Question

Chytrid fungus kills frogs and is thought to contribute significantly to worldwide declinesin amphibian populations. The fungus blocks the entry of Na+ & K+ through the skin ofinfected frogs, thus reducing the extracellular concentrations of these ions. ECGrecordings show that the electrical activity of the heart becomes impaired as ion balance is disrupted, and the frogs ultimately die from cardiac arrest.

a. How would a decrease in extracellular Na+ affect the function of pacemakercells? How would it affect the function of contractile cells?

b. How would a decrease in extracellular K+ affect the function of pacemaker cells? How would it affect the function of contractile cells?

c. How would these effects contribute to cardiac arrest?