Endocrinology

Prof. K. Sivapalan

Jan. 2014 Endocrine- general. 2

Communication Between Cells

• Nervous.• Humeral

– Metabolites.– Paracrine.– Endocrine.

Jan. 2014 Endocrine- general. 3

Definition.

• Endocrine:– Gland that secretes hormones.

• Hormone:– Secreted into blood and act on distant target organs-

insuilin, thyroxine, etc.• Conventional endocrine glands are pancreas,

thyroid, parathyroid, pituitary, adrenal and gonads.

• Liver, heart, lymphnodes and many other organs are now known to secrete substances with distant activity.

Jan. 2014 Endocrine- general. 4

Functions of Endocrine System

• Maintaining the internal environment.• Respond to emergency demands.• Integration of growth and development.• Reproduction.• One function- several hormones.• One hormone- several functions.

Jan. 2014 Endocrine- general. 5

Neuro - Endocrine Integration.

• Neurons with endocrine function- – hypothalamus, posterior pituitary.

• Neural control of endocrine function- – Parathyroid gland.– Pancreas.

• Combined action of nervous system and endocrine system-– Maintenance of blood pressure.

Jan. 2014 Endocrine- general. 6

Regulation of Endocrine Secretion.

• Change in circulating metabolite.• Change in tropic hormone.• Nervous control.

Jan. 2014 Endocrine- general. 7

Feed Back Regulation.

metabolite.

Secretion of hormone.

Response.

Negative feed back.

+

-+

Positive Feed Back +

Jan. 2014 Endocrine- general. 8

Transport of Hormones

• Water soluble hormones are dissolved in plasma.– Peptide hormones and catecholamines.

• Fat soluible hormones are bound to proteins.– Steroids.

• Thyroxine both ways.

Jan. 2014 Endocrine- general. 9

Blood Level of Hormones.

• Increased by secretion.• Decreased by,

– Metabolic destruction by tissues.– Binding with receptors in tissues.– Excretion by liver.– Excretion by kidneys.

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Mechanism of Action of Hormones.

• Binding with specific receptors in trget cells.• The receptor brings about several changes in

the activity of the cell• Location of Receptors-

– Cell membrane- for proteins, peptides and catecholamines.

– Cytoplasm- for steroids.– Nucleus- thyroid hormones.

• Down regulation and up regulation of receptor numbers are also ways of feed back regulation.

Jan. 2014 Endocrine- general. 11

Learn About Each Hormone,

• Source.• Latent period and Half life .• Regulation of secretion and removal• Mechanism of action• Physiological actions.• Consequences of excess and

insufficiency.• Function tests and assessment.