The adrenal medulla, which constitutes 28%

of the mass of the adrenal gland, is made up

of interlacing cords of densely innervated

granule-containing cells that abut on venous

sinuses

Made of chromaffin cells – 2 types

Contains granules - 2 types

Paraganglia cells

The adrenal medulla is in effect a

sympathetic ganglion

The cells secrete when stimulated by the

preganglionic nerve fibers

Innervated by splanchnic nerves

prepare the body for emergencies, the "fight-

or-flight" responses

Adrenalin (epinephrine)

Noradrenalin (norepinephrine)

Dopamine

Fight or flight reactions

Pre-ganglionic ativation

Exo-cytosis of granules mediated by ca

influx

Physiological and psychological stimuli such

Pain , anxiety , trauma , hypovolemia ,

hypoglycemia , hypothermia, severe

exercise , emotional stimulus

Table 1. Classification of Adrenergic Hormone

Receptors

Receptor AgonistsSecond

MessengerG protein

alpha1 (1) E>NE IP3/Ca2+; DAG Gq

alpha2 (2) NE>E cyclic AMP Gi

beta1 (1) E=NE cyclic AMP Gs

beta2 (2) E>>NE cyclic AMP Gs

E = epinephrine; NE = norepinephrine

Alpha adrenergic receptors - NE ,E – major stimulatory (except intestine)

Beta adrenergic receptors - E – major inhibitory ( except myocardium)

Alpha 1 , 2

Beta 1, 2 ,3

Up regulation

Down regulation

Adrenalin – alpha 1,2 . Beta 1, 2 ,3

Nor-adr – alpha 1,2 . Beta 1 , poor beta

activity

Metabolism –o2 consumption co2 production

Carbohydrate Metabolism

Gluconeogenesis , glycogenolysis , glycogenesis , insulin inhibition , glucagon secretion , ACTH secretion

Lipid Metabolism – lipolysis thro’ HSL

Heart - beta 1

Cns – alertness , anxiety , tremors - beta

Blood vessel – blood pressure

Respiration – beta 2

Skin –arrector pili

Urinary Bladder And GIT

Eyes –alpha - pupilary dilation , beta produces relaxation of ciliary muscle

Blood – increases rbc , coagulability

Skeletal muscle – contraction , increase blood supply , glycogeneolysis

Smooth muscle - splenic capsule

shpincters

dilator pupillae

uterus

arrector pili

Relaxation in non sphicteric gi muscles

Urinary bladder

Bronchioles

Kidney – renin secretion

Sweat glands

Lacrmal glands

Salaivary glands

Insulin , somatostatin

Glucagon

Thyroxin , t4 – t3 enhancement

TRH

Renin secretion

Acute sympathetic stimulation

Chronic sympathetic stimulation

ACTH – increases enzymes of catechol

Cortisol - PNMT

Epinephrine

Exposure to cold

Hypoglycemia

Produced by adrenal medulla and

dopaminergic neurons

Vasoconstriction

Dilatation in mesentery

Increase in heart rate and BP

Endocrine hypertension

Anxiety

Chest pain

Fever

Headache

Hyperglycemia

Nausea and vomiting

Polyuria , glucosuria

Palpitations

Sweating

Tachycardia

Wt loss

Test for pheochromocytoma