’s&ACTH&levels&are&high&and&you&inject&the&person&with&cortisol;&however,&this&person’s&bod y&is&damaged&and&is&un ab le&to&reg ulate &the&h orm o ne s&thro ug h&fee