When the nerve impulse reaches the axon terminal, chemicals called neurotransmitters are released into the synapse. These chemicals cross the synapse and attach to receptor sites on the soma or dendrites of the next neuron. Neurotransmitters may excite the neuron, causing it to fire, or they may inhibit the neuron from firing. There are about 30 known neurotransmitters. Dopamine, adrenaline, serotonin are a few.
Nerves are bundles of neurons.
Some axons are covered with a fatty substance called myelin . Myelin helps increase the speed of nerve impulse transmission. Carries information from the body and senses to the CNS, and from the CNS to the other parts of the body. PNS is composed of the somatic nervous system and the autonomic nervous system. The somatic nervous system carries messages to and from the muscles and sense organs.