1. Nerve Impulses

2. The neuron membrane Three major types of embedded proteins
Sodium (Na+) gated channels
Potassium (K+) gated channels
Sodium-Potassium Pump
Gated channels opened/closed based on conditions, allow facilitated diffusion when open
Pumps – use ATP to do active transport (move against the concentration gradient

3. IV. Nerve Impulses A. Resting potential – at rest, the neuron cell membrane is polarized (more positive outside than inside) to -70mV

4. Depolarization – a stimulus depolarizes the membrane allowing Na+ into the cell.
1. If the impulse is strong enough (reaches the threshold) an Action Potential is generated (goes down the length of the axon)
All or none

5. Repolarization – K+ ions rush out of the cell in response to the Na+ coming in
Hyperpolarization – prevents another action potential from starting before one is finished (refractor period)

6. Return to resting potential
Sodium and potassium channels close, Na+/K+ Pump restores resting potential

9. Saltatory conduction – transmission of an impulse through myelination

10. Communication at the Synapse
Direction of impulse

11. 6

12. Action potential reaches axon terminals of pre- synaptic cell
Causes Ca2+ to enter the cell
Signals for the release of neurotransmitter into the synapse by exocytosis
Neurotransmitter diffuses across synapse, binds to receptors on post-synaptic cell
Opens sodium gates to start an action potential in the post synaptic cell