Diastolic blood pressure __ as exercise intensity increases.
A does not change
B increases
C decreases
The correct answer and explanation is:
The correct answer is B. increases.
During exercise, blood pressure generally rises due to the increased demand for oxygen and nutrients by muscles. Systolic blood pressure (the top number) increases significantly during exercise because the heart has to pump more forcefully to meet this demand. However, diastolic blood pressure (the bottom number) behaves differently.
Diastolic pressure typically increases only slightly or stays the same during moderate-intensity exercise. However, during intense exercise, it may increase more noticeably. This increase happens because of the combination of several factors:
- Vascular Resistance: As exercise intensity increases, blood vessels supplying muscles constrict to divert blood to active muscles, increasing peripheral resistance. This contributes to a slight increase in diastolic pressure.
- Sympathetic Nervous System Activation: Exercise activates the sympathetic nervous system (part of the autonomic nervous system), which increases heart rate and the force of contraction. The increase in vascular tone (narrowing of blood vessels) leads to a rise in diastolic pressure.
- Baroreceptor Response: The body tries to maintain blood pressure stability during exercise. The baroreceptors in the carotid arteries and aorta detect changes and send signals to adjust the pressure. During higher-intensity exercise, this results in a higher diastolic reading due to the need to balance out blood flow and pressure.
- Return to Resting Levels: After exercise, diastolic pressure usually returns to normal levels fairly quickly, reflecting the reduction in vascular resistance and lower heart rate.
In conclusion, while systolic pressure rises sharply with exercise intensity, diastolic pressure generally shows a more gradual increase due to vascular changes, sympathetic activation, and other physiological responses during physical activity.