1. THE NERVE

2. Nerve Function & The Nervous System
The nerve is the functional component of the nervous system that conveys information about stimuli in the environment throughout the body
The nervous system is designed for environmental responses requiring speed

3. Nerve Structure
Input Zone contains the dendrites and cell body which receive the stimulus
Trigger Zone where threshold must be met for further conduction of the stimulus
Conduction Zone composed of the axon that carries the stimulus
Output Zone composed of axon endings that convey the stimulus.

4. Nerve Structure

5. Resting Membrane Potential
When not being stimulated nerve cells have a large quantity of sodium ions (Na+) on the outside and a large quantity of potassium ions (K+) on the inside
Overall, there is a slight positive charge on the outside of the cell (-70mV)

6. Membrane Channels
Membrane channels are responsible for the balance of sodium and potassium ions inside and outside the cell
Normal Channels, Voltage Sensitive Channels, and the Sodium/Potassium Pump are involved

7. Nerve Impulse: Before Stimulation
The sodium/potassium pump ejects 3 sodium ions for every 2 potassium ions that enter maintaining the resting membrane potential
Other channels are inactive

8. Nerve Impulse: Stimulation
Stimulation of a nerve cell causes voltage sensitive sodium channels to open allowing sodium ions to pass into the cell
This causes a reversal of charges
If Threshold (-40mV) is met then adjacent sodium channels open as well

9. Nerve Impulse: Unidirectional
When the membrane potential meets it maximum value (+30mV), voltage sensitive potassium gates open allow K+ to move outside the cell returning the cell to it resting potential
Sodium voltage sensitive gate begin to close.

10. Nerve Impulse: After Stimulation
To return the membrane potential fully, the sodium/potassium pump continues to eject sodium and take in potassium

11. Changes in Potential

12. Communication Between Nerves
Once the stimulus reaches the axon endings, vesicles containing neurotransmitters merge with the membrane and release their contents into the synapse between nerves cells
Receptors on the postsynaptic cell bond the neurotransmitter