HORMONE PRODUCTION AND STORAGE DR AMNA TAHR ASSISTANT PROFESSOR PHYSIOLOGY DEPARTMENT KEMU
Jan 08, 2018
HORMONE PRODUCTION AND STORAGE
DR AMNA TAHRASSISTANT PROFESSOR
PHYSIOLOGY DEPARTMENTKEMU
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.
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.
• The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts.
• 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 gland2- Steroids secreted by the adrenal cortex, the ovaries, testes3- 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 mechanismIs most commonly applied principle for
regulating hormone secretionIt prevents over activity of the hormone systemIs self -limitingA hormone has biologic actions that, directly
or indirectly , inhibit further secretion of the hormone
FEED BACK CONTROL OF HORMONE SECRETION
• Positive feedback mechanismis rare Is explosive and self – reinforcingSurges 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