3. Introduction
•Endocrine system is made up of glands that produce and secrete hormone, chemical substances
produced in the body that regulates the activity of cell and organs.
• information transferred from one part of body to another. Ex: nervous system(electric impulse),
endocrine system ( using chemicals )
• Glands
1. Exocrine glands / duct glands
2. Endocrine glands / ductless glands
4. Exocrine gland
•It has ducts or canals through which they pour out their secretions.
•E.g Lacrimal & sebaceous gland
Endocrine gland
•It pour their secretions called hormones directly into the blood stream.
6. Hormones
• Hormone : The chemical substances which are formed in endocrine gland and are carried by
blood stream to another organ, where it has an effect on its functions, growth and nutrition are
termed as hormones.
•Circulating hormone: Hormones carried by blood stream to distant target cells.
•Local hormone: hormones that act on target cells close to their site of release.
•Chemically the hormones can be classified into four classes
Steroids Biogenic amines Peptides and Proteins Eicosanoids
7. • Steroids : These have steroid nucleus and are derived from cholesterol. They are synthesized on
smooth endoplasmic reticulum. E.g aldosterone, cortisol
•Biogenic amines: Synthesized from amino acids e.g dopamine, Histamine , Serotonin
•Peptides and proteins: They are synthesized on granular endoplasmic reticulum and consist of
chain of amino acids e.g insulin, glucagon
•Eicosanoids: They are derived from arachidonic acid e.g prostaglandins, leucotrienes
8. Mechanism of hormone action
• Receptors
• diagram
• The circulating blood transports the hormone
to all cells in body
• only those cell possessing the hormone
receptor respond to hormone
• Other cells of body do not respond
9. ACTION ON PLASMA MEMBRANE RECEPTOR
Diagram
ACTION ON INTRACELLULAR RECEPTOR
Diagram
10. ACTION ON PLASMA MEMBRANE RECEPTOR
• The free fraction of hormone binds to the
receptor, this binding activates g protein
molecule, then it activate intracellular enzyme
adenyl cyclase it converts ATP into cAMP
•This cAMP activate the protein kinase
activated protein kinase phosphorylates other
enzymes in the cell.
•Phosphorylated enzymes catalyze reactions that
produce physiological response
ACTION ON INTRACELLULAR RECEPTOR
•The fat soluble steroidal hormones enter the
target cells and binds to the receptor usually
present in the nucleus
• This hormone receptor complex then through
gene expression forms new messenger RNA
(mRNA)
•Under the direction of mRNA new protein will
be synthesized by ribosomes
•This new protein initiate change in cell activity
which is characteristic of hormone.
11. Control of hormonal secretion
Negative feedback Mechanism
• Hormone production and release is mainly
controlled by negative feedback mechanism
•Once the level of hormone reaches certain
levels it sends signal to stop further release
12. • The three mechanism of hormone release
1. Humoral stimuli
2. Hormonal stimuli
3. Neural stimuli
• Hormone destruction
13. Pituitary gland (Master gland)
Diagram
• Located beneath the brain in the sella Taurica
of sphenoid bone.
• It consist of two lobes
1. Anterior lobe
2. Posterior lobe
17. Posterior pituitary gland
1. Antidiuretic hormone (ADH)
• ADH promotes reabsorption of water by kidney and pressor effect and stimulate involuntary
muscle
• Release of ADH depends on body’s hydration
• Chane in osmotic pressure of blood
• Osmoreceptor stimulate the
production & release of ADH
Low water
content
• Osmoreceptors inhibit the production
and release of ADH
High water
content
18. 2. Oxytocin
• Play important role during and after birth of baby.
• During birth it stimulate the contraction of smooth muscles of uterus
• After birth it stimulate the contraction of Myoepithelial cells
•Large amount of oxytocin released during labour and delivery
19. Thyroid gland
• Largest endocrine gland
• Consist of two lobes
• Two lobes are connected by thin band of tissue on
anterior side called as isthmus
• Follicular cells secrete hormones, thyroxin and
triiodothyronine
• Some follicular cells secrete hormone, calcitonin
21. 1. Iodine absorbed from gastrointestinal tract appears in the blood as inorganic iodide. The
follicular cells of thyroid gland take up this iodine. The iodide ions are oxidized in the
follicular cells and the elemental iodine formed is secreted into lumen of the follicle.
