An action potential is brought about by a sudden membrane impermiability the movement of negatively-charged proteins throught the plasma membrane. Multiple sclerosis is caused by a common soil bacteria and can be prevented by vaccination. Many axons make up a nerve. Many nerves make up an axon. Many axons make up a myelin sheath.
Many myelin sheaths make up a dendrite.
All neurotransmitters have an excitatory effect. Neuromodulators can magnify or reduce the effects of neurotransmitters. All neurotransmitters are reabsorbed intact from the synaptic cleft. Neurotransmitters diffuse across the plasma membrane of the post-synaptic cell. Synaptic potentials may vary in magnitude.