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9 Posts

me007
Forum Guru

Topics: 72
Posts: 803

12/13/06 - 09:01 PM

A 48 yo man desires to loose weight.His physician suggest regular phisical exercise as a way to lower heart rate, body mass index, BP and cholesterol level.
what changes (decrease-increase) will occur in
- tissue oxygen concentration
- tissue adenosine concentration
- vascular conductance
in response to exercise?

Palaniappan
Forum Senior

Topics: 30
Posts: 148

12/13/06 - 09:42 PM

Increase in tissue O2 concentration
Increase in adenosine
Inc rease in vascular conductance??

me007
Forum Guru

Topics: 72
Posts: 803

12/13/06 - 11:13 PM

right except for
decrease in tissue O2 concentration
muscle use oxygen during exercise, what reduses O2 concentration in tissues
During conditions of low oxygen in tissues adenosine level rise because oxydative phosphorilation is impaired.
adenosine is potent vasodilator - decrease arteriolar resitance- inc conductance

macTT
Forum Senior

Topics: 32
Posts: 86

12/14/06 - 02:34 AM

ME007,
If you can.....care to answer this question?
During exercise, in a normal human being.....Does stroke volume increase or decrease
? I was thinking decrease because there is less time for venous filling and due to increase heart rate. However, USMLE World says that stroke volume increases due to increase venous return from vasoconstrictive action on the veins. Hope you could clarfiy this if possible. Thx
JACK

me007
Forum Guru

Topics: 72
Posts: 803

12/14/06 - 10:31 AM

during exercise we have vasodilation in muscles due to increase blood flow to the muscle.(dilate arteries)

And vasoconstrictive action on the veins due to increase sympathetic stimulation (alfa-1 receptor - contraction)

This is creates that downstream pressure which increases venous return.

Heart rate increases and increases force of contraction (symp stim - beta-1 receptors in heart) and with incresed venous return it will increase stroke volume.

I think so.
looks right?

Palaniappan
Forum Senior

Topics: 30
Posts: 148

12/14/06 - 11:15 AM

Thanks for your explanation.If you can,It would be of much use to me if you could list dowm 8 to ten points -what are the important concepts which we must have in mind while approaching a exercise and haemorrhage question...or is there any book which gives a concise information-(except for kaplan)

macTT
Forum Senior

Topics: 32
Posts: 86

12/14/06 - 06:08 PM

me007 wrote:
during exercise we have vasodilation in muscles due to increase blood flow to the muscle.(dilate arteries)

And vasoconstrictive action on the veins due to increase sympathetic stimulation (alfa-1 receptor - contraction)

This is creates that downstream pressure which increases venous return.

Heart rate increases and increases force of contraction (symp stim - beta-1 receptors in heart) and with incresed venous return it will increase stroke volume.

I think so.
looks right?

ME,
your explanation makes sense however, I am just curious, if you have increase in heart rate during exercise (how come your SV still increase? Since you have less time filling and more time pumping. I just don't get this little part) Hope you can explain it if possible.
JACK

me007
Forum Guru

Topics: 72
Posts: 803

12/14/06 - 06:38 PM

ok, let see
http://btc.montana.edu/olympics/physiology/cf06.h...

or from here

http://bjsm.bmj.com/cgi/content/full/39/4/190

...For endurance trained subjects, the proposed mechanisms for the progressive increase in stroke volume to VO2max (maximal oxygen consumption) are enhanced diastolic filling, enhanced contractility, larger blood volume, and decreased cardiac afterload. For untrained subjects, it has been proposed that continued increases in stroke volume may result from a naturally occurring high blood volume.

or this one

http://home.hia.no/~stephens/hrttrn.htm

or just this
exercise -> inc o2 consumption +inc venous return = inc in CO

macTT
Forum Senior

Topics: 32
Posts: 86

12/14/06 - 07:56 PM

Thx bro for the clarification and the explanation......really appreaciate it sticking out tongue

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