[Advanced Exercise Physiology] Katarina Borer - Advanced Exercise Endocrinology (2013, Human Kinetics)

Universit y of Michiga n Hu m a n Ki neti cs Katarina T . Borer , Ph D A DV A N CED EX ER CISE E ND OC R I NOLO G Y Librar y of Congr es s Cata log ing-i n-P ublic ation Dat a Borer, Kata r i na T . Adv anc ed exercise endoc r inology / Kat a r i na T . Bore r . p. ; cm. -- ( Adv anc ed exercise physi olo gy ser ies ) Includes bibliograph ica l references a nd index. I. Title. II. Ser ies: Ad vance d ex ercise physio logy ser ies. [ D N L M : 1. E ndo c r i n e Syst e m- -p hysiolog y . 2. P hysic a l E xer t io n- - phys iolog y . W K 10 2] 61 2 . 4 - - d c 2 3 20 1 203 1 085 I S B N - 1 0 : 0- 7 3 60- 7 5 1 6- X ( pri n t ) I S B N - 1 3 : 9 7 8-0- 7 3 6 0- 7 5 1 6- 9 (p ri n t ) Copyr ight © 20 13 b y Kat a r ina T . Borer Al l r ights re ser ved. Except for use in a r eview , the re product ion or uti li zat ion of this work in a ny form or by any elect ron ic, mecha nica l, or ot her me an s, now known or here af te r inven te d, i ncluding xerography , phot ocopyi ng, and re cord ing, and i n a ny in format ion storage a nd ret r iev al system, is forbidden without the w r itt en per m ission of the publi sher . Acqui sit ion s E d itor: Amy N. T occo; Developmental E ditor: A ma nda S. Ewing; A ss i st a nt E d ito r s: Ka l i Cox, Derek Ca mpbel l, Susan D. Huls, a nd Casey A. G entis; Cop yedito r: A ma nda M. E ast in - A lle n; Proofre ader: Red I nc. ; Indexer: And r ea J. Hepner; Permi s sion s Ma nager: D alene Re eder; Graph ic D e sig ner s: Joe Buck and Fre d Sta rbi rd; Graph ic Ar tis t: T a ra W elsch; Cov er De sig ner: Rober t Reuther; P hoto P roduct ion Ma nager: Jason A l len; Ar t Ma n ager: Kel ly Hendren; As sociate Art Manager: Ala n L . 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Bo x 80 T or rens Pa rk , South Austr a lia 50 62 080 0 222 0 62 e-ma i l: in fo @hk newzea la nd.com E 4 517 iii Conte n t s Pref a c e v S eries Preface vi i Chapter 1 Unique Properties of Endocrine and Autonomic Messengers . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Func t ions o f the E ndoc rin e S ys tem an d Au tonom ic Ner vou s Sys tem . . . . . . . . . . . . . . . . . . . . . 2 Clas sific at ion of Hormones . . . . . . . . . . . . . . . . . 5 Chemical Structure of Hormo nes . . . . . . . . . . . . . . . 6 H ormone Release and T ranspor t . . . . . . . . . . . . . . . 15 Hormon e Rec eptor s and H ormon e \u2013 Re cep tor Mes s age T ran sduc tion . . . . . . . . . . . . . . . . . . . . . . 1 8 Proper t ies of Hormone \u2013 Rec eptor Interac tions . . . . . . . . . 26 Sum mar y . . . . . . . . . . . . . . . . . . . . . . . 29 Chapter 2 A ctivation of No nhormonal Si gnaling Du ring E x ercise . . . . . 31 Sign al T r an sdu ct ion by N eur ona l and El ec tr os t at ic Eve nt s in E xercis e . . . . . . . . . . . . . . . . . . . . . . . 32 Intr ac ellu lar C al cium Rel ea se a s a T r ig ger of S igna l T ran sduc tion . . . . . . . . . . . . . . . . . . . . . 33 Sign al T r an sdu ct ion o f Me cha nic al S tr a in, V ibr at ion, and F luid Sh ea r . . . . . . . . . . . . . . . . . . . . 36 Sign alin g in Resp ons e to Se nsing E ner gy N ee d . . . . . . . . 44 Fre e Rad ic als a s Ini ti ator s o f Me ss ag e T r ans duc ti on . . . . . . 46 Sum mar y . . . . . . . . . . . . . . . . . . . . . . . 