ENDOCRINE BASIC
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Transcript of ENDOCRINE BASIC
OBJECTIVES
Hormone : definition, classification. Hormones general consideration. Hormone receptors & mechanism of
action. Measurement of hormones.
HOMEOSTASIS & CONTROLS Successful
compensationHomeostasis
reestablished Failure to
compensatePathophysiology ○ 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 derivatives2 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/LEpi / Nor Epi = 2× 10-10 to 13 × 10 -10
Steroid & thyroid 10-9 mol/ L & 10-6 mol/ L. Half life.
Peptide hormone – shortSteroid, & 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- phoapholipid
system. 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
slicesIncubate in ascorbate
enriched 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