1. 2 Functional Properties of Neurons
1. Irritability
Ability to respond to stimuli
2. Conductivity
Ability to transmit an impulse

2. How neurons communicate
Action Potential
electrical signal that travels on the membrane of a neuron
based on movements of ions between the outside and inside of the cell

3. If the stimulus reaches threshold then an action potential is started in the neuron and will travel down the membrane (This is called a nerve impulse) This is the ALL or NONE PRINCIPLE.

4. Steps to a Nerve Impulse
Polarized: Resting neuron
Inside membrane is slightly –
Outside membrane is slightly +
Most membrane channels are closed, there is some normal diffusion of K+ or Na+ between cell and the environment through the sodium/potassium pump (active transport)
Stimulus Occurs:
Depolarization: Active Neuron
Sodium (Na+) channels open allowing Na+ to diffuse into the cell quickly
This causes the inside to become + (outside -)
Repolarize: Normalizing
K+ gates open in order to allow K+ to diffuse out of the cell – this restores the membrane (+ outside, - inside)

5. Nerve Impulses Refractory Period
K+ must be moved back to the inside of the cell and NA+ must be pumped out of the cell in order to prepare for the next impulse
The sodium-potassium pump ( a membrane channel), using ATP, restores the original configuration

6. Nerve Impulses another way
Figure 7.9a–b

7. Nerve Impulses
Figure 7.9c–d

8. Nerve Impulses
Figure 7.9e–f

9. Simple Video showing Action Potential

10. Transmission of a Signal at Synapses
Impulses are able to cross the synapse to another nerve
Neurotransmitter is released from a presynaptic nerve’s axon terminal
The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter
An action potential is started in the post-synaptic dendrite

12. Name the phase and describe what is happening in each step.