Which of the following substances is the determinant of an individual's skin color?

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.

A. Calcium plays a critical role in blood clotting. It is involved in the coagulation cascade and is necessary for the activation of clotting factors that help stop bleeding.

B. Calcium is not involved in acid buffering. This function is primarily carried out by buffers such as bicarbonate in the blood.

C. While calcium does help regulate some functions of cells and tissues, it does not primarily contribute to extracellular osmotic pressure; this is more a function of proteins and other ions.

D. ATP production mainly occurs in mitochondria and is driven by the metabolism of glucose and fatty acids, not by calcium directly. Calcium does, however, play a role in cellular processes like muscle contraction.