Download MBBS Physiology Presentations 11 Adrenal Medullary Hormones Lecture Notes

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Adrenal Medul ary Hormones

Secretions of the gland

Catecholamines:

Epinephrine
Nor-epinephrine
Dopamine

Adrenal medulla is a sympathetic ganglion in

which the post ganglionic neurons have lost

their axons and become secretory cells
Catecholamines

PNMT is found in brain and adrenal medulla

Adrenal PNMT is induced by glucocorticoids

After hypophysectomy, epinephrine

concentration decreases

In 21 -hydroxylase deficiency adrenal

medulla is dysplastic
Catecholamines

95% dopamine and 70% Nor-epinephrine

and epinephrine is conjugated to sulfate

On standing the levels of free nor-

epinephrine increases by 50-100%

After adrenalectomy, plasma nor-

epinephrine levels remain unchanged but

free epinephrine level falls
Catecholamines are stored in granules with

ATP

Granules also contain chromogranin A,

opioid peptides

Adrenomedullin is also found
Regulation of catecholamines

Reduced in sleep
Increased in emergency situations
W.B.Cannon called it " The emergency

function of sympathoadrenal system"

Drugs
NE is increased by emotional stresses with

which the individual is familiar

Epinephrine rises in stresses due to

unexpected situation

Effects of Catecholamines

Increases glycogenolysis in liver and

skeletal muscles

Increases insulin and glucagon secretion by

- adrenergic mechanisms

Decreases insulin and glucagon secretion

by - adrenergic mechanisms

Increases FFA mobilization
Increases plasma lactates
Stimulates metabolic rate
Effects of Catecholamines

NE and Epinephrine both increase rate and

force of myocardial contraction

Increases myocardial excitability
Can lead to extrasystoles and arrythmias
NE produces vasoconstriction
Epinephrine causes vasodilatation
Effects of Catecholamines

Catecholamines increase alertness
Increases metabolic rate due to

vasoconstriction and lactate oxidation

When injected increases potassium levels

and later decreases

Dopamine causes renal and mesenteric

vasodilatation

Elsewhere DA causes vasoconstriction
DA has positive inotropic effect on heart
DA is useful in treatment of shock