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