53 Chapter 3 A utonomic and Hormonal C on trol of the Ca rdiore spirator y S ystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Af fer ent S igna ls to t he A NS . . . . . . . . . . . . . . . . 56 Inte gr ati ve Br a in Circ uit s an d Ef fe ren t Co mpone nt s of A NS Re fl exes . . . . . . . . . . . . . . . . . . . . 58 C ontrol of Car diorespira tor y Func tion by ANS and Hormones . . . 69 Sum mar y . . . . . . . . . . . . . . . . . . . . . . . 77 Chapter 4 Body Fluid Ba lance . . . . . . . . . . . . . . . . . . . . . . . 79 Incr ea se s in Bo dy H ea t Lo ad Duri ng E xer cis e . . . . . . . . . 80 Th ermo re gula tor y Cha nge s in Bo dy Wa ter Dur ing E xe rci se . . . . 80 Con sequ enc es o f Flui d Los s T hroug h Swe a ting . . . . . . . . 83 Ce ss at ion o f Rena l Rea bsor pt iv e Func t ion Dur ing E xer ci se . . . . .87 Thir s t an d Na Hun ger Af te r E xer cis e . . . . . . . . . . . . . 90 H yperhydr ation and H yponat remia . . . . . . . . . . . . . . 91 St r ate gie s for F luid M ana geme nt in E xerc ise . . . . . . . . . 92 Sum mar y . . . . . . . . . . . . . . . . . . . . . . . 95 iv Contents Chapter 5 Hormones and Fuel Use in Ex ercise . . . . . . . . . . . . . . . 97 Horm ona l Med ia tion o f Ener g y Ba la nc e . . . . . . . . . . . . 97 Horm one s in Fue l Mobil iz at ion a nd U tili z at ion Dur ing Aerob ic E xerci se . . . . . . . . . . . . . . . . . . . 10 9 Horm one s in Fue l Mobil iz at ion a nd U tili z at ion Dur ing An aer obi c E xerc is e or RE . . . . . . . . . . . . . . . . 118 Summar y . . . . . . . . . . . . . . . . . . . . . . . 12 4 Chapter 6 H ormonal Control of Energy E xpenditure and In take . . . . . 12 7 Energ y-Regul atin g Mech anism . . . . . . . . . . . . . . . 12 8 Des cr ipto rs a nd C ont rol s of F ee ding B eha vior . . . . . . . . . 13 4 Role of P hy sic al A c ti vi t y in th e Regul at ion o f Bod y M as s . . . . 13 7 Regul at ion of B od y Ma s s Thr ough H omeo st a ti c Versu s Nonhomeostatic Controls . . . . . . . . . . . . . . . . 13 9 Bod y M as s Regul at or y M ec han ism Ver sus Ob esi t y and Weig ht Loss . . . . . . . . . . . . . . . . . . . 14 5 Summar y . . . . . . . . . . . . . . . . . . . . . . . 14 8 Chapter 7 E xercise and Rep roduct ive Hormones . . . . . . . . . . . . 14 9 Development of Phenot ypic Sex ual Dimorphism . . . . . . . . 14 9 Ef fe c ts o f E xer cis e on S ex Hor mone S ec re tio n . . . . . . . . . 1 61 Ef fe c ts o f Se x Horm one s on Phy sic a l Per for man ce . . . . . . . 17 0 Summar y . . . . . . . . . . . . . . . . . . . . . . . 174 Chapter 8 Hormonal Medi ation in T raini ng Adaptations . . . . . . . . . 17 7 Sy s temi c Horm one s in Ad apt a tio ns to En dura nc e T r aini ng . . . . 17 8 Role of S y st emic A n abol ic Hor mon es in A dap t at ions to Resistance T raining . . . . . . . . . . . . . . . . . 1 84 Nutri tional Modula tion of Hormonal Adap ta tions to E xer cis e T r ain ing . . . . . . . . . . . . . . . . . . 19 2 Summar y . . . . . . . . . . . . . . . . . . . . . . . 19 9 Chapter 9 E xercise and Endocri ne Rh ythm s . . . . . . . . . . . . . . . 2 01 Basi cs of Biologic al Rhy thm Phy siology and T er minology . . . . 2 01 Sy nc hroni z at ion o f Circ adi an Rh y t hms by t he Suprachiasmatic Nucleus . . . . . . . . . . . . . . . . 20 5 Con tr ol of Bi olo gic al Rh y t hms by t he F oo d-En tr a inab le Oscil lator . . . . . . . . . . . . . . . . . . . . . . 