You stimulate a neuron and elicit an action potential shown

You stimulate a neuron and elicit an action potential, shown in the left graph below (the y-axis is mV). Then you foolishly leave your prep sitting out while you go grab something to cat. Meanwhile, your lab mates altered the external bath solution surrounding your cell. Fortunately, they left all of your ions untouched except for one kind. You stimulate your neuron in the exact same way you did before lunch, but you get the voltage response shown in the right graph. What ion did your lab mates mess with? Did they (raise) or (lower) the concentration of that ion?

Solution

With sodium ions. They lower the concentration of sodium ions present in the surrounding medium.

In inside of the normal cells always negative charge. During depolarization of cells Na+ ions from surrounding medium enter into the cells and makes inside positive it shows the membrane potential positive in the peak. But in the modified action potential depolarization peak is very low. It maily due to low concentration of Na+ ions in surrounding medium so, Na+ ions can\'t enter in to the cells for further depolarization.