1. Hormone
(Gk horman, ‘ to stir up or excite’)
Ernest Henry Starling: In 1905 coined the term HORMONE in his famous lecture
‘The chemical correlation of the functions of the body’
Hormones are produced by Special cells or glands
• Pancreas & intestinal mucosa
• Adrenals, ovaries, testes, parathyroid, pituitary, and thyroid gland
Endocrine glands: secrete directly into the blood stream
Exocrine glands: Tears, sweat, digestive enzymes outwards
2. Hormone: Chemicals Messengers
Hormones
• Carry messages from glands or special cells to
target cells
• Hormones are chemical messengers that
coordinate different functions in the body. Several
glands, organs and tissues make and release
hormones, many of which make up endocrine
system.
• Hormones are extremely potent & produced in
very small amounts
3.
4. Target cells refer to cells that contain specific receptors (binding sites) for a particular
hormone.
Once a hormone binds to receptor on a target cell, a series of cellular events occur
5. Receptor
A protein molecule, embedded in either the
plasma membrane or the cytoplasm or
nucleus of a cell, to which a mobile signaling
molecule may attach
Intracellular receptors
Steroid hormones
Derivatives of vitamin D₃,
retinoic acid, and thyroid hormones
Modulate gene expression
Plasma membrane receptors
Protein/peptide hormone
catecholamine
6. Hormonal signals
integrate and coordinate the metabolic activities
Every process - regulated by one or more hormones
• Maintenance of blood pressure
• Blood volume
• Electrolyte balance
• Embryogenesis
• Sexual differentiation
• Development & Reproduction
• Hunger, eating behavior, digestion
• Fuel metabolism
7.
8. Classification of hormones
Hormonal communications are classified according to the distance over which
the signal acts
• Endocrine
• Paracrine
• Autocrine
Based on their chemical structure
• Water soluble: Peptides or proteins, Catecholamines
• Lipophilic: Steroid hormones, Vit D, Retinoic acid, Thyroid hormones,
Eicosanoids
Based on their modes of action
• Slow acting & Fast acting
9. (b) paracrine signals are directed at nearby
cells e.g. Eicosanoid hormone
(a) Endocrine signals are directed at distant cells
through the intermediacy of the bloodstream
C. autocrine signals are directed at the cell
that produced them
10. Classes of hormones in mammals, distinguishable by their
chemical structure and their modes of action
11. Slow-acting hormones act
through Nuclear receptors
Hydrophobic molecules readily
pass through the plasma
membrane of target cells and
bind to intracellular receptors.
Fast acting
Hormones act
through cell
surface receptors
12. Peptide Hormones
3 -200 or more amino acids
All hormones of hypothalamus and pituitary
Pancreatic hormones insulin, glucagon, and somatostatin
Parathyroid hormone, calcitonin
Gastrin, Secritin, Cholecystokinin (CCK),
Gastric Inhibitory pepetide (GIP), Chorionic gonadotropin (CG)
Prohormones, secretary vesicles, cleaved to form active peptides
15. Eicosanoids, paracrine hormones
Prostaglandins, thromboxanes, and leukotrienes
Arachidonate is precursor for Eicosanoids
not synthesized in advance and stored but
produced when needed
Enzymes that produce eicosanoids are
widely distributed, Most cells can produce them
Many tissues respond to them
Prostaglandins: Pain & Inflammation, Contraction of smooth muscles( Intestine & Uterus) Anti-
inflammatory drugs inhibit synthesis of PGs
Thromboxanes: Regulate Platelet function & Blood Clotting
Leukotrienes ( LTC4, LTD4): Contraction of smooth muscle in Intestine, Pulmonary airways &
Trachea, Mediators of anaphylaxis ( severe ,detrimental response)
Phospholipase A2
21. Retinoid Hormones Potent hormone
nuclear retinoid receptors
Regulate the growth
Survival & differentiation of cells
• cornea,
• skin,
• epithelia of lungs & trachea,
• immune system
RA regulates
the synthesis of proteins essential
for growth or differentiation
Liver
Many tissues
Targets of retinoic acid are All tissues
23. Stable free radical: Molecular oxygen & guanidino nitrogen of arginine
NO synthase (NOS),
It is present in many tissues and cell types like neurons, macrophages,
hepatocytes, myocytes of smooth muscle, endothelial cells of the blood vessels,
and epithelial cells of the kidney.
It acts near its point of release, cytosolic guanylyl cyclase, cGMP
NO synthase ( NOS)
Nitric Oxide (NO)
24. https://www.youtube.com/watch?v=TgNwxF3aQpE
Mechanism of Hormone Actions at Cell Surface Receptor
https://www.youtube.com/watch?v=UhZB6aBJM-w
https://www.youtube.com/watch?v=bEtZHeCPsBs
https://www.youtube.com/watch?v=PUXkZ-tJSp8
https://www.youtube.com/watch?v=m9jOXiYdMeY
Replication
https://www.youtube.com/watch?v=TNKWgcFPHqw
Transcription
https://www.youtube.com/watch?v=gG7uCskUOrA
Editor's Notes
FIGURE 19-1 Classification of hormones. Hormonal communications are classified according to the distance over which the signal acts: (a) endocrine signals are directed at distant cells through the intermediacy of the bloodstream, (b) paracrine signals are directed at nearby cells, and (c) autocrine signals are directed at the cell that produced them. (Voet & Voet, 2005).
