Question

muscles require oxygen to produce the usable energy that causes muscles to move. blood flow supplies oxygen to muscle cells during exercise. which of the following describes how exercise affects this flow of blood to the muscles? exercise results in an increased heart rate, which causes the blood flow to slow down. exercise promotes the loss of water through sweat, which causes the blood flow to speed up. exercise causes the widening of the blood vessels, which leads to an increase in the flow of blood. exercise triggers valves in the blood vessels to open, which leads to a decrease in the flow of blood.

Explanation:

• Analyze Option 1: Increased heart rate should increase blood flow (not slow down), so this is incorrect.
• Analyze Option 2: Sweating (water loss) doesn't directly cause blood flow to speed up; blood flow changes due to vascular and cardiac adaptations, so this is incorrect.
• Analyze Option 3: During exercise, blood vessels (arterioles) in muscles dilate (widen) to increase blood flow for oxygen and nutrient delivery, which matches physiological knowledge.
• Analyze Option 4: Blood vessels (except veins) don't have valves that open/close to decrease blood flow during exercise; this is incorrect.

Answer:

C. Exercise causes the widening of the blood vessels, which leads to an increase in the flow of blood.