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ENDOCRINE PHYSIOLOGYIrawan YusufDepartment of Physiology Faculty of Medicine Hasanuddin Univeristy
Communication systems between cellsNervous systemGenerally controls rapid activitiesTransmits information quicklyRelatively short duration of effectEndocrine systemGenerally controls rates of cellular metabolism, growth and reproduction, transport across cell membranesTransmits information more slowlyEffects tend to last much longer
Endocrine gland A cell or a group of cells that secretes a chemical messenger, called a hormone, directly into the bloodstream
Endocrine hormoneA chemical messenger that is produced by 1 cell or a group of cells, secreted directly into the bloodstream and transported to distant target cells, in which it elicits a typical physiological response
Neurocrines (neurohormones)Chemical messenger secreted by axonal terminal of neuron directly into bloodstream:Transported to and acts on relatively distant target cellNeuron
ParacrineA chemical messenger secreted by a cell into ISF that acts on a different type of neighboring cell type
AutocrineA chemical messenger secreted by a cell into ISF that acts on the cell of origin or a neighboring identical cell type
FUNCTION OF ENDOCRINE SYSTEMControl systems, maintain homeostasis:control chemical and water balance in bodycontrol growth and metabolismcontrol embryonic development and preparation for nurturing a newborn influence sexual behavior, stimulate growth and maturation of the gonads
HomeostasisProcess of maintaining the composition of the internal body compartments within fairly strict limits (ion concentrations, pH, osmolarity, temperature etc)Require regulatory mechanisms to defend against changes in external environment and changes due to activityCellular homeostasis - intracellular fluid composition Organismal homeostasis - extracellular fluid compositionCardiac muscle cell contraction electrical signals intracellular and extracellular [Na+], [K+] and [Ca2+]If extracellular [K+] too high depolarisation contraction fibrillation (bag of worms) Extracellular [K+] must be kept within narrow range
Desired concentration range for each chemical constituent of body regulatory mechanisms
eg Blood [glucose] 4-5 mmol.l-1if [glucose] >> 5 mmol.l-1 insulin secretion [glucose]if [glucose]
Negative feedback loopNegative feedback loop requires:Sensor specific to variable needing to be controlledComparator reference point for sensor to compare againstEffector if sensor comparator Error Signal restore variable to desired levelComparator(reference point)EffectorControlledvariable SensorDisturbanceErrorsignal
Limitations of negative feedbackNegative feedback control initiated after variable has been disturbedAmount of correction to be applied assessed by magnitude of error signal incomplete correctionOvercorrection oscillations in controlled variable
Disadvantages overcome by multiple regulatory mechanisms
egregulation of blood [glucose]insulin [glucose]bloodglucagon [glucose]blood
Positive feedbackNegative feedback - error signal reduce deviation from reference pointPositive feedback - error signal increase deviation from reference point (vicious circle)
errorsignal
Homeostasis in Summary
Endocrine hormone classificationPeptide hormones Peptides, polypeptides, proteinsProduced by:Pituitary glandHypothalamusParathyroid glandPancreasFetal membranes (placenta)Endometrium
Steroid hormonesDerived from cholesterolProduced by:GonadsAdrenal cortexFetal membranes Biogenic amines hormonesDerived from tyrosineProduced by:Thyroid glandMedulla adrenal
Steroid hormonesIntracellular receptorsInteraction of hormone and receptor usually results in or synthesis of specific proteins in target cellEffect occurs in minutes to daysDuration of effect hours to days
Steroid hormonesIntracellular or nuclear receptorsInteraction of hormone and receptor usually results in or synthesis of specific proteins in target cellEffect occurs in minutes to daysDuration of effect hours to days
Biogenic amine hormonesIntracellular or nuclear receptorsInteraction of hormone and receptor usually results in or synthesis of specific proteins in target cellEffect occurs in minutes to daysDuration of effect hours to days
AngiotensinogenAngiotensin IAngiotensin IIIntake NaCl Tekanan darah Volume CES Stres/TraumaMakula Densa, Baroreseptor, Susunan Saraf SimpatisSel JuxtaglomerularReninACEAdrenalGinjalP. DarahOtakFaktor PertumbuhanAldosteronReabsorbsi NaVasokonstriksiVasokonstriksiAliran darahReabsorbsi NaTahananPeriferJantungKontraksiADHSimpatis
Proliferasiotot polos
Menstrual cycle: plasma hormone levels in relation to ovulation
Oxytocin Production During Parturition
Oxytocin and Prolactin Production During Suckling