1. Electrochemical Gradient Causing an Action Potential
Understand the basic processes in the transmission of an action potential.

2. What is an Action Potential?
Nerve impulse or “signal”
Signal that is passed from one neuron to another

3. Videos of Action Potential
1. Resources/Movies/vasynapt.mov
2. Resources/Movies/vaaction.mov

4. Important Ions Cation = positive ion Ex: K+, Na+, Ca++
Anion = negative ion
Ex: Cl-
K+ = Potassium
Na+ = Sodium
Ca++ = Calcium
Cl- = chloride

5. Membrane Potential
Caused when opposite charges are separated by a cell membrane and want to move to balance each other out.
More cations on outside of cell than inside of cell so you have a membrane potential

6. Electrode measures membrane potential of a nueron
Axon

7. Phases of Membrane Potential
1. Resting potential: –70mV (inside of axon more negative than outside)
2. Depolarization: 0 to +30 mV (inside of axon more negative than outside)
3. Repolarization: +30 back to –70mV (inside of axon becoming more negative than outside)
4. Hyperpolarization: -70 mV to –100mV (inside axon way more negative than outside)

8. Phases of Membrane Potential
Hyperpolar-ization

9. Basic Steps to an Excitatory Action Potential
1. Neuron is at resting potential (-70 mV)
2. Neurotransmitters bind to receptors on dendrites
3. Causes Na+ to rush into cell body
4. Membrane potential becomes more positive +30mV
5. Na+ channels close
6. K+ rushes out of cell to balance out differences in membrane potential

10. Basic Steps to an Excitatory Action Potential (continued)
7. Membrane potential goes back to -90mV but then goes back to -70mV
8. Continues along length of axon
9. Action Potential reaches axon terminal and Ca2+ channel open
10. Ca2+ enters axon terminal and binds to vesicles
11. Vesicles with NT inside travel to end of axon terminal
12. Vesicles release NTs into synaptic cleft
13. NT’s travel through synaptic cleft and bind to next neuron

11. Copyright Pearson Prentice Hall
The Nerve Impulse
An impulse begins when a neuron is stimulated by another neuron. At the leading edge of an action potential, gates in the sodium channels open, allowing Na+ ions to flow into the cell. This flow of ions causes the action potential to move.
Copyright Pearson Prentice Hall

12. Copyright Pearson Prentice Hall
The Nerve Impulse
An impulse begins when a neuron is stimulated by another neuron. At the leading edge of an action potential, gates in the sodium channels open, allowing Na+ ions to flow into the cell. This flow of ions causes the action potential to move.
Copyright Pearson Prentice Hall

13. Copyright Pearson Prentice Hall
The Nerve Impulse
At the trailing edge of an action potential, gates in the potassium channels open, allowing positive ions to flow out and restoring the resting potential of the neuron.
Copyright Pearson Prentice Hall

14. Copyright Pearson Prentice Hall
The Synapse
Synaptic cleft
Copyright Pearson Prentice Hall