HORMONE PRODUCTION AND STORAGE DR AMNA TAHR ASSISTANT PROFESSOR PHYSIOLOGY DEPARTMENT KEMU

HORMONE A hormone is a chemical substance produced in particular parts of organisms by specific cells, glands, and/or tissues and then transported to other parts of the body, with the intent of influencing a variety of physiological and behavioral activities, such as the processes of digestion, metabolism, growth, reproduction and mood control. digestionmetabolismgrowthreproductionmood

ENDOCRINE SYSTEM The endocrine system is a ductless system referring to the collection of cells, glands, and tissues of an organism that secrete hormones directly into the bloodstream to control the organisms' physiological and behavioral activities.cellsglandstissuessecretehormones The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts.exocrine systemducts The word endocrine derives from the Greek words "endo" meaning inside, within, and "crinis" for secrete.

ENDOCRINE ORGANS

MAJOR CLASSES OF HORMONES 1- Protein and peptides including hormones secreted by anterior and posterior pituitary, the pancreas, parathyroid gland 2- Steroids secreted by the adrenal cortex, the ovaries, testes 3- Derivative of the amino acid tyrosine, secreted by thyroid gland, adrenal medullae.

HORMONE PRODUCTION AND STORAGE Polypeptide and protein hormone are stored in secretory vesicles until needed. Steroid hormones are usually synthesized from cholesterol and not stored. Amine hormones are derived from tyrosine

FEED BACK CONTROL OF HORMONE SECRETION Negative feedback mechanism  Is most commonly applied principle for regulating hormone secretion  It prevents over activity of the hormone system  Is self -limiting  A hormone has biologic actions that, directly or indirectly, inhibit further secretion of the hormone

FEED BACK CONTROL OF HORMONE SECRETION Positive feedback mechanism  is rare  Is explosive and self – reinforcing  Surges of hormone can occur with positive feed back  A hormone has biologic actions that, directly or indirectly, cause more secretion of the hormone

MECHANISM OF ACTION OF HORMONE Hormone receptors and their activation Location of receptors for different hormones  In or on the surface of cell membrane for protein, peptide and catecholamine hormones  In the cell cytoplasm for steroid hormones  In the cell nucleus for thyroid hormones

INTRACELLULAR SIGNALING AFTER HORMONE RECEPTOR ACTIVATION Ion Channel –linked receptors G-Protein-linked Hormone receptors Enzyme-linked hormone receptors

Ion Channel –linked receptors

G-Protein-linked Hormone receptors

Enzyme-linked hormone receptors

SECOND MESSANGER MECHANISM  AdenylCyclase – cAMP second messenger system  Cell Membrane Phospholipid second messenger system  Calcium -Calmodulin second messenger system

 AdenylCyclase – cAMP second messenger system

 Cell Membrane Phospholipid second messenger system

Mechanism of interaction of lipophilic hormones