PHYSIO LECTURE 3 part a.pptx endocrine system

Endocrine system slides by cool education

1. ENDOCRINE SYSTEM PART I Cool Education Nursing Academy

2. REFERENCE TEXTBOOK Guyton and Hall – textbook of medical physiology UNIT XIV, CHAPTER 75 (Introduction to Endocrinology)

3. LECTURE OUTLINE Introduction Hormone classification Peptide and protein hormones Steroid hormones Amine hormones Regulation of hormone level in blood Hormone receptors

4. INTRODUCTION

5. Endocrine system consists of several glandular structures in the body which are specialized to synthesize and secrete special chemicals (called hormones) into the circulation. In addition to these specialized structures, other organs (like kidney, heart, adipose tissues, liver) also exhibit endocrine function and secrete hormones into the circulation. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

6. 1. Hypothalamus. 2. Pituitary gland (anterior & posterior lobes ). 3. Thyroid gland 4. Parathyroid gland 5. Adrenal cortex and adrenal medulla 6. Pancreas (Islets of Langerhans ) 7. Testes 8. Ovaries Endocrine Glands Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

7. Kidney – Erythropoietin(major role in formation of RBC), 1 ,25-Dihydroxycholecalciferol, Renin . Heart – Atrial natriuretic peptide (ANP). Stomach – Gastrin. Small intestine – Secretin, Cholecystokinin (CCK). Placenta – Human chorionic gonadotrophin ( hCG ), Estrogen, Progesterone. Adipocytes – Leptin Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

8. Functions Maintenance of homeostasis. Growth and development. Reproduction. Maintenance of blood pressure. Maintenance of concentration of different ions and other substances in the blood. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

9. HORMONE CLASSIFICATION

10. Introduction A hormone is a chemical substance secreted into the circulation in very small amounts and are delivered to target tissues where they produce various physiologic responses. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

11. Classification On the basis of chemical structure, hormones may be classified into 3 categories : Proteins and polypeptides. Steroids. Amines (derivatives of amino acid tyrosine ) Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

12. PEPTIDE AND PROTEIN HORMONES

13. DNA mRNA (Transcription) Preprohormone (Translation) Prohormone Hormone Synthesis N uc l eus RER SER Golgi Apparatus Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

14. Storage The hormone is stored in secretory vesicles within cytoplasm and is secreted by exocytosis in response to appropriate stimulation. Transport They are water soluble and are transported into the blood in dissolved form . Receptors Examples Hormones secreted by: Anterior pituitary. Posterior pituitary. Hypothalamus ( except PIF=Prolactin inhibitory factor). Parathyroid gland. Pancreas. Examples also include calcitonin , renin, erythropoietin, ANP, gastrin, secretin, CCK and leptin. Receptors for peptide and protein hormones are located in or on the surface of cell membrane of the target cell.

15. STEROID HORMONES

16. Chemical Nature Derivatives of cholesterol. Lipid soluble . Synthesis On appropriate stimulation of the cell, large stores of cholesterol esters in cytoplasmic vacuoles are rapidly mobilized for steroid synthesis. . Storage Because of high lipid solubility, they are not stored within the cell and immediately diffuse across the cell membrane after their synthesis . Transport They are not soluble in water and are transported into the blood bound to plasma proteins. Receptors Receptors for steroid hormones are found mainly in the cytoplasm of the target cell. Examples Hormones secreted by: Adrenal cortex. Testes. Ovaries. It also includes 1,25-dihydroxycholecalciferol

17. AMINE HORMONES

18. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392 Chemical Nature and Synthesis Derived from an amino acid tyrosine. Formed by action of enzymes in the cytoplasm of endocrine cells. Amine hormone classified into two hormone: 1-Thyroid hormone 2-Catecholamine

19. Storage Thyroid hormones- incorporated into another protein called thyroglobulin for storage, secretion occurs when amines are split from thyroglobulin Catecholamine- Stored into secretory vesicles and released by exocytosis Transport Thyroid hormones – They are transported into the blood bound to plasma proteins thyroid (binding globulin) 2. Catecholamine – They are water soluble and are transported into the blood in dissolved form Receptors Thyroid hormone – Receptors for thyroid hormone are found in the nucleus of the target cell in direct association with chromosomes Catecholamines – Receptors for catechol amines are found in the cell membrane of the target cell. Examples Thyroid hormones (T3, T4). Catecholamine (adrenaline and noradrenaline). Prolactin inhibiting factor (PIF). Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

20. REGULATION OF HORMONE LEVEL IN BLOOD

21. Mechanisms Hormone concentration in the blood can be regulated by 2 factors: Regulation of rate of hormone secretion into the blood. Regulation of rate of hormone removal from the blood. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

22. Hormone secretion by endocrine cells into the blood is regulated by one of the following mechanisms: Neural mechanism. Chemical mechanism. Feedback mechanism. Negative feedback mechanism. Positive feedback mechanism Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392 Regulation of Hormone Secretion

23. Neural mechanism Secretion of a hormone in response to a nervous signal. Example – Secretion of catecholamine from adrenal medulla in response to neural stimulation by preganglionic sympathetic nerves . Chemical mechanism Secretion of a hormone in response to an extracellular chemical c hange, Examples are Secretion of insulin and glucagon – Changes in glucose concentrations. Secretion of parathormone and calcitonin – Changes in calcium concentration. Secretion of ADH – Changes in blood osmolality .

24. Positive feedback If some feature of hormone action causes more secretion of the hormone, it is called positive feedback mechanism. This is Relatively uncommon, Examples include: Ovulation – Estrogen increases LH and FSH production which further increase estrogen secretion. Labour – Dilatation of cervix causes increased secretion of oxytocin which further dilates the cervix. Feedback mechanism Conditions or products resulting from physiologic action of a hormone, directly or indirectly, modulates its further secretion from the endocrine gland. This is called feedback control. It could be: Negative feedback – More common Positive feedback – Less common Negative feedback If further secretion of a hormone is suppressed by conditions or products resulting from physiologic action of that hormone, it is called negative feedback mechanism. Secretions of almost all the hormones are controlled by negative feedback mechanism.

25. The rate of removal of hormone from the blood is called metabolic clearance rate. Hormones are “cleared” from the plasma in one of the following several ways: Metabolic degradation by tissues. Binding with tissues. Excretion by liver into bile. Excretion by kidneys into urine. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392 Regulation of Hormone Removal

26. HORMONE RECEPTOR

27. Hormonal receptors are the proteins which are located in or on cell membrane, or in cytoplasm or in nucleus of the target cell. Each receptor can bind to only a specific hormone. A target cell that lacks receptors for a hormone is nonresponsive to that hormone. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392 Receptors

28. How Receptors are Regulated? Number of receptors on a target cell does not remain constant . They are continuously subject to either one of the following 2 mechanisms: Down regulation - Decrease in the affinity or number of active receptors. Up regulation - Increase in the affinity or number of active receptors. Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

29. Down regulation Increased hormone concentration → Increased binding with target cells → Decreased number of active receptors (due to inactivation or degradation). Downregulation of the receptors decreases tissue responsiveness to the hormone. Up regulation Increased number of active receptors (due to increased production of receptors or intracellular signaling proteins). Target tissue becomes more sensitive to the effects of hormones.

30. SUMMARY Join Our Online Classes For BSN & AHS Exams Preparation 0304-3447392

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