20 9 Con tr ol of Ul tr adi an Rh y t hms . . . . . . . . . . . . . . . 20 9 Con tr ol of Bi olo gic al Rh y t hms by E xerc is e . . . . . . . . . . 2 11 Summar y . . . . . . . . . . . . . . . . . . . . . . . 2 18 Chapter 1 0 Measurin g Hormones . . . . . . . . . . . . . . . . . . . . . 2 19 Mea suring Hormone Concen tra tion . . . . . . . . . . . . . 2 19 Mea suring Biologica l Act ions of Hormones . . . . . . . . . . 2 24 Me asur ing H ormo ne S yn th esi s and Si te o f Pro duc ti on . . . . . 2 25 Me asur ing t he R ate o f Hor mone S ec re tio n . . . . . . . . . . 2 25 Summar y . . . . . . . . . . . . . . . . . . . . . . . 2 28 Refer en c e s 229 Ind ex 2 57 Ab ou t th e Au th or 2 64 v P r e f ac e I ndividuals in dev el oped so cieties are i ncrea singly p lagued by healt h probl ems that a re inextr icabl y rooted i n hor monal abnor ma lities. Excess iv e food int a ke and relativ e inact ivi ty lead to i nsul in resista nce a nd ty pe 2 d iabetes ( T2D ) , a condition associated with metab olic and endocr ine abnor ma l ities that a re collectiv el y descr ibed a s metabolic syndrome. In met abolic syndr ome, many tissues that a re essentia l f or metabol ism become resistant to t he ad ipocyte hor mone leptin a s w ell as to i nsuli n. T he stress of contempora r y li fe also increa ses sec retion of cortisol to lev els that a dv ersel y af fect mental we ll-being, musc le and bone integ r ity , im mune f unct ion, and metabolism. A ma zi ngly , mos t of these metabol ic and endocr i ne abnorma l ities can be p rev ented and ev en resol v ed t h rough incre ase d phy si cal act ivi ty , i ndicati ng that hor mone secret ion and action ar e fu nctional ly lin ked to ex ercise and a re nec essar y f or the m ai ntenanc e of health. The c onnect ion between e xercise, h or mones, and hea lth has be en stud ied and ack now l- edged for se v eral de cades. Ho w ev er , t he f iel d of kinesiol ogy to date ha s not suff icien tly engag ed in expl ori ng and exp lo i ti ng th is conne ction. Although medica l science acknow l edges the i mpor t ance of ex ercise in prev enting morbidi ties and i n resol ving ma ny health conditions, it s ti ll relies more heavily on medications and su rgery t han on exercise prescription and lacks suff icient understa ndi ng o f ex ercise. Ki nesi ol ogists, e xper ts on a ll m att ers regard ing phy si cal act ivi ty , rem ai n ina dequat el y e xposed to endocr i nol ogy despite the recent add ition of chap ters on hor mones to ex ercise ph y si ol ogy textbooks. Courses i n ex ercise endocr inolo gy a re not promi nently o ffered or t aught in most e x ercise science cur r icula. It is my fir m b elief that t h is neglect or disinterest in exercise endocr inolo gy is a tempor a r y condition that is caus - ing a loss o f resea rch oppor t un ities, w h ich a ne w g eneration of ki nesi ol ogists wil l cor rect . My o w n inv ol v emen t in ex ercise endocr i nol ogy sta r ted w ith an a ccidental d iscov ery i n the m id- 1 970s of a stri k i ng endocri ne effect of ph y sical activity . Th is changed t he cour se of m y resea rch and profess ional car eer a nd tu r ned me i nto an exercise end ocr i nol ogist. M y core interest i n energy regu lation led me to pi t v ol unta r y exercise ag ai nst palat able f ood to see how ani ma ls presente d with these t wo opti ons w ould ma inta i n body wei ght. The u nex - pect ed d iscov er y t hat mat u