Question

Standing for a long time will decrease COP ?

T or F

Answer 1

False

• Gravitational forces affect cardiac output.
• On standing venous blood volumes and pressures will change.
• thus resulting gravitational force will cause the blood to accumulate in extremities.
• In legs, hence venous pressure and volume increases.
• That causes thoracic venous blood volume and central venous pressure to decrease.
• Thus, the preload is also got reduced.
• which affects the stroke volume, causing it to decrease by Frank starling mechanism.
• With reduced pulmonary venous return/ by decreased left ventricular preload, stroke volume of left ventricle also gets reduced.
• Thus reducing cardiac output - this mechanism is termed as postural hypotension.
• reduction in the cardiac output lead to decrease in the blood flow in the brain, which lead to the activation of baroreceptors
• with activation of baroreceptors they sent signal to the vsomotor centre of the brain that is medulla
• this cause withdrawal of the parasympathetic activity thus there will be increase in the heart rate
• And activation of the sympathetic neurons cause increase in the vascular resistance and cardiac contraction thus there will again increase in the heart rate
• thus increase in the heart rate lead to increase in the cardiac output inorder to cope up with the metabolic demand of various tissues
• Thus finally there will be increase in the COP