How does the Na+/K+ pump affect the ion distribution in a neuron?
Na+/K+ pumps when working give out three Na+ for taking in two K+. Lets say initially there are 10 Na+ and 10 K+ both inside and out side the membrane.
Total charge outside = +10
Total charge inside = +10
When this pump works, three Na+ are pumped out and two K+ are pumped in.
Now there are 13 Na+ are present outside and 7 Na+ inside.
Similarly, 8 K+ are present outside and 12 K+ are present inside.
Total charge outside = +21
Total charge inside = +19
The pump again pumps for the next time.
Now there are 16 Na+ are present outside and 4 Na+ inside.
Similarly, 6 K+ are present outside and 14 K+ are present inside.
Total charge outside = +22
Total charge inside = +18
So you see, the more the pump is pumping in every step the outside of the membrane is turning more positive than the inside or you can say that the inside of the membrane is turning more negative than the outside which means that there is potential difference developed across the membrane which is responsible for triggering more processes.
Ion distribution means the distribution of charge.