2. Resting Membrane potentialResting Membrane potential  At rest, all cells are negatively charged  On inside with respect to charge on exterior

3. Resting Membrane PotentialResting Membrane Potential  The negative charge is the result of an unequal distribution of charged ions across the cell membrane

4. Resting Membrane PotentialResting Membrane Potential  A neuron is said to be polarized  This electrical charge difference is called the resting membrane potential  potential is just another way of saying “charge difference”

5. Resting Membrane PotentialResting Membrane Potential  How is this resting potential of neurons maintained?  Sodium/potassium pumps  Use energy from ATP to maintain intra/extracellular concentrations by pumping sodium out and potassium into the cell.

6. Resting Membrane PotentialResting Membrane Potential  Pumps not only maintain concentration gradients to maintain resting membrane potential,  The actually generate it by exchanging 3 sodium ions for every 2 potassium ions

7. Action PotentialsAction Potentials  How and when is a neural message generated?  A stimulus of significant strength reaches the neuron and opens sodium gates  This allows sodium ions to diffuse into the neuron, making the inside more and more positive

8. Action PotentialsAction Potentials  When this depolarization reaches a critical value called “threshold”…  Sodium gates open wide and an action potential is formed.