# Why does vasodilation in periphery lead to reduction in blood pressure?

#### sameeralord

Hello everyone,

Ok generally what do they mean when they say vasodilation in periphery lead to reduction in blood pressure? Do I have to think of this as expanding the size of a fluid filled container so less fluid splashes againts the walls reducing pressure. Or do I have to think of this like a circuit where decreasing the resistane of a resistor results in decreased pressure just upstream of that resistor. Thank you

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#### Dr Lots-o'watts

Conventional blood pressure, which has become a standard vital measurement is measured around a person's arm, where vasodilatation is relevant (large arteries, smaller arterioles and large veins.)

If the arm vessels dilate, the pressure there will decrease.

http://en.wikipedia.org/wiki/Vasodilation

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#### sameeralord

Conventional blood pressure, which has become a standard vital measurement is measured around a person's arm, where vasodilatation or contraction is negligible.

If there is more room for blood in the periphery where vasodilatation occurs (the capillaries in fingers, face, organs etc), there is a little less blood in the arms (and legs and main arteries), so the measured pressure there is reduced.
Thanks a lot for the answer but here is where I'm getting confused with circuits. In a circuit if I have 2 parallel circuits, both would get the same voltage but different current depending on the resistance. So if I directly think of voltage as pressure, shouldn't the pressure be same in legs and fingers. Is this a case where the pressure and voltage analogy doesn't work. If so I understand. Thank you

#### Dr Lots-o'watts

After review, I had to make an important correction in my first post. My physiology is further than I thought.

#### Andy Resnick

Hello everyone,

Ok generally what do they mean when they say vasodilation in periphery lead to reduction in blood pressure? Do I have to think of this as expanding the size of a fluid filled container so less fluid splashes againts the walls reducing pressure. Or do I have to think of this like a circuit where decreasing the resistane of a resistor results in decreased pressure just upstream of that resistor. Thank you
There's a simplified model of blood pressure, involving the ejection volume from the heart, systemic vascular resistance, and central venous pressure:

http://en.wikipedia.org/wiki/Blood_pressure

The major driver of vascular pressure are the arterioles and capillaries. Increasing the peripheral blood flow decreases the vascular resistance, leading to a decrease in arterial pressure.

"Why does vasodilation in periphery lead to reduction in blood pressure?"

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