physiology questions

[jcosler2357]

hello, med students

i have a few questions related to the cardiovascular system

1. why would there be an increased parasympathetic tone in extrinsic response if there is an increase in preload?
2. why would there be an increased sympathetic tone in extrinsic response if there is a decrease in afterload?
3. why would there be an increased sympathetic tone in extrinsic response if there is a decrease in heart contractility?

thank you so much.
j

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[91Bravo]

I guess we're unpaid tutors now.

 

[joedoctor]

#1 and 2 are both results of a beta carotine deficiency. I'm not completely sure about number 3, but it has something to do with sodium ion channels of the heart.

 

[Blake]

hello, med students

i have a few questions related to the cardiovascular system

1. why would there be an increased parasympathetic tone in extrinsic response if there is an increase in preload?
2. why would there be an increased sympathetic tone in extrinsic response if there is a decrease in afterload?
3. why would there be an increased sympathetic tone in extrinsic response if there is a decrease in heart contractility?

thank you so much.
j

Not 100 % sure :

1) Increased preload = increased stroke volume = a determinant in blood pressure (BP) = increase in BP = stimulation of parasympathic tone to decrease BP.

2) Decreased afterload = decreased BP = stimulation of sympathic tone to increase BP.

3) Decreased contractility = decreased stroke volume = a determinant in blood pressure (BP) = decrease in BP = stimulation of sympathic tone to increase BP.

 

[Iwy Em Hotep]

Like most things in the body, the CV system runs on checks and balances to make sure your body is getting the right amount of blood to function.

If you dump in a bunch of the blood into the heart, the body's response is: "Crap, we can't pump this like usual. We'll stroke out. Let's lower the pressure."

On the other hand, if your afterload is low, your body says: "WTF is going on!? We need more blood *STAT*!" And your sympathetic system is subsequently activated to raise your BP.

At least this is how I think of things.