Why does constriction of the veins helps to increase arterial pressure when blood pressure falls?

Answer 1

Easiest way to explain this is this: if you take a garden hose and run the water, the water just runs out.....put your thumb half way over the hole and the water shoots out really far!!!! So think of the hose as your vessel and if you decrease the lumen (diameter) of the hole, pressure increases!!!

i.e. the volume is greater than the container which increases pressure..... that's also why medics give IV solution.... to increase the volume inside the container (your vessels)

Answer 2

When veins constrict, you apply pressure on the blood flowing through them. thus arterial pressure increases. blood pressure increases.

Answer 3

The blood vessels constrict to the arms and legs so the major organs can receive blood.
Without blood to the brain, lungs, kidneys, etc, we die.