quansar
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can anybody explain the plot ?? I thought the solid line is already for maximal dilation thus anything above it should not be possible.
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| me007
Forum Guru
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what number nbme it is?
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| quansar
Forum Newbie
Topics: 6
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or sorry I missed the 4 in the title. it is form4
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| Luckyall
Forum Guru
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we had a big discussion on this Qs posted by laura81 i guess... look for it , i think it was about 5-6 weeks back 
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| Luckyall
Forum Guru
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answer is x--------> z
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| quansar
Forum Newbie
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I found the post.
But still I do not think I got it. Luckyall, it seems you know well of this topic. may I ask couple more question:
1. what does perfusion pressure mean in this q, is that diastolic blood pressure??? at starting point X, the perfusion pressure seems quite low, < 60 mmHg, which can not be a normal diastolic pressure. correct??
2. In the q stem it says the solid line represents maximal dilation, then at Z, the diameter of the vessel should still be the same, right???
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| quansar
Forum Newbie
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I wonder why X is the point for resting state heart?? is it true that at resting state the coronary blood vessel is maximally dilated??
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| me007
Forum Guru
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the only resonable choices x-z or x-y (lowest possible perfusion pressure at start)
blood flow will incr more bcs of local factors - hypoxia and adenosine
perfusion pressure not incr as much bcs of tachicardia
so, c.
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| quansar
Forum Newbie
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THANK, I think I am getting it
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| lq2006
Forum Elite
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X----->Z
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| pr20
Forum Senior
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could it not be Y----W.
x cannot be the starting point as it indicates a maximally dilated heart at rest.
Z cannot be possible as it is more than the highest blood flow for the given perfusion pressure at maximal dilation.
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| 1moremonth
Forum Newbie
Topics: 4
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Sorry that I am pulling this up from the dead...but I couldn't get my picture to upload correctly...........so on this question I also thought D: Y-->W.
The rationale being--
it has to be either C or D because if you start running, the idea is that your coronary blood flow has to get significantly larger, right (eliminating B)?
I am just confused about answer C--can you HAVE a valid point (Z) above the line, since the line represents the point at which coronary vessels are ALREADY maximally dilated? It seems to me that you just CAN'T have a point at Z--it goes beyond the limits defined by the question.
It seems to me that D would be a better answer, since that would mean a person has a normal diastolic pressure of 80, and when he starts running, the diastolic pressure goes up to like 130 (ok, which is a bit high I know.... but still....)
Any help appreciated!!
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| Dr.dheeraj25
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The answer should b Y to W....in the question the first part says when the coronary artery is fully dilated that was the line plotted to determine the relatioship...So when the artery if fully dilated the blood pressure falls so the perfusion pressure is low 58mm of hg....
and the myocardium recieves blood durin diastole it is the perfusion pressure is diastolic blood pressure
Next part says in a healthy individual ....in a healthy individual the DBP is 80 and when he starts running the coronary blood flw increases and also the DBP so the point on the graph which represents this is W....so its Y to W
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| Ablation
Forum Newbie
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I'm going for Y to W too. Under the same perfusiion pressure, how could the coronary flow possibly be higher than when it's maximally dilated? Also, while at rest the sympathetic nervous system is tonically active on blood vessels so the coronary arteries cannot be fully dilated(hence it shouldn't start from point X.
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| abdalla
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CCCC sure don't over think of it
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| madoo
Forum Senior
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abdalla wrote:CCCC sure don't over think of it
could u plz explain why ?
___________________
denial,anger,bargining,depression     thank allah and go straight to acceptance
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| drgbolls
Forum Junior
Topics: 13
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the answer is C check this out
http://www.cvphysiology.com/Hemodynamics/H001.htm
or page 101 on kaplan physiology 2004 edition.
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| doctorpassword
Forum Newbie
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I checked. The answer must be Y-> Z.
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| aesoig
Forum Newbie
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Yeah The answer is obviously C (x->z). There is no reason to pay attention to the fact that its beyond the determined flow in the maximally dilated artery. I also agree that it must be Y-->Z.
I think its also amusing that they list V, but don't have any answers with V.
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| blackhawk
Forum Newbie
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guys this a an easy one. I got a simple explanation for everyone! The qs gives a big hint saying the dark line is the line of max dilation of the CA's. So the resistance cannot fall beyond this point ie point X. So Z goes out of question. So we must deal with all points to the right of the solid line. We have points W, Y and V. No at rest there will be some perfusion pressure (PP) and some resistance (R) also. Besides there will be a baseline flow (Q). we must use the eqn Q=dP/R. So when at rest we can be at points Y or V. As we exercise body tries to increase flow due to metabolism and adenosine formation causing dilation of CA's so R will fall. but we have to atleast maintain a normal perfusion pressure unless heart is in a pathological state. So to maintain a constant dP body will reduce the R or in other words the point moves upwards to go towards our solid line ie towards point Z. Now we have 2 options either V to Z or W to Z. the options do not give V to Z so it has to be W to Z which is also tallying with the actual normal values approximately. Hope everyone got it!
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