What changes occur in the circulatory system when a person stands up from a prone position?

Question

How does if affect the heart rate and blood pressure of an individual?

Answer 1

If you're standing up, you have to resist gravity more. Since there only one major source of force for blood flow (the heart), it's going to have to work harder, and probably faster. Since it's pushing on the blood more to counter gravity, the pressure is increased.

If your body doesn't compensate fast enough, blood stops going to your brain temporarily and you feel dizzy. Even as it is, there are lots of other tricks your body uses to fight gravity such as one-way valves and muscle motion which only work in their normal position, so that's also why blood rushes to your head (and eventually kills you) if you're up-side-down, but not while you're right-side-up.

Interesting stuff! Hope that helps!