Question

Select the MOST CORRECT answer. In a cardiac myocyte, changes in the permeability of ions can lead to a change in membrane potential. In...

		A conducting cardiac myocyte, the rapid depolarization is caused by the opening of T-type calcium channels.
		A contractile cardiac myocyte, the rapid depolarization is caused by the opening of L-type calcium channels.
		Both conducting and contracting cardiac myocytes, the influx of sodium and calcium cause the membrane to depolarize and the efflux of potassium causes repolarization.
		Both a) and b) are correct and c) is incorrect.
		a), b) and c) are all correct.

Select the MOST CORRECT answer. An athlete was attempting to improve their performance through doping, the act of taking illegal drugs to increase red blood cell count. Unfortunately, the athlete experienced a reduction of performance instead. Which of the following best explains this outcome?

		Heart rate and stroke volume were increased and therefore cardiac output was reduced.
		An increase in the viscosity of the blood caused total peripheral resistance to increase, which reduced blood flow.
		A decrease in mean arterial pressure resulted because of the increase in total blood volume. Because the bulk blood flow was equal between both sides of the heart, the stroke volume decreased over time.
		Both a) and b) are correct and c) is incorrect.
		a), b) and c) are all correct.

Answer 1

First one.

a), b) and c) are all correct. During the generation of a potential by the SA node the conducting cells starts to undergo depolarization due to the opening of T type calcium channels and it's transient. It takes place in the phase 4. In phase 0 the opening of L type calcium channels makes the influx of calcium and it's long lasting. But at the end in phase 3 repolarization occurs due to the efflux of potassium ions.

Second one.

An increase in the viscosity of the blood caused total peripheral resistance to increase, which reduced blood flow.

As the redblood cells increase the hematocrit also increases. As hematocrit increases the blood viscosity increases. With the increase in viscosity the total peripheral resistance increases. As a result the easy blood flow is interrupted and thereby the blood flow decreases and the athlete face a difficulty in blood supply to the body muscles and to make a better performance.