The nervous system is responsible for short-term immediate communication and control between various body systems. In contrast to the endocrine system that achieves long-term control via chemical (hormonal) mechanisms, the nervous system relies on both chemical and electrical transmission of signals and commands.

Nerve cells (neurons) are specialized so that at one end there is a flared structure termed the dendrite. At the dendrite, the neuron is able to process chemical signals from other neurons and endocrine hormones. If the signals received at the dendrite end of the neuron are of a sufficient strength, and properly timed, they are transformed into action potentials that sweep down the neural cell body (axon) from the dendrite end to the other end of the neuron, the presynaptic portion of the axon that ends at the next synapse (the extra cellular gap...