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
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