If we were able to artificially alter the membrane permeability of pacemaker cells so that sodium influx is more rapid, a. heart rate would decrease, but blood pressure would rise due to the excess sodium present b. tetanic contraction would occur due to the short absolute refractory period of cardiac muscle c. threshold is reached more quickly and heart rate would increase d. potassium channels compensate and no change in heart rate would occur

The correct answer is option C. threshold is reached more quickly and the heart rate would increase.

Explanation:

The natural pacemaker or cardiac pacemaker is the aggregations of cells that create electrical impulses that set the pace of blood pumping. The electrical impulses or the action potential are responsible for the contraction of the cardiac muscles. The rate of cardiac muscles is term as heart rate, which is control by the impulse or action potentials regulated by sodium influx and potassium outflux.

Thus, the correct answer is option C. threshold is reached more quickly and the heart rate would increase.

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