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Flashcards in Alpha Blockers Deck (18)
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Alpha adrenergic receptors are mainly active where?



two types of alpha receptors are?

Alpha one and alpha two


Alpha one is where and does what?

Post-synaptic. Leads to increased intracellular Calcium by increasing the production of DAG (diacylglycerol) and IP3. Smooth muscle contraction. 1b and 1d in the vasculature, 1a in the prostate.


Alpha two

pre-synaptic, activation leads leads to decreased production of cyclic AMP and inhibits norepinephrine feedback so it keeps getting released.


What effect does an alpha blocker have on norepinephrine?

Severely lessens its effects on blood pressure. Bp does not go up.


Beta blocker on norep?

No effect


Alpha blocker on epinephrine?

Epinephrine is weird. It activates alpha receptors and beta receptors. Activation of alpha receptors obviously causes a vaso constrictive effect which raises blood pressure. Activation of Beta 2 receptors is the opposite. It creates a vasodilatory effect. SO alpha blockers block the alpha receptors but leave the beta blockers open and lead to a decrease in blood pressure because the only thing that works is the vasodialator.

Beta blockers allow epinephrine to inc blood pressure


Alpha blockers on isoproterenol

No effect on alpha receptors so alpha blockers. Beta receptors are the only things it effects so blood pressure still decreases dramatically. Beta blockers on the other hand will keep isoproterenol from decreasing BP.


Phenotolamine has an affinity for which receptors

Both alpha one and two


phenoxybenzamine has affinity for which

alpha one more than two


Terazosin, Doxazosin, Prazosin have affinity for which receptors?

Alpha one way more than 2


What can blocking alpha 1a lead to?

improving urine flow rate in BPH patients.


toxicity of the alpha blockers

orthostatic hypotension on first dose, tachycardia with blockade of alpha 2-presynaptic receptors


Phenoxybenzamine mech

alpha 1 and 2 antagonist.


Phenoxybenzamine toxicity

sinus tach, bnasal decongestion, etc...


Low doses of phentolamine do what and how?

raise BP be selectively blocking the alpha 2 receptor


High doses of phentolamine do what?

Lower BP by selectively blocking the alpha one receptor.


Contrast the effect of alpha and beta receptor blockade on epinephrine and norepinephrine induced change in BP and HR

Under normal conditions, as norepinephrine goes up, blood pressure goes up. Alpha blockers decrease this effect. Beta blockers cause Blood pressure to rise (because the alpha receptors in vasculature is still active)
In regards to epinephrine, usually as epinephrine rises, so does BP. ALpha blockers cause blood pressure to decrease drastically, beta blockers cause a rise for the same reason as above.