Download HORMONE PRODUCTION AND STORAGE

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.
•
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 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
SECOND MESSANGER MECHANISM
AdenylCyclase – cAMP second messenger
system
Cell Membrane
messenger system
Phospholipid
Calcium -Calmodulin second
system
second
messenger
 AdenylCyclase – cAMP second messenger
system

Cell Membrane
messenger system
Phospholipid
second
Mechanism of interaction of lipophilic
hormones