Question
Fall in diastolic blood pressure due to the loss of sympathetic outflow is mediated by which receptor?
| A. |
Alpha-1 receptor
|
| B. |
Beta-1 receptor
|
| C. |
Beta-2 receptor
|
| D. |
Alpha-2 receptor
|
Show Answer
|
Correct Answer » A
Explanation
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Clinical Reasoning for the Correct Answer
– Sympathetic outflow maintains peripheral vascular tone primarily through alpha-1 receptor–mediated vasoconstriction.
– Loss of sympathetic activity leads to decreased stimulation of alpha-1 receptors → vascular smooth muscle relaxation → vasodilation.
– Vasodilation reduces systemic vascular resistance → fall in diastolic blood pressure, since diastolic BP depends largely on vascular tone.
– Beta-1 receptor activity primarily affects cardiac output, altering systolic rather than diastolic pressure.
– Beta-2 receptor activation causes vasodilation but is less relevant to resting sympathetic tone in peripheral resistance vessels.
– Alpha-2 receptor loss would increase norepinephrine release; its role in BP fall due to sympathetic loss is minimal.
Why Option A is Correct (Alpha-1 receptor):
– Mediates vasoconstriction in arterioles maintaining diastolic BP.
– Loss of alpha-1 receptor stimulation → vasodilation → decreases diastolic BP.
