Download MBBS Physiology Presentations 9 Mech Of Hormone Actn Lecture Notes

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Hormones bind with specific receptors to exert

their actions

Receptors may be present :

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1. On the cell membrane
2. In the cytoplasm
3. In the nucleus

Earl. W. Sutherland received Nobel prize for his

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discoveries on mechanism of hormone action in

1971.
Receptors

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Hormone-receptor complex binds activates a

series of signal generating mechanisms via
cascade of enzymatic reactions

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Signal molecules increase in each step leading

to manifold increase in the action ? Signal
amplification

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Peptide and amine hormones bind to cell

surface receptors

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Steroid

and thyroid hormones bind to

intracellular receptor

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Mutation of receptors causes diseases

1. Familial hypothyroidism due to mutation

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of TSH receptors

2. Color blindness due to mutation of

receptors for cone pigment

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3. Nephrogenic diabetes insipidus due to

mutation of V2 vasopressin receptors
Quantity and sensitivity of receptors

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Regulated by the hormone concentrations

1. Up-regulation
2. Down ? regulation

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3. Desensitization

Types of receptors

Ion channel linked receptors

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G-protein coupled receptors

Enzyme linked receptors
G-proteins

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Small G ?Proteins:
1. Rab family
2. Rac Family
3. Ras Family

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Large G-proteins:
Gs, Gi, Gq, Gt and G13

S.NO. Hormones using receptor

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tyrosine kinase signaling

1

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Fibroblast growth factor

2

Growth hormone

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3

Hepatocyte growth factor

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4

Insulin

5

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Insulin like growth factor

6

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Leptin

7

Prolactin

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8

Vascular endothelial growth factor
S.NO.

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Hormones using adenylyl cyclase ?Camp
messenger system

1

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ACTH

2

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Angiotensin II

3

Calcitonin

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4

Catecholamines ( receptors)

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5

CRH

6

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FSH, LH

7

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Glucagon

8

HCG

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9

PTH

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10

Secretin

11

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Somatostain

12

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TSH

13

Vasopressin (V2 receptor)

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S.NO. Hormones using Phospholipase -

C second messenger system

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1

Angiotensin II

2

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Catecholamines ( receptors)

3

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GnRH

4

GHRH

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5

Oxytocin

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6

TRH

7

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Vasopressin (V1 receptor)