re ha msters provided with a r u nn i ng whee l sho w ed a d ra matic incre ase in skeletal a nd somatic growt h led me to measu re t heir g rowth hor mone ( GH ), dev e lop and v al idate r adioim munoassay (R I A ) specif ic to GH in t his sp ecies, and t r y to underst and why e x ercise appea re d to rev erse the slo w growth i n t he matu re st age o f li fe to the rapid gr o wt h that is cha ra cter istic of imm atu re a n im als. I hav e pursued t he conne ction between phy si cal a ctivity , hormones, a nd huma n phy si ol ogy e ver s ince. I soon rea liz ed t hat to tell t he story ab out ho w hormones and phy si cal a ctivi ty i nteract one has to go bey ond presenting hormone act ions or gan ize d by their sou rce of or igin, a conv enti on that is use d in most endocr inolo gy textbooks a nd in most chapters on ex ercise phy si ol ogy . Al l hor mones ha v e pl eiotropic actions\u2014a nabolic, catabolic, metabolic, or im mune \u2014 t hat di ffer b y the t issue in which they act and by ty pe of ph ysi cal act ivi ty . W hen I contemplated presenting a n integr ativ e account of the i nteraction of hormones and ex ercise, f ew te xts on hormones a nd phy si cal act ivi ty existed . Some o f them were v ery old, a nd some w ere edited collections of poorl y integrat ed chapters. G eneral ly missing was an ac curat e view o f ho w vi Preface acute phy si cal act ivi ty a ffects hor mone sec retion and ho w such endocri ne action af fects adapt ations to habitua l ex ercise . My fir st attempt to present t his stor y took 1 0 y ea rs a nd resulted i n Exercise E nd ocri nology , pu blished by H uma n K i netics in 20 03. Science has changed a gre at dea l since 20 03 . Endocr i nol ogy and ex ercise phy si ol ogy hav e b ecome more molecular, and a gr eat dea l more k no w ledge has accumulat ed about hormones a nd ex ercise. B ecause a good te acher and w r iter inter prets a nd organ iz es new k no w ledge, I accepted t he chal leng e of writi ng Advance d Exercise E nd ocri nology . Format requ irements i n th is ser ies made Adva nce d Exercise E nd ocri nology more compact t ha n Exercise E nd ocri nology , bu t it remains h igh ly integrativ e and r ichly illustr ated. I nteract ions between phy si cal a ctivity and hor mones ar e presented f rom a more mol ecula r p erspe ctiv e rather t ha n a phenomeno lo gical p erspe ctiv e. Theref ore, students and ot her reader s seek ing more descr iptiv e inform ation about hormone secret ion and phy si ol ogy can revisi t Exercise Endocrinology . Chapter 1 of Advan ced Ex ercise En docr inol ogy intr oduces reader s to the essentia ls of hormone a nd autono m ic messen ger chemistr y , hor mone \u2013re ceptor i nteractions, and pr i ncipal tr ansduction pathwa ys. Chapter 2 focuses on elici tation of endocri ne signal ing a nd actions by m uscl e contract ions and phy si cal a ctivity without the need for hormona l inv o lv emen t or hormone \u2013 rec eptor bindi ng . Endocr ine a nd autonomic control of card ioresp ir ator y fu nction is presented i n chapter 3, w hich connect s the role of periphera l messaging d iscussed in chap - ter 2 with t he endocr ine c ontrol of hear t f unction by medulla r y a nd pontine br ai n centers. Chapters 4 a nd 5 d iscuss endocri ne inv ol v ement in f luid and f uel regulation, respect iv ely , dur i ng e x ercise. Chapter 6 dea ls with hor monal regu lation of ener gy ba