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24 Cards in this Set
- Front
- Back
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Norepi, Epi and Dopamnme are excreted by the adrenal medulla. TRUE/FALSE
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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.
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How is Norepi formed?
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By hydroxylation and decarboxylation of tyrosine, and epinephrine by methylation or norepinephrine.
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What is the enzyme that catalyzes the formation of epi from norepi?
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Phenyletahnolamine-N-methyltransferase(PNMT). It is found in the brain and adrenal medulla. It is induced by glucocoticoids.
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Glucocorticoids are necessary for the normal development of the adrenal medulla. TRUE/FALSE
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TRUE. In 21B-hydroxylase deficiency, glucocorticoid secretion is reduced during fetal life and the adrenal medulla is dysplastic.
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In plasma, about 95% of the dopamine and 70% of the norepi and epi are conjugated to sulfate. TRUE/FALSE
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TRUE.
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Regarding free epinephrine, is their a difference in plasma levels between recumbent and non recumbent the level increases 50-1005 folsubjects?
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Yes. In recumbent patients, the normal plasma levels is about 300pg/ml. On standing the level increases 50-100%.
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What are intrinsic cardiac adrenergic cells?
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These cells contain epi and norepi and account for app. 15% of the total catecholamine content of the heart.
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What is the plasma free dopamine level?
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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.
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The catecholamines have a half life of about 2 minutes in the circulation. TRUE/FALSE
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TRUE.
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How is norepi and epi stored?
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In the medulla. They are stored in granules with ATP. These granules also contain chromagranin A.
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How is catecholamine secretion initiated?
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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.
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Epinephrine containing cells of the medulla also have and secrete opioid peptides. TRUE/FALSE
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TRUE.
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What is the precursor molecule?
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Preproenkephalin. Most of the circulating metenkephalin comes from the adrenal medulla.
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What are some of the metabolic effects of norepi and epi?
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Glycogenolysis in liver and skeletal muscle, mobilization of FFa, increased plasma lactate and stimulation of the metabolic rate.
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The effects of norepi and epi are brought about by actions on two classes of receptors. What are they?
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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.
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Norepi and epi both increase the force and rate of contraction of the heart. TRUE/FALSE
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TRUE. These are mediated by B1 receptors. They also increase myocardial excitability causing extrasystoles.
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Does Norepi produce vasoconstriction?
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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.
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What happens when norepinephrine is infused slowly in normal animals and humans?
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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.
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How does epi and norepi produce glycogenolysis?
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They produce this effect via Beta adrenergic receptors that increase cAMP with activation of phosphorylase, and via alpha adrenergic receptors that increase intracellular Ca+.
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Does epi and norepi cause an initial rise in plasma K+?
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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.
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Epinephrine produces tachycardia when the plasma level is about 50pg/ml, ie, about twice the resting value. TRUE/FALSE
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TRUE.
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What is a pheochromacytoma?
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It is a adrenal medullary tumor, that secretes norepi or epi and produces sustained hypertension.
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What is the effect of injected Dopamine?
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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.
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Where is Dopamine made?
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It is made in the renal cortex. It causes natriuresis and may exert this effect by inhibiting renal Na+-K+ ATPase.
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