Which of the following statements correctly describes a factor that influences blood pressure?

• A. Blood pressure is unaffected by the volume of blood in the circulatory system.
• B. A decrease in heart rate always increases blood pressure.
• C. Blood viscosity has no impact on blood pressure.
• D. An increase in blood vessel diameter generally decreases blood pressure.

Answer: (D)

Verified step by step guidance

1. Understand the concept of blood pressure: Blood pressure is the force exerted by circulating blood on the walls of blood vessels. It is influenced by several factors, including blood volume, heart rate, blood viscosity, and the diameter of blood vessels.
2. Analyze the first statement: 'Blood pressure is unaffected by the volume of blood in the circulatory system.' This is incorrect because blood pressure is directly influenced by blood volume. If blood volume increases, pressure typically rises, and if blood volume decreases, pressure typically falls.
3. Evaluate the second statement: 'A decrease in heart rate always increases blood pressure.' This is incorrect because a decrease in heart rate generally reduces the amount of blood pumped by the heart per minute (cardiac output), which can lower blood pressure rather than increase it.
4. Examine the third statement: 'Blood viscosity has no impact on blood pressure.' This is incorrect because blood viscosity (thickness) affects the resistance to blood flow. Higher viscosity increases resistance, which can elevate blood pressure.
5. Assess the fourth statement: 'An increase in blood vessel diameter generally decreases blood pressure.' This is correct because when blood vessels dilate (increase in diameter), resistance to blood flow decreases, leading to a reduction in blood pressure.