as mentioned above, is there any compensatory mechanisms may be activated by the body to compensate for the abnormal high blood pressure due to hypertension?
just to double confirm with all on what exactly is this question is asking about.
in my opinion, i feel that the qn is asking us what can do the body do to bring down the abnormal high blood pressure to normal blood pressure which is directly related to how the body can decrease the afterload, rather than asking what can the body do to increase the preload.
by the way, does a rise in preload will in turn lead to a rise in afterload also? i feel that if the preload is increased by stimulation of the symphathetic system, resulting in a higher blood pressure than before. the cardiac muscle's contractility is increased thus allowing the heart to pump at a higher blood pressure rather than decreasing it.
please correct me if im wrong as im not really sure whether increase in preload will lead to increase in blood pressure. and im also not really sure what does that qn wants.
p.s: since high blood pressure is due to narrowing of our main arteries so is there any mechanism that is able to vasodilate the arteries so that the afterload is decreased thus reducing the high blood pressure?
really appreciate some help here. thanks in advance!! :wink2:
Last edit by shallowtrix on Oct 14, '06
: Reason: correction on spelling
Oct 14, '06
This can help you guide, look thru baroreceptors for quick sense and response, and as far as the question about the preload if it can increase blood pressure, you can start with this formula and then should be able to extrapolate an answer. SV x HR = CO
Oct 14, '06
The renin- angiotensin- aldosterone system, baroreceptors as mentioned, ADH, capillary fluid shift. Does that help?
Oct 15, '06
thanks all for your replies. I managed to find info on the baroreflex mechanism.
But i can't find any regarding capillary fluid shift and renin- angiotensin- aldosterone system. Is there any good websites on these 2 mechanisms?
Thanks alot once again.
Oct 15, '06
Quote from shallowtrix
thanks all for your replies. i managed to find info on the baroreflex mechanism.
but i can't find any regarding capillary fluid shift and renin- angiotensin- aldosterone system. is there any good websites on these 2 mechanisms?
thanks alot once again.
check out some fluid & electrolytes "made easy" textbooks.
the adh and renin-angiotension-aldosterone mechanisms should also be in any med surg textbooks in the f&e chapters.
Oct 15, '06
I dont think F&E easy is very good with the renin system.
look for info on the ANP/ANF
I think it goes like this, the atrial natriuretic(sp?) Factor is where it starts, the ANF causes vasodialation, decreases tubular reabsorbtion of sodium, reduces serum renin, reduces aldosterone secretions, decreases ADH.
so >ANF vasodialates to lower BP
>ANF pushes off sodium to lower BP
>ANF reduces renin which stops aldosterone. the aldosterone holds water and sodium so if it is reduced you will get a dc of sodium and water (also an elevation of K+) to lower BP
>ANF decreased ADH which will cause you to pee off the water in excess of sodium, but as long as the PT stays hydrated it will eventually lower sodium levels.
now the trick is to remember that these systems also work independentaly of ANF so you can have abnorman funstions of all of the systems, they dont nessicirally have to do what they are susposed to.
fluid shifts are more compicated and can be caused by a nubmer of factors. I learded them best by starting with the acid base balances and going from there. it will take a while to learn the fluid shifts but once you get it, it will stick forever cause everything will make sence.
for example met alk will cause an increase in bicarb, therefore a decrease in ECF H-ions which will pull H-ions out of the ICF which will cause K+ to shift into the cells because its trying to balance things. so you get hypokalemia cause its all in the cells instead of in the ECF.
that was confusing huh? well think about the osmolarity of things, if you are hypernatrimic you will have a increased ECF Osmolality which will cause a fluid shift out of the cells to try and dilute the ECF. this will cause cell dehydration.
on the flip, if you are hyponatrimic you have a low NA level in the ECF which will make the ICF more concentrated, this will cause a fluid shift into the cells causing cell swelling, increased caranial pressure and all of that.
if you really study it will all start to make sence, like if you have hypokalemia it will cause aldosterone to stop and that will cause the body to push off water and sodium in an effort to conserve K+ this may cause hyponatremia because the body is trying so hard to hold on to the potassium that is looses all of the sodium and water.
I think that I stoped makeing sence about 5 min ago so I will shut up now.
sorry if I confused you, and sorry I cant spell.
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