Endocrine system basic
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Transcript of Endocrine system basic
ENDOCRINE SYSTEM
DR.NILESH KATE.M.D.
ASSOCIATE PROFESSOR,DEPARTMENT OF PHYSIOLOGY,
ESIC MEDICAL COLLEGE& HOSPITAL,GULBARGA.
OBJECTIVES
Hormone : definition, classification.
Hormones general consideration.
Hormone receptors & mechanism of action.
Measurement of hormones.
HOMEOSTASIS & CONTROLS
Successful
compensation
Homeostasis
reestablished
Failure to
compensate
Pathophysiology
○ Illness
○ Death
Figure 1-5: Homeostasis
COMPARISON OF ENDOCRINE AND NERVOUS SYSTEMS.
NERVOUS SYSTEM
“WIRED”
CHEMICAL SIGNAL AT TARGET CELL
RAPID
BRIEF DURATION CLOSE ANATOMICAL
PROXIMITY
ENDOCRINE SYSTEM
“WIRELESS”
CHEMICAL SIGNAL IN BLOOD.
SLOW
LONG DURATION
SPECIFIC RECEPTORS
ENDOCRINE SYSTEM
Hormaein-- Greek word means “to execute or to arouse”.
Def:- Secretary product of ductless glands
which are released in catalytic amounts into
blood stream & transported to specific target
cells where they elicit physiologic,
morphologic & biochemical responses.
Long Distance Communication: Endocrine Hormones
Signal Chemicals
Made in endocrine cells
Transported via blood
Receptors on target cells
Figure 6-2a: Long distance cell-to-cell communication
TYPES OF HORMONES Functional
ENDOCRINE HORMONES – Travel through the blood to act at a site distant from the secreting cell or gland
PARACRINE HORMONES – Act on cells near the secreting cell
AUTOCRINE HORMONES – Act on the secreting cell
NEUROCRINE HORMONES – Secreted by neural cells
○ neurotransmitters
○ neurohormones
Paracrine and Autocrine Hormones
Local communication
Signal chemicals diffuse to target
Example: Cytokines
Autocrine–receptor on same cell
Paracrine–neighboring cells
Figure 6-1c: Direct and local cell-to-cell communication
CHEMICAL CLASSIFICATION OF HORMONES
Depending upon chemical nature
Amines or amino acid derivatives:
Proteins & Polypeptides:
Steroid hormones
Depending upon mechanism of action.
Group I hormones.
Group II hormones. : A,B,C,D.
HORMONE : GENERAL CONSIDERATION.
Hormones chemistry, synthesis, storage & release.
1 Amines / amino acid derivatives
2 Protein & polypeptide hormones.
3 Steroid hormones.
HORMONE TRANSPOT, PLASMA CONC, HALF LIFE.
Hormone transport.
Unbound.
Bound .
Plasma concentrations.
Peptide hormone 10 -12 mol/ L to 10 -14 mol/L
Epi / Nor Epi = 2× 10-10 to 13 × 10 -10
Steroid & thyroid 10-9 mol/ L & 10-6 mol/ L.
Half life.
Peptide hormone – short
Steroid, & thyroid – long.
HORMONE DISPOSAL.
Target cell uptake & intracellular degradation.
Metabolic degradation / inactivation.
Urinary / biliary secretions.
Metabolic clearance rate (MCR):-
volume of plasma cleared per unit time.
Figure 7-14: Negative
feedback loops in the
hypothalamicanterior
pituitary pathway
NEGATIVE FEEDBACK REFLEXES : LONG , SHORT & ULTRASHORT LOOP.
HORMONES RECEPTORS.
Characteristics
Specificity .
Location .
○ Internal
○External .
Regulation of number.
○Down regulation
○Up regulation .
CLASSIFICATION OF RECEPTORS.
Receptor kinase
Receptor linked kinase.
G-protein coupled receptors.
Ligand gated ion channels.
MECHANISM OF ACTION OF HORMONES.
Through change in membrane permeability.
Through effect on gene expression.
Through second messengers.
Through tyrosine kinase activation.
THROUGH CHANGE IN MEMBRANE PERMEABILITY.
Hormones bind with external receptors.
Conformational change in protein of receptors.
Opening of Na, K, Ca channel.
Movement of ions.
THROUGH SECOND MESSENGERS SYSTEM.
Adenyl cyclase- cAMP system.
Guanyl cyclase –cGMP system.
Membrane phosplipase- phoapholipidsystem.
Calcium- calmodulin system.
MEASUREMENT OF HORMONES.
BIOASSAY. Injecting unknown sample of
plasma in experimental animals & observing specific biological effect.
IMMUNOASSAY.(AG-AB REACTION) RADIOIMMUNOASSAY
○ Mix
Unknown sample of plasma containing hormone + purified specific antibody + purified hormone tagged with radioactive isotopes.
ELISA
○ Instead of specific antibody, stained with suitable dye. & intensity of colour measured by spectrophotometer.
MEASUREMENT OF HORMONES.
CYTOCHEMICAL ASSAY.
Endocrine gland cut in slices
Incubate in ascorbateenriched culture medium
Genesis of hormone detected.
DYNAMIC TESTS.
Suppression type.
Stimulation type.
ENDOCRINE REFLEX PATHWAYS: OVERVIEW
Figure 7-9: Hormones may have multiple stimuli for their release