1. The Nerve Impulse

2. How are electricity and nerves different?

3. Electrochemical Impulse, Pages 418-425
- Current travels along a wire much faster than the nerve impulse travels along a nerve.
- Electrical wires rely on external energy to push electrons along. Nerve Impulses rely on cellular energy (from what source?) to generate current.
-1900, Julius Bernstein, “Nerve impulses are electrochemical messages created by the movement of ions through the nerve cell membrane.”
- 1939, more evidence for the theory, action potential observed in a giant axon of a squid.

4. How do nerve cells become charged?
- neurons have a rich supply of + and - ions
- the electrochemical event is caused by an unequal concentration of positive ions across the nerve cell membrane.

5. -in the resting membrane excess + ions accumulate along the outside of the membrane, while excess - ions accumulate along the inside of the membrane, The membrane is polarized.
- this separation of charges gives the nerve cell membrane the potential to do work.
-upon excitation, the nerve cell membrane becomes more permeable to sodium than potassium. Sodium gates open!
- potassium gates close, sodium diffuses into the nerve cell. The rapid inflow of Na ions causes more + ions than - ions on the inside of the cell. The cell is now depolarized.
- K ions move out of the cell and restore polarity. The Na-K pump moves the K ions back inside and Na ions outside and the membrane is repolarized.

6. Lets have a look at the nerve impulse.

7. The Action Potential

8. The Synapse