Information is transmitted through chemical messages called neurotransmitters, and these messages are triggered by action potentials. Every cell has a membrane voltage (difference in charge) called a membrane potential. The resting potential is the membrane potential when the neuron is not sending signals to other cells. In a human cell at resting potential, the concentration of potassium is greater inside the cell while the concentration of sodium is greater outside the cell. There are Na/K pumps inside the membrane that will transport 3 Na+ molecules outside of the cell and 2 K+ molecules into the cell. There are also many open K+ channels that allow K+ ions to flow out of the cell. Thus, the inside of the cellular membrane is negative in comparison to the positive charge outside the cell (more positive charges going out than coming in), resulting in a negative resting potential charge of about -70 mV.
An action potential is when Na+ ion channels open in response to stimuli allowing Na+ ions to flow into the cell, thus resulting in a depolarization (membrane potential becomes less negative). Once the membrane potential reaches the threshold (about -55 mV), there is a spike in membrane potential known as the action potential in which many Na+ ions are rushing into the cell. After this spike, most gated Na+ ion channels will close and K+ channels will open and the membrane potential will fall again (becoming more negative). The membrane potential will become even more negative than the resting membrane potential for a little bit (known as the undershoot, where gated K+ ion channels close) before returning back to the resting potential.
There is a refractory period in which a second activation potential cannot occur while one is already occurring because the Na+ ion channels close. Na+ ion channels will close after an activation potential passes, making sure that the activation potential travels in one direction and not backwards.
So those are the basics, sorry for the super long answer! Hope this helps. I suggest that you check out the website listed which is my professor's lecture on the membrane potentials, it includes some really nice diagrams of action potentials and neurons that help a lot. :)
An action potential is when Na+ ion channels open in response to stimuli allowing Na+ ions to flow into the cell, thus resulting in a depolarization (membrane potential becomes less negative). Once the membrane potential reaches the threshold (about -55 mV), there is a spike in membrane potential known as the action potential in which many Na+ ions are rushing into the cell. After this spike, most gated Na+ ion channels will close and K+ channels will open and the membrane potential will fall again (becoming more negative). The membrane potential will become even more negative than the resting membrane potential for a little bit (known as the undershoot, where gated K+ ion channels close) before returning back to the resting potential.
There is a refractory period in which a second activation potential cannot occur while one is already occurring because the Na+ ion channels close. Na+ ion channels will close after an activation potential passes, making sure that the activation potential travels in one direction and not backwards.
So those are the basics, sorry for the super long answer! Hope this helps. I suggest that you check out the website listed which is my professor's lecture on the membrane potentials, it includes some really nice diagrams of action potentials and neurons that help a lot. :)
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