How going from laying to standing affects arterial blood pre

How going from laying to standing affects arterial blood pressure in the head region?

Solution

When we are laying,the Mean Arterial Pressure(MAP) is at the same level of the heart which is about 100 mm Hg. When we try to stand up from the lying position,our head is placed above our heart and gravity starts to pull the blood back downwards to our heart and feet.Return of venous blood is reduced and this leads to a decrease in cardiac stroke volume and decline in mean arterial pressure which is reduced to 60-70 mm Hg.This decreases the flow of blood to head.In response to this reduction in arterial blood pressure in the brain,parasympathetic nervous system is withdrawn and sympathetic nervous system is activated to pump more blood to head region via increased heart rates.

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