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Old 08-10-2012
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Vascular Vasoconstrictive Response to Severe Blood Loss!

A 22-year-old college student suffers multiple fractures and internal abdominal injuries in an automobile accident, accompanied by severe blood loss into the peritoneal cavity that reduces his mean arterial pressure below 50 mm Hg and decreases cardiac output. What sympathetic vasoconstrictor response will most likely occur in this patient?

a) Central nervous system (CNS) ischemic reflex
b) Increased atrial natriuretic peptide (ANP) secretion
c) Pressure natriuresis
d) Renal/body fluid mechanism
e) Valsalva maneuver
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Old 08-10-2012
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?Dd...Renin angiotensin aldosterone system
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Old 08-10-2012
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a) Central nervous system (CNS) ischemic reflex
massive vasoconstriction as a result of ischemia of vasomotor center raising B.P to levels as high as the heart can pump against
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Old 08-11-2012
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d) Renal/body fluid mechanism or a) cns ischemic response
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Old 08-16-2012
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b), c) and e) reduce Pressure, so no

d) is not clearly Sympathetic, it says "fluid" mechanism,

So I'm going with

a) Central nervous system (CNS) ischemic reflex
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Old 08-16-2012
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i'll go with A casandra watz the answer.....???
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Old 08-16-2012
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A

renal is for long term control not immediate
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Old 08-17-2012
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Default correct answer :)

The answer is a) Central nervous system (CNS) ischemic reflex

A decrease in arterial pressure below 50 mm Hg would likely cause cerebral ischemia, eliciting the very powerful CNS ischemic reflex that increases efferent sympathetic stimulation to the heart and vessels.

As for D - The renal/body fluid mechanism is an important regulator of mean arterial pressure, but it is a slowly acting system that would not be effective in an acute situation such as that described.
Plus I don't think R-A-A works anymore when the mean arterial pressure is below 50 mm Hg.
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Old 08-18-2012
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Quote:
Originally Posted by Casandra View Post
Plus I don't think R-A-A works anymore when the mean arterial pressure is below 50 mm Hg.
Why do you think so?
I think it does, but as you said it's not an immediate response to hemorrhage...
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