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24 Cards in this Set

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  • Back
Norepi, Epi and Dopamnme are excreted by the adrenal medulla. TRUE/FALSE
TRUE. Cats and some other species secrete mainly norepi, but in dogs and humans, most of the catacholamine output in the adrenal vein is epinephrine.
How is Norepi formed?
By hydroxylation and decarboxylation of tyrosine, and epinephrine by methylation or norepinephrine.
What is the enzyme that catalyzes the formation of epi from norepi?
Phenyletahnolamine-N-methyltransferase(PNMT). It is found in the brain and adrenal medulla. It is induced by glucocoticoids.
Glucocorticoids are necessary for the normal development of the adrenal medulla. TRUE/FALSE
TRUE. In 21B-hydroxylase deficiency, glucocorticoid secretion is reduced during fetal life and the adrenal medulla is dysplastic.
In plasma, about 95% of the dopamine and 70% of the norepi and epi are conjugated to sulfate. TRUE/FALSE
Regarding free epinephrine, is their a difference in plasma levels between recumbent and non recumbent the level increases 50-1005 folsubjects?
Yes. In recumbent patients, the normal plasma levels is about 300pg/ml. On standing the level increases 50-100%.
What are intrinsic cardiac adrenergic cells?
These cells contain epi and norepi and account for app. 15% of the total catecholamine content of the heart.
What is the plasma free dopamine level?
About 35pg/ml and quantities of dopamine are present in the urine. Half of the plasma dopamine comes from the adrenal medulla and the rest from the sympathetic ganglia of the ANS.
The catecholamines have a half life of about 2 minutes in the circulation. TRUE/FALSE
How is norepi and epi stored?
In the medulla. They are stored in granules with ATP. These granules also contain chromagranin A.
How is catecholamine secretion initiated?
Secretion is initiated by acetylcholine released from the preganglionic neurons that innervate the neural secretory cells. The acetylcholine opens cation channels, and the Ca+ that enters the cells from the ECF triggers exocytosis.
Epinephrine containing cells of the medulla also have and secrete opioid peptides. TRUE/FALSE
What is the precursor molecule?
Preproenkephalin. Most of the circulating metenkephalin comes from the adrenal medulla.
What are some of the metabolic effects of norepi and epi?
Glycogenolysis in liver and skeletal muscle, mobilization of FFa, increased plasma lactate and stimulation of the metabolic rate.
The effects of norepi and epi are brought about by actions on two classes of receptors. What are they?
Alpha and Beta adrenergic receptors. Alpha receptors are subdivided into 2 groups; alpha 1 and alpha 2 receptors, and beta receptors into B1, B2 and B3.
Norepi and epi both increase the force and rate of contraction of the heart. TRUE/FALSE
TRUE. These are mediated by B1 receptors. They also increase myocardial excitability causing extrasystoles.
Does Norepi produce vasoconstriction?
Yes. It does so in most organs via alpha 1 receptors, but epinephrine dilates the blood vessels in skeletal muscle and the liver via B2 receptors.
What happens when norepinephrine is infused slowly in normal animals and humans?
The systolic and diastolic blood pressures rise.The hypertension stimulates the carotid and aortic baroreceptors, producing reflex bradycardia that overrrides the direct cardioacceleratory effect of norepi.
How does epi and norepi produce glycogenolysis?
They produce this effect via Beta adrenergic receptors that increase cAMP with activation of phosphorylase, and via alpha adrenergic receptors that increase intracellular Ca+.
Does epi and norepi cause an initial rise in plasma K+?
Yes. because of release of K+ from the liver and then a prolonged fall in plasma K+ because of an increased entry of K+ into skeletal muscle that is mediated by B2 adrenergic receptors.
Epinephrine produces tachycardia when the plasma level is about 50pg/ml, ie, about twice the resting value. TRUE/FALSE
What is a pheochromacytoma?
It is a adrenal medullary tumor, that secretes norepi or epi and produces sustained hypertension.
What is the effect of injected Dopamine?
It produces renal vasodilation, by acting most likely on a specific dopaminergic receptor. it also produces vasodilation in the mesentery. Elsewhere, it produces vasoconstriction by releasing norepinephrine and it has a positive inotropic effect on the heart bty an action on B1 adrenergic receptors.
Where is Dopamine made?
It is made in the renal cortex. It causes natriuresis and may exert this effect by inhibiting renal Na+-K+ ATPase.