Causes of Change in TPR
Peripheral resistance increases due to binding of norepinephrine and epinephrine to the α1 receptor on vascular smooth muscles. These hormones cause vasoconstriction, thus decreasing the radius of the vessels in the periphery. Resistance is inversely proportional to radius to the power of four. Thus, a decreased radius will greatly increase the resistance.
Peripheral Resistance is also affected by the viscosity of the blood flowing through it. The viscosity of blood is normally associated with its osmolarity.
Peripheral Resistance is also dependent upon the capacitance of the blood vessel through which the blood travels.
A decrease in TPR (e.g., during exercising) will result in an increased flow to tissues and an increased venous flow back to the heart. An increased TPR will decrease flow to tissues and decrease venous flow back to the heart.
TPR also decreases in immersion of water.
Read more about this topic: Total Peripheral Resistance
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