L13 endoc sys Flashcards
LO2: disc eg’s of biol rhyth.
-set pt of contr centre can vary. Circad/diurnal. Biol clock SCN. Env zeitgebers keep 24 HR cyc- light, temp, soc interac, exerc, eat/drink. Jet lag Mism btw zeitgebers and bod clock.
Eg core bod temp. cortisol peak morning so have stand time for meas. Melatonin from pineal gl int in sett clock. Me str cyc biol rhyth. Sudd incr core temp=ovulat. Hum nat diurnal cyc 24hr 11min.
-bod water homeo eg of contr sys-
Tot water 50-60% men, 45-50% fem. newborn 70%. Obese lower.
3 main compartment- intracell fluid 35%/28L, ECF 12%/9.4L, blood plasma 4.5%/4.6L= 42L in 70kg man. Osmot press of blood monit by osmoRs in hypoth.
-osmolarity vs osmolality-
Osmolarity= osmoles per L. VOL.
osmolality= osmoles per kg sol. MASS.
Osmole= amnt of subst that dissocs in sol to form 1 mole osmot active partics eg 1mM so NaCl= osmolarity 2mOsmol/L (1 from each ion). Serum osmolality usef when investig hyponat. Ref blood osmolality 275-95mOsmol/kg.
-ADH- diag.
Movem water btw comparts gov part by osmot press- careful contr in set lims.
LO3: define horm and list feats of comm procs inv horms.
-endoc sys= collec gl through bod.
Horm= chem sig prod in endoc gl/tiss that trav in blood to effect other tiss. Norm low conc 10^-10 M. Poss bound to carrier prot. Us change in horm conc triggs resp.
Maj endoc gl- most discrete strucs eg hypoth, pineal, pit, thyr, PT, thymus, adren, ovary, testis. Some collects cells eg panc islets, other organs and tiss rel horms- heart atrial naturetic pep and BNP, regul BP. Liver IGF-1. Stom gastrin and ghrelin. Placenta inhibin, placental lactogen. Adip leptin. Kidn renin and calcitriol.
-comm mechs-
Autocrine horm act on cell of ori. Paracrine sig carried to adj cell same type and locat by interstit fluid. Endoc horm sig rel to blood carried to dist targ cells. Neurocrine- horm ori in neurone and after transp down axon is rel to blood and carried to dist targ cells. Imp in HAP.
-endoc and NS sev sim feats-
Neurons and endoc cells both sec. Both excitable- can be depol=mem poten less neg=AP in neuron, horm sec in endoc. Some molecs act as both eg drop aka prolactin inhib horm. MOA reqs interac specif Rs in targ cell. Sys work in paral to contr horms.
Endoc sig horm, NS nt and AP. Endoc chem, NS chem and elec. endoc convey blood, NS synapse and axon. Both med by Rs. Endoc slow, NS fast.
LO4: list classes of horm.
- pep/pp largest grp- short chain AA eg insulin, glucagon, GH, placental lactogen.
Endoc gls that prod pep horms and cetacholamines norm store their horm prods in cell in discrete vesic bef sec.
Ster prod tiss store horm precurs chol as CE in lip drops. Thyr gl excep as stores horms outs cell as colloid.
-GP- large prot molecs. Often su’s. Carb s/c. Eg LH, FSH, TSH-sec by ant pit.
-pep and GP water sol Phillic, transp in blood plasma. Also adren medulla horms.
-AA derivs (amines)- small molecs synth from AA (tyrosine) eg adren, Na, thyr horms.
-steroids- all der from chol precurs. Eg cortisol, aldosterone, testosterone, oestrogen.
-ster and thyr horms phobic, need spec transp prots. 75% thyr horm norm bound to TBG, 25% non specif to alb. Low conc free horm.
-water vs lip sol determs type R.
LO5: desc how horms transp and act on targ cells.
-horm transp- some horms trav in blood in simp sol eg insulin, adren. Most horms bind prots, partic lip sol. Often specif prots eg thyroxine binding globulin. Dynam eq btw bound and free in plasma. Only free biol active.
Carrier prots- incr sol of horms and incr t1/2, readily accessible reserve.
-3 main facs in horm levs-
Rate prod- incr blood flow to partic organ= more horm deliv.
Rate deliv- incr blood flow to partic organ= more horm deliv.
Rate deg- metabol and excret. Sec rate must be adj to maint approp blood conc. Us by neg feedb- rate sec aff by blood conc directly or more likely by a conseq of blood conc. If conc corr=slower sec, conc decr=sec incr.
-horms exert effs by bind specif Rs. Targ cell exp R=specif cell resp.
-Water sol horms bind cell surf Rs- downstr sig path affs func. Can’t X mem. Fast acting. 2 Maj classes mem R-
GPCR- Maj drug targ. Eg adren R. Bind horm= dissoc G prot alpha su. Activ effector prot eg adenylyl cyclase. Format second mess eg cAMP. Activ prot kinase eg PKA. Plat targ prots. Cellul resp- activ enz/prot or exp genes.
