Which of the following factors would increase peripheral resistance?


a. Increased blood viscosity
b. Shorter vessel
c. Vasodilation
d. An increase in vessel radius

Verified step by step guidance

1. Understand that peripheral resistance is the resistance to blood flow in the circulatory system, primarily influenced by the diameter of blood vessels, blood viscosity, and the total length of the blood vessels.
2. Recall that increased blood viscosity (thickness of the blood) leads to higher peripheral resistance because thicker blood flows less easily through vessels.
3. Consider the effect of vessel length: longer vessels increase resistance, while shorter vessels decrease it.
4. Recognize that vasodilation, which is the widening of blood vessels, decreases peripheral resistance by allowing blood to flow more easily.
5. Note that an increase in vessel radius (which is a result of vasodilation) also decreases peripheral resistance, as resistance is inversely proportional to the fourth power of the radius according to Poiseuille's law.

Key Concepts

Peripheral Resistance

Peripheral resistance refers to the resistance to blood flow in the small blood vessels, primarily arterioles. It is a crucial factor in determining blood pressure and is influenced by the diameter of the blood vessels, blood viscosity, and the overall length of the vascular system. Increased peripheral resistance can lead to higher blood pressure and is a key consideration in cardiovascular health.

Blood Viscosity

Blood viscosity is a measure of the thickness and stickiness of blood, which affects how easily it flows through the vessels. Higher viscosity means that the blood is thicker, which increases resistance to flow and, consequently, peripheral resistance. Factors such as dehydration or increased red blood cell count can elevate blood viscosity, impacting overall circulation.

Vessel Radius

The radius of a blood vessel significantly influences peripheral resistance, as described by Poiseuille's law. A smaller radius increases resistance, while a larger radius decreases it. Vasodilation (widening of blood vessels) reduces resistance and lowers blood pressure, whereas vasoconstriction (narrowing of blood vessels) increases resistance and can elevate blood pressure.