Which of the following stimulates the production of new erythrocytes?

A. Myelin is a fatty substance that wraps around axons in many neurons. It acts as an insulative covering that speeds up the transmission of nerve impulses by enabling the signal to jump between gaps in the myelin (called nodes of Ranvier). This is the correct answer.

B. The synapse is the junction between two neurons where signals are transmitted. It is not involved in the insulative covering of a neuron.

C. The axon is the long, slender part of a neuron that transmits electrical signals, but it requires myelin to efficiently conduct those signals.

D. Dendrites are branched extensions of a neuron that receive signals from other neurons. They do not have an insulative function.

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.