An increase in which of the following is a result of stimulation of the sympathetic nervous system?

A. During the expiratory phase of respiration, the diaphragm relaxes and moves upward, causing the chest cavity to decrease in size and forcing air out of the lungs. This is a key part of the breathing process.
B. Oxygen is not taken into the lungs during expiration. Instead, expiration is the process of expelling carbon dioxide from the lungs after oxygen has been absorbed during inspiration.
C. The diaphragm contracts during the inspiratory phase to increase the volume of the lungs and draw air in, not during expiration.
D. Oxygen is not released from the lungs during expiration; rather, carbon dioxide is expelled from the lungs as a waste product of metabolism.

A. Vasodilation refers to the widening of blood vessels, which typically lowers blood pressure by decreasing the resistance within the vessels.

B. Increased cardiac output means the heart pumps more blood per minute, which raises blood pressure by increasing the volume of blood circulating through the arteries. This is the correct answer.

C. Decreased heart rate would typically lower blood pressure, as the heart is pumping less frequently, reducing the force exerted on the blood vessels.

D. Parasympathetic stimulation generally lowers blood pressure as it promotes relaxation and reduces the heart rate, which in turn reduces cardiac output.