lanc e th rough bra i n controls o v er inta ke a nd ex penditu re at rest a nd dur i ng e xercise . The role of reproductiv e hormones i n acute ex ercise and tr ai n ing adapt ations is discusse d in chapter 7 , a nd inv o lv e - ment o f other hor mones in t hese ad aptat ions is discussed in chapter 8. Because essentia l aspe cts of life-suppor ti ng processes such as H R, respi ration, hormone se cretion, and cel- lular g rowth a re rhyt h m ical a nd a re af fected by ex ercise, the role o f bi ol ogical rhyth ms i n hormone se cretion and ex ercise phy si ol ogy is the subject of c hapter 9 . I a m hoping reader s of th is text will be come energize d a nd intereste d in engaging in exercise end ocr i nol ogy resea rch. T o f acil itate t h is, chapter 1 0 d iscusses pr inciples o f hormone measu rements and wa y s to a v oid so me common pitfalls. One ex citing aspect of ex ercise endocr inolo gy is how i t connects m any sciences that study both hor mones a nd phy si cal a ctivity . An ex ercise endocr i nol ogist could e xp lore wa y s that phys ical activity inter acts with nutr ition to enha nce ex ercise per forma nce a nd tr ai n ing adapt ations or could focus on the eff ective ness of e x ercise in preven ting pe diat r ic obesi ty , met abolic dise ase i n m iddle age , or man i fes tat ions o f agi ng . I hope that rea ders of th is book , incl udi ng graduat e students, advanced u ndergra duates, and profess ionals in ma ny health f iel ds, wil l f ind resea rch ideas f or the st udy of unresolv ed questions on ho w i nteract ions between phy si cal act ivi ty a nd hor mone action can help maint ai n hea lth, improv e e xercise perform ance, a nd prev ent metabolic disabil ities. vii S er ie s P r e f ac e H aving a deta iled k now ledg e of the effects of e x ercise on speci f ic ph ys io lo gical sys tems a nd under var ious conditions is essential for adv ance d-le v e l ex ercise ph ys i - ol ogy students. For e xample, s tudents should be able to answ er questions s uch as these: What a re t he ch ronic effects of a sy stematic progra m of resis ta nce t ra in ing on ca rdiac str uct ure a nd f unction, vascular st r uctu re a nd f unction, and hemostat ic v ar iables ? How d o di fferent en viron ments in f luence the abil ity to ex ercise, and what can pushi ng the bo dy to its en viron menta l li m its tell us about ho w the bo dy funct ions duri ng e xercise ? When muscles a re inact iv e, w hat happens to t heir sensitivi ty to i nsul in, a nd what rol e do inact iv e muscles pla y in the dev el opment o f h yp eri nsul inem ia a nd ty pe 2 d iabetes ? These questions and ma ny others a r e answered in t he books i n Huma n K inet ics \u2019 Adv anc ed Exercise Ph ys io lo gy Ser ies. Beginn i ng where mo st intro ductory ex ercise phy si o lo gy textbooks end t heir d iscussi ons, each book in t h is ser ies descr ibes in det a il t he effects of e x ercise on a speci f ic ph ys io lo gical sys tem or the effects of externa l conditions on e xercise . Ar me d with t his i n f or mation, students wil l be b etter pr epa red bot h to conduct the h igh-qua lity r esea rch requ ire d for adv ancing scientif ic know ledg e and to ma ke de cisio ns in re al-life scena r ios suc h as the a ssessment of health a nd fitness or t he formulation of e ffectiv e e xercise guidelines a nd prescr iptions. Although ma ny graduat e progra ms a nd some undergra