ENDOCRINE BASIC
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The document provides an overview of the endocrine system, including: - Hormones are chemical messengers that are secreted by endocrine glands and travel through the bloodstream to target organs to regulate physiological functions. - The endocrine and nervous systems both use chemical signals but differ in speed of response and duration of signal - the endocrine system is slower acting with longer-lasting signals compared to the rapid and brief nervous system. - Hormones have specific receptors on target cells and can cause effects through changing membrane permeability, gene expression, or second messenger systems. - Hormone levels are measured using bioassays, immunoassays like radioimmunoassay and ELISA, or dynamic
ENDOCRINE BASIC
- 1. ENDOCRINE SYSTEM DR.NILESH KATE. M.D. ASSOCIATE PROFESSOR, DEPARTMENT OF PHYSIOLOGY,
- 2. OBJECTIVES Hormone : definition, classification. Hormones general consideration. Hormone receptors & mechanism of action. Measurement of hormones.
- 3. HOMEOSTASIS & CONTROLS Successful compensation Homeostasis reestablished Failure to compensate Pathophysiology ○ Illness ○ Death Figure 1-5: Homeostasis
- 4. COMPARISON OF ENDOCRINE AND NERVOUS SYSTEMS. NERVOUS SYSTEM “WIRED” CHEMICAL SIGNAL AT TARGET CELL RAPID BRIEF DURATION CLOSE ANATOMICAL PROXIMITY ENDOCRINE SYSTEM “WIRELESS” CHEMICAL SIGNAL IN BLOOD. SLOW LONG DURATION SPECIFIC RECEPTORS
- 5. ENDOCRINE SYSTEM Hormaein-- Greek word means “to execute or to arouse”. Def:- Secretary product of ductless glands which are released in catalytic amounts into blood stream & transported to specific target cells where they elicit physiologic, morphologic & biochemical responses.
- 6. LOCATION OF DIFFERENT ENDOCRINE GLANDS.
- 7. Long Distance Communication: Endocrine Hormones Signal Chemicals Made in endocrine cells Transported via blood Receptors on target cells Figure 6-2a: Long distance cell-to-cell communication
- 8. TYPES OF HORMONES Functional ENDOCRINE HORMONES – Travel through the blood to act at a site distant from the secreting cell or gland PARACRINE HORMONES – Act on cells near the secreting cell AUTOCRINE HORMONES – Act on the secreting cell NEUROCRINE HORMONES – Secreted by neural cells ○ neurotransmitters ○ neurohormones
- 9. Figure 6-2b, c: Long distance cell-to-cell communication
- 10. Paracrine and Autocrine Hormones Local communication Signal chemicals diffuse to target Example: Cytokines Autocrine–receptor on same cell Paracrine–neighboring cells Figure 6-1c: Direct and local cell-to-cell communication
- 11. CHEMICAL CLASSIFICATION OF HORMONES Depending upon chemical nature Amines or amino acid derivatives: Proteins & Polypeptides: Steroid hormones Depending upon mechanism of action. Group I hormones. Group II hormones. : A,B,C,D.
- 12. HORMONE : GENERAL CONSIDERATION. Hormones chemistry, synthesis, storage & release. 1 Amines / amino acid derivatives 2 Protein & polypeptide hormones. 3 Steroid hormones.
- 13. HORMONE TRANSPOT, PLASMA CONC, HALF LIFE. Hormone transport. Unbound. Bound . Plasma concentrations. Peptide hormone 10 -12 mol/ L to 10-14 mol/L Epi / Nor Epi = 2× 10-10 to 13 × 10 -10 Steroid & thyroid 10-9 mol/ L & 10-6 mol/ L. Half life. Peptide hormone – short Steroid, & thyroid – long.
- 14. FUNCTIONS OF HORMONES. Regulation of biochemical reactions Regulation of bodily process.
- 15. HORMONE DISPOSAL. Target cell uptake & intracellular degradation. Metabolic degradation / inactivation. Urinary / biliary secretions. Metabolic clearance rate (MCR):- volume of plasma cleared per unit time.
- 16. REGULATION OF HORMONE SECRETION. Feedback control Neural control. Chronotropic control
- 17. FEEDBACK SYSTEM. Figure 6-26: Negative and positive feedback
- 18. Figure 7-14: Negative feedback loops in the hypothalamicanterior pituitary pathway NEGATIVE FEEDBACK REFLEXES : LONG , SHORT & ULTRASHORT LOOP.
- 19. HORMONES RECEPTORS. Characteristics Specificity . Location . ○Internal ○External . Regulation of number. ○Down regulation ○Up regulation .
- 20. STRUCTURE OF RECEPTORS. Recognition domain. Coupling domain.
- 21. CLASSIFICATION OF RECEPTORS. Receptor kinase Receptor linked kinase. G-protein coupled receptors. Ligand gated ion channels.
- 22. MECHANISM OF ACTION OF HORMONES. Through change in membrane permeability. Through effect on gene expression. Through second messengers. Through tyrosine kinase activation.
- 23. THROUGH CHANGE IN MEMBRANE PERMEABILITY. Hormones bind with external receptors. Conformational change in protein of receptors. Opening of Na, K, Ca channel. Movement of ions.
- 24. THROUGH EFFECT ON GENE EXPRESSION. Figure 7-7: Steroid hormone action
- 25. THROUGH SECOND MESSENGERS SYSTEM. Adenyl cyclase- cAMP system. Guanyl cyclase –cGMP system. Membrane phosplipase- phoapholipid system. Calcium- calmodulin system.
- 28. CA2+- calmodulin system (CONTINUED)
- 29. THROUGH TYROSINE KINASE ACTIVATION.
- 30. MEASUREMENT OF HORMONES. BIOASSAY. Injecting unknown sample of plasma in experimental animals & observing specific biological effect. IMMUNOASSAY.(AG-AB REACTION) RADIOIMMUNOASSAY ○ Mix Unknown sample of plasma containing hormone + purified specific antibody + purified hormone tagged with radioactive isotopes. ELISA ○ Instead of specific antibody, stained with suitable dye. & intensity of colour measured by spectrophotometer.
- 31. MEASUREMENT OF HORMONES. CYTOCHEMICAL ASSAY. Endocrine gland cut in slices Incubate in ascorbate enriched culture medium Genesis of hormone detected. DYNAMIC TESTS. Suppression type. Stimulation type.
- 32. ENDOCRINE REFLEX PATHWAYS: OVERVIEW Figure 7-9: Hormones may have multiple stimuli for their release
- 33. PATHOLOGIES: OVER OR UNDER PRODUCTION Figure 7-19: Negative feedback by exogenous cortisol
- 34. PATHOLOGIES: DUE TO RECEPTORS Figure 7-20: Primary and secondary hypersecretion of cortisol
- 35. Thank you