2. The follicular cells synthesize thymoglobulin (TGB) that contains tyrosine as one of thw
amino acids. The follicular cells secrete the TGB into the lumen of follicle. The lumen
containing TGB and iodine is called as colloid.
3. In colloid, the iodine attaches to tyrosine residue of TGB. Binding of iodine yields as
monoiodotyrosine (MIT) and second iodination gives diiodotyrosine(DIT). Further MIT and
DIT join to form thyroxin
4. The colloid containing this hormones is then taken up by follicular cells by pinocytosis. On
stimulation by TSH these hormones are released by diffusion through membrane into blood
stream. In blood the thyroid hormones are bound to plasma protein known as Thyroid Binding
Globulin (TBG)
22. Disorders of thyroid gland
1. Cretinism: hyposecretion of hormone leads to failure in the development of skeleton and
brain
2. Myxedema: In adults hyposecretion leads to myxedema which is characterized by puffiness
of the face and eyelids and swelling of tongue and larynx
3. Thyrotoxicosis: it is a condition in which excess of thyroid hormone characterized by
increase in body temperature and heart rate.
4. Grave’s disease: condition in which thyroid gland enlarges and produces large amount of
thyroid hormone.
5. Goiter: The dietary deficiency of iodine results into decreased levels of thyroid hormone in
blood, this results into increased secretion of TSH under the influence of which the thyroid
gland enlarges.
23. Parathyroid glands
• They secrete protein hormone called as
parathyroid hormone / Parathormone
• It’s role is to maintain the level of calcium in
blood.
24. Hypersecretion
leads to increase
plasma calcium
level and
decalcification of
bone occurs
Hyposecretion
leads to decrease
in calcium vel
which causes
muscle spasm
and twitching
Hyperparathyroidism
Hypoparathyroidism
25. Adrenal Gland
• Two glands located on superior portion of
each kidney
•Each gland has two distinct part
1. Adrenal medulla- Inner part
2. Adrenal cortex- Outer part
26. ADRENAL CORTEX
• A gr. of steroid hormone secreted by adrenal
cortex are called as corticosteroids.
1. Mineral Corticoids
2. Glucocorticoids
3. Gonad Hormones
ADRENAL MEDULLA
• It secretes two hormones both having
catechol nucleus and amino gr.
•The hormone are called as epinephrine and
nor-epinephrine
27. MINERAL CORTICOIDS
Physiological Role
• Secrete aldosterone
• Regulate electrolyte balance
• Maintain water balance of body
• Increase reabsorption of sodium
• Promote loss of potassium and hydrogen in
urine
GLUCOCORTICOID
Physiological Role
• Secrete cortisol, cortisterone, cortisone
• Promote gluconeogenesis
• Reduce protein storage
• Promote fat metabolism
28. • Gonad Hormone: Secreted by adrenal cortex, having influence on sex organ
Adrenocortical Disorder
Hypersecretion:
Cushing Syndrome
Hyposecretion:
Addison’s Disease
31. • It is both exocrine and endocrine gland
•The endocrine portion of gland consist of groups of tiny cells scattered in exocrine portion.
•These cells are known as islets of Langerhans, four types of such cells have been identified
secreting different hormones.
Alfa cells : Glucagon
Beta cells : Insulin
Delta cells : somatostatin
F-cells : Pancreatic polypeptide
32. • Beta cells secrete insulin
•Physiological role of insulin: glucogenesis, Lipogenesis, decrease blood glucose levels
Insulin
• alfa cells secrete glucagon
•Physiological role: glycogenolysis, glyconeogenesis, decrease blood glucose levels
Glucagon
•Delta cells secreate somatostatin, it inhibit secretion of alfa and beta cells
Somatostatin
• F cells secrete the pancreatic polypeptide
• it regulate release of pancreatic hormone
Pancreatic Polypeptide
35. Pineal gland
• it secretes hormone called as melatonin
Thymus gland
• The hormone produced by thymus gland
1. Thymosin
2. Thyme factor
3. thymopoeitin