duate progra ms i n ex ercise science and k i nesio lo gy offer specif ic courses on a dv ance d topics in e xercise ph ys io lo gy , t here a re fe w g ood options for te xtbooks to suppor t t hose c lasses. Some instr uctors adopt genera l advanced phy si ol ogy textbooks, but suc h books focus al most entirely on ph y si ol ogy without em phas izin g exer cise physiolog y . Each book i n the Adv ance d Exercise Ph ysi o lo gy Ser ies add resses t he effects of e x ercise on a cer ta i n phy si ol ogical sy stem ( e. g. , card io v ascula r or neur omuscular ) or in cer t a in con- texts ( e. g. , i n var ious ty pes of en vi ronments ) . These textbooks a re i ntended pr i ma r ily f or students, but resea rchers and pr actitioners wil l also b enefit from the det a iled pr esentation of the most recent resea rch regard ing topics in e xercise ph ys io lo gy . This page intentionally left blank. 1 1 C H A P T E R Uni que Proper t ies of En docri ne and Aut onomic Mes senger s T he endocr ine system and the autonomic ner vous s ys tem ( ANS) are t he two mai n control sy stems that regulate a b ody\u2019 s inter na l environ ment and adjust ph y si ol ogical responses to ex ercise and ot her stressors. T he endocr i ne sy stem consists o f chemi- cal messengers released into ci rculat ion or into e xtracellula r a nd int racellula r f luids b y endocr ine gla nds (gla nds of inter na l sec retion ) a nd by endocri ne cells d ispersed t h rough ma ny body tissues and organs. The endoc r ine system uses circulat ion as a pri ncipal mode of dispersing its messeng ers, whereas t he A NS commun icates pr im a r ily th rough efferent neurons t hat t ran smit messages o f the cent ra l ner v ous sy stem ( CNS ) to ta rget or gans by wa y o f neurot ra nsm itters released i nto synaptic cl efts. T he A NS also uses the endoc r ine route of commun ication because its S neurot ra nsmitt ers, t he catecholam i nes, spill ov er into circu lation and act as hor mones. The a drena l cate cholam ine epineph r i ne (E) is a hor mone secr eted i nto circulat ion upon activ ation b y a sympathetic ( S ) ner v e. Many neurons secret e hormones i nto the blood and a re t heref ore define d as neu roendocr i ne cells. For insta nce, secr etion o f pituita r y hor mones is activ ated by neuroendoc r ine messengers rel ease d into hypotha la mo-hypophy sea l por ta l ci rculat ion b y h ypot ha lam ic neurons. T he f unctions of the endocr i ne system and the A NS a re int roduced together in t h is chapter because t hei r features r egardi ng secret ion and action a re sim ila r. 2 Advanced Exercise Endocrinology FUN C T IONS OF THE E N DO CR INE SYS T EM A ND AU T ONOM I C NERVOUS SY S T EM Homeostasis, the regu lation of the inter na l environ ment b y the endocr i ne sys tem a nd the A NS, en ta ils m ai ntenanc e of a s teady st ate of body f luids, ci rculation, bl ood pressu re, and a number of v a r iabl es in t he extracellula r f luids such as i onic and met abolite concentra- tions. The endocr i ne sys tem and t he A NS di rect ly inf luence energy bala nce by mo bili zi ng metabolic f uels ou t of storag e depots a nd controll ing fuel util izat ion and energy expendi- tu re. They also cont rol inta ke and upt a ke of n utr ients into cells and synt hesis o f fuel stores. Hormones a nd the A NS messeng ers a lso af fect body growth a nd t he body\u2019 s str uctu ra l and fu