5 Endocrine & Neuroendocrine: The Long Distance Travelers
6 Types of Cellular Secretion of Hormones Types of HormonesAction of HormoneExampleAutocrineActs on cells that synthesized themInsulin-like Growth Factor (IGF-1)-stimulates cell division in the cell which produced it.ParacrineActs on nearby cellsInsulin, secreted by pancreatic βcells-affects secretion of glucagon by pancreatic α cellsEndocrineCarried in bloodstream or thru lymph to target cells in organsInsulin, Estradiol, CortisolNeuroendocrineHormones synthesized in neuron:a) releases hormone next totarget cell ORb) releases it into bloodstream,which carries it to target cell.Hormone synthesized in neuron, goes from hypothalamus to anterior pituitary gland thru the portal systemNeuralChemical released by 1 neuron, & acts on adjacent neuron.Neurotransmitters: AcetylcholinePheromonalRelease of volatile hormones (into atmosphere; are transmitted to another individual & recognized as olfactory signal.Pheromones
7 Regulation of Hormone Secretion: NEGATIVE FEEDBACK If hormone A acts to raise the plasma concentration of substrate B, a decrease in substrate B will stimulate the secretion of hormone A.Whereas an increase in substrate B will suppress secretion of hormone A.Maintains homeostasis.
9 Blood Transport of Hormones When hormones are secreted into blood, many are immediately bound to plasma proteins.Proteins can recognize hormone specifically & bind it w/high affinity (ex: binding of sex hormones by sex hormone binding globulin- SHBG).
10 Blood Transport of Hormones Equilibrium btw free & bound hormonea fixed proportion of hormone travels free/unbound, while most is carried bound.Bound hormone isphysiologically inactiveprotected from metabolic enzymes in organs (liver)Drugs, (aspirin) can displace other substances like anticoagulants from their binding sitesmay cause hemorrhage.
11 General Mechanisms of Hormonal Action Hormones interact w/target cells thru primary interaction w/receptors that recognize the hormones.Several receptor systems: differ in mechanism & timing.1) Membrane Receptors2) Intracellular Receptors
12 MEMBRANE RECEPTORS conformational change in other membrane proteins Charged ions (peptides, neurotransmitters)bind to receptors oncell membraneconformational change inother membraneproteinsactivates enzymes in cellSynthesis of second messengersthat activatephosphorylating enzymes
13 Uncharged molecules (steroid hormones) INTRACELLULAR RECEPTORSUncharged molecules (steroid hormones)diffuse into cell &bind to intracellular receptorshormone-receptor complexbinds to specifichormone response elements (HREs)on DNAModulates gene expressionin target cell.RNA & protein synthesis altered.
14 TO WRAP IT UP: Types of Cell Secretion Blood Transport AutocrineParacrineEndocrineNeuroendocrineNeuralPheromonalBlood Transportbinding of hormone to plasma proteinMembrane ReceptorsIntracellular Receptors
15 BibliographyEndocrinology-At A GlanceMedical Physiology-Guyton