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NBME 15 Answers

nbme15/Block 4/Question#11 (7.5 difficulty score)
A 45-year-old man comes to the physician for ...
Venous return: decreased; Carotid sinus baroreceptor activity: decreased; Cerebral blood flow: decreasedπŸ”
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 +1 
submitted by iceberglettuce(10),

The question stem describes a man with presumed orthostatic hypotension. HCTZ is associated with this condition (by causing a relative hypovolemia), and his symptoms of feeling faint when sitting up too quickly also match nicely.

When he stands, gravity causes a redistribution of blood to his legs, causing decreased venous return.

Orthostatic hypotension is defined by an inadequate baroreceptor response, hence decreased baroreceptor activity.

Lastly, we know his cerebral blood flow is decreased if he is feeling dizzy.

Helpful image: http://calgaryguide.ucalgary.ca/wp-content/uploads/2015/10/Orthostatic-Hypotension-Pathogenesis-and-clinical-findings.png

trazobone  I got stuck between increased vs. decreased baroreceptor activity. So my takeaway from this is that the baroreceptor activity will decrease regardless since there is a decrease in venous return. Key emphasis is in inadequate baroreceptor response. So activity decreases but not enough to compensate because venous return is severely decreased, hence the orthostatic hypotension. +