nctional di fferentiation b y orchestrati ng dev elopmen ta l changes and by facilitati ng adapt a - tions to metabolic a nd mechan ical cha llenges o f ex ercise. H or mones control reproductiv e fu nctions, which also can u ndergo c hanges in response to energ y dra i n and t he stre ss of some typ es of e xercise . Hormones a nd the A NS also respond to environ menta l and bioenergetic c hal lenges and states of emergenc y (inc luding ex ercise, f ood depr iv ation, e xposure to cold, injur y , and in fection ) when additional met abolic, card iorespirator y , a nd im mune responses a r e cal led f or . At s uch times, homeostat ic body fu nctions can b e o v er r uled to a ccom modat e operat ion of emerg ency body functions. For insta nce, dur ing ex ercise, aspect s of f luid regulation and digesti v e fu nctions ar e suspended when bl ood f lo w is rou ted awa y f rom viscer al orga ns to ward t he muscl es. Hormones tha t regulat e ex tr acellula r f luid v ol ume in a se denta r y steady state a r e applied to ward suppor ti ng and en ha ncing cir culator y fu nction ( see chapter 3 ). Suprahomeostat ic concentrations of metabolic fuels may be mob il ize d at h igh e xercise intensities in ant ici pation of ener gy ne eds. Both hor mones and the A NS comple ment the f unction of the other, and they fre quently intera ct. Cer ta i n hormones ca n modulate autonomic f unction, as i llustrat ed by induction o f S ad renergic receptors ( AdR ) b y thyroxine ( T 4 ) . Au tonomic nerves, on the other ha nd, i n f lu - ence secr etion o f ma ny h or mones. Dur i ng e xercise , S ner v es suppress secret ion o f insul in and facil itate se cretion of glu cagon and ad renal E . S ner ves also in f luence the t im i ng of ma ny ph y si ol ogical and endoc r ine f unctions. In b oth t he endocr ine system and t he A NS, ad justments in body f unctions a re auto- matic a nd largel y bey ond consci ous detect ion or co ntrol. W e a re not a ware of endocr ine or autono m ic adj ustments in concentr ations of metabolic fuels or in plasma v ol ume ( PV) and osmo lar ity . T he k nown e xceptio ns to th is genera li zation ar e ra re but note worthy . Re lease of ch olecy stokin i n ( CCK) in response to eat ing a mea l r ich in protein a nd fat is associated with sensations of satiation, which can be reproduce d by intrav enous in jection of the hor - mone i tself ( Little et al., 20 05) . Loss of p lasma sod ium (Na ) a nd PV stimu lates sec retion of angiotensin II. T h is hor mone increa ses both t h i rst and preference f or salty solu tions and f ood. Agai n, t he effects can b e reproduce d by intrav enous or intracerebrov entr icular i njec- tion of the hormone ( Fi tzsimons, 1 998 ) . Although ma ny hormones hav e a ccess to a ll cells i n t he body th rough systemic ci rcula- tion, they achiev e their spe cif ic effects by possess ing dist inctiv e chemical pr oper ties a nd by b ind ing to stereospe cif ical ly and chemica lly matched re ceptors locate d either on cell membranes or i nside the cells or thei r nuc lei. A uto nomic ner ves secrete t heir neu rotr ans- m itters f rom axon ter m ina ls into a synaptic cle ft on t a rget or gans. T here, the autonomic neurot ra nsmitt ers act on membra ne receptor s.

[Advanced Exercise Physiology] Katarina Borer - Advanced Exercise Endocrinology (2013, Human Kinetics)

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