Difference between Potential of action & Na+/K+ pump?

Question

Hey i would like to know the differences between these 2 things, i cant figure it out from Google....

Answer 1

Hi, Interested P.

For a moment focus on the word "potential", what does it mean? What is a "potential" for action. Imagine an object raised above the Earth's surface, it has "potential" because it's subject to Earth's gravitational force and therefore, can do something interesting when dropped into water causing a wave. Similarly an object traveling through space, having momentum, has energy to do something interesting (potential) if it were to collide with another object. Light traveling from the Sun onto a solar panel can generate electricity, as photons traveling at the speed of light have the "potential" for action (energy).

Now, it's should be easier to understand the difference of outside the cell and inside the cell, due to separation by cell's plasma membrane, creating a "potential" difference and ability for action to do something interesting. In this case, we are thinking about neurons generating an action potential (an electrical impulse) that will travel like a wave through axons to the brain. In other words, peripheral neurons in a finder, which are exposed to pain stimulus, will generate an action potential (electrical wave) that will travel through axons to the brain, conveying that pain information to the brain. The generation of this action potential occurs due to opening of sodium channels in plasma membrane, allowing (+) Sodium ions to enter the inside of the cell, causing depolarization (initiation of action potential or think of an electrical impulse). However, once the Sodium ions have entered the cell, the potential difference between the outside of the cell & inside the cell has been lost and must be restored to generate another action potential, this is analogous to recharging of phone battery. For this purpose, plasma membrane has Na/K ATPase channels that will actively pump out 3 Sodium ions in exchange for 2 Potassium ions, restoring the membrane potential or repolarization.

Of course you may wonder about the fact that Potassium ions are also (+) ions, so how would this Na/K exchange achieve repolarization of the plasma membrane potential? A very good question. The answer is in the understanding the difference between a chemical gradient and an electrical gradient. In our blood, the normal amount of sodium is tightly controlled by our kidneys to be between 135 to 145 milliequivalents per liter (mEg/L), which is far greater than normal Potassium level of 3.6 to 5.2 mEg/L. In other words, pumping out of Sodium ions has a far greater impact on restoring the electrochemical gradient across the plasma membrane.

I hope this answer is helpful but please let me know if you have more questions.

Answer 2

Hi! An action potential is just a rapid change in charge (or voltage) across our cell membranes. Action potentials allow signals to pass through. For example, if I touch a very hot stove, the pain message in my brain travels through neurons and generates an action potential which allows my body to recognize I am in pain. Action potentials are also known as the cells "depolarizing."

The Na+/K+ pump is a system of facilitated diffusion, meaning that it is a protein that helps ions with charges diffuse across the membrane. It will pump 3 sodium out from the inside of the cell membrane and it will pump 2 potassium in from the outside of the cell membrane.

In a resting state, there are more Na+ ions on the outside of the cell membrane and more K+ ions on the inside of the cell membrane. When an action potential occurs, these ions diffuse across the membrane and create that difference in charge. But, the cell cannot keep firing action potentials, this would be energy inefficient! The Na+/K+ pump returns the sodium to the outside and the potassium to the inside. The pump allows the cell to return to rest. This is called "repolarizing."

I hope this helps! Please let me know if you have any other questions or would like something clarified!