1. How the Plasma membrane (PM) Prepares to Send an Impulse
Resting Membrane Potential:
A neuron that is not stimulated, therefore not transmitting a signal is said to be at its resting potential. The inside of the neuron is negatively charged relative to the outside.

2. Fluid is found both inside (intracellular) and outside (extracellular) of the neuron (nerve cell).
There are charged particles in the fluid. The positively charged particles are the ions Na+ and K+. The negatively charged particles are comprised of the CL- ion and large negatively charged proteins.

4. How Does the PM Send the Impulse?
Action Potential:
An action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls.
Action potentials are also known as "nerve impulses" or "spikes“.
They allow neurons to participate in cell-to-cell communication.
Action potentials are generated by special ion channels embedded in a cell's plasma membrane

5. There are two stages of an Action Potential:
1) Depolarization
2) Repolarization

6. Stages of Depolarization
Neurotransmitters stimulate the membrane of the nerve!!!
!!!!!!!!!!!!!!!
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+

7. 2) The membrane becomes 5000 times more permeable to the Na+ and Na+
rushes in.
3) This causes a sudden loss of the greater negative ion concentration state.
The inside of the neuron is now positively charged relative to the outside.
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
[+] >> [-]

8. Stages of Repolarization
1) The membrane closes it’s sodium gates.
2) The membrane opens it’s potassium gates and potassium rushes out.
3) The normal higher negative ion concentration inside the cell is re-
established.
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+ K+
[-] >> [+]

9. 4) The sodium-potassium pump moves 3Na+ out of the cell for every 2K+ in
that moves in, re-establishing the Resting Membrane Potential.
2K+
3Na+

10. 5. The depolarization and repolarization on one spot on the membrane of the neuron causes the depolarization of the adjacent areas causing the impulse to travel the length of the axon.

11. Graphing Membrane Potential
Resting Membrane Potential – neuron is not stimulated.
Depolarizing Phase – Na+ channels open.
Repolarizing Phase - Na+ channels close and K+ channels open.
Undershoot - K+ channels remain open & cannot respond to new stimuli.