Tyr kinase- eg insulin R. Tyr kinase domains inside mem. Bind=dimerisation (excep insulinR already dimer). AutoP of specif tyr. Rec adap prots and sig complex. Activ PKB. Plat targ prots. Cellul resp. Targ tiss us rap resp to horm that alt activ of func prot eg enz/mem transp.
-lip sol horms bind intracell Rs- cytos/nuc. Horm resp alt rate gene exp takes longer and can occ after horm conc back to norm.
Diffuse X PM. T1 cytop R bind horm and complex ent nuc and bind DNA. T2R in nuc, horm in and bind R already on DNA eg thyr horm bind relieves repress of transc=exp.
both Rs bind specif DNA seq- HRE in prom reg of specif genes. Exp of new prot meds effs of horm= cellul resp.
-some horms one Maj targ tiss eg TSH. Others many eg insulin to liv, musc, adip.
LO6: expl in gen terms how horm sec contr.
-HPA- complex func unit is Maj link btw endoc and NS. Pit under hypoth in sella turcica base skull. Post brain emb ori. Ant gl of same cells give rise to gut.
Mosul var procs togeth- growth, repro, adren gl func, water homeo, milk sec, lactat, thyr gl func, puberty.
Ant gl- adenohypophysis, oral ectod ori. Post neurohypophysis, neuroectod ori. Diff funcs. Infundibulum links pit to hypoth.
-neuroc func of post pit- neuroc OT from SON, and ADH from PVN. Transp down axons to post pit. Stored and rel to blood to act on dist targs. Pit NOT synth, just rel.
-ant pit func- dir comm hypoth and ant pit by blood infl endoc sec. Horms synth in hypoth down axons and stored in median eminence bef rel to hypophyseal port sys= stim/inhib targ ant pit endoc cells. Neuroc func. Ant pit also auto and paracrine func.
-so horms prod in hypoth act via 2 distinct neuroc paths-
Dir effs on distinct targ cells via OT and ADH from post pit.
Horms sec exclus to hypophyseal port sys aff ant pit endoc cells.
-2 horms prod in hypoth and rel by post pit- OT milk let down and uterus contrac. ADH bod water.
-7 tropic horms of hypoth-
Tropic horms have endoc gl as targ. Eff sec other horm. 7 tropic direct effs on rel ant pit horms- TRH, prolactin RH and IH, corticotropin RH, gonadotropin RH, GHRH, GHIH.
Trophic stim growth in targ tiss.
-tropic horms mostly sec by ant pit. Eg cortisol sec contr by ACTH. 6 main ant pit sec horms- TSH, ACTH adren cortex horms, LH ovul and sec sex horm, FSH div egg and sperm, PRL mamm gl dev and milk sec, GH growth and metab and stim IGFs.
TSH, ACTH, LH, FSH all tropic horms contr horm prod of other endoc. Sec of tropic horm somet contr by neg feedb eg TSH.
-ant pit summ diag.
-neg feedb eg TSH often to higher centre to inhib rel of RH. Paths prod ant pit and hypoth horms often neg feedb.
-HPA neg feedb- 2 levs-
ACTH inhib CRH hypoth rel. cortisol inhib CRH and ACTH rel. activ HPA in resp to stress.
-inactiv of horms occs in liv and kidn and somet targ tiss.
Ster inactiv by small struc change alt sol= excret urine or via bile.
Prot horms big chem alt, deg to AA and reused.
-horms regul dev, homeo, stress, stim etc.
Abn= thyr dis, DM, cushings, addisons, infert.
-disord endoc due to-
Alt endoc tiss= incr or decr sec horm or prod struc abn/ decr effec.
Responsiveness of endoc tiss alt by circ abn prot eg Ab.
Phys effec conc ECF by bind circ prot.
Alt resp of targ tiss due to alt R and/or post R events.
LO1: desc main feats of contr sys in bod
-homeo- mech bod contr env within set lims. Dynam eq.
Stim detec by R eg chemo, thermoreg, proprietary, nociRs.
Comm- NS AP, endoc sys horm. Afferent path of periph NS- sensory imp to brain. Efferent path motor output after contr centre.
Contr centre- us hypoth determ set pt. anal aff input. Determ resp. Hypoth in diencephalon- horm med oblongata in brain stem- ventil and CVS.
Effector- causes change eg sweat gl, musc, kidn. Rare pos feedb. Mostly neg feedb opp orig stim- output inhibs func of contr centre. Gives stabil to contr set pt. tend overshoot set pt sev times bef rest at set pt-hunting behav= dynam eq.
-neg feedb- Rev direc of change. Eg insulin.
Pos feedb- change variable even more in direc of change- rare, used when want rap change. Eg clott, ovulat. Output adds in to input. Ovulat builds up FSH= rel oocyte from follic.
