What's this all about?

    In order to understand Lambert-Eaton Syndrome (LES), it is first necessary to have a general understanding of the nervous system. The human nervous system is composed of the central nervous system (CNS), which consists of the brain and spinal cord, and the peripheral nervous system (PNS), which includes all the neural tissue outside the CNS.  PNS is composed of two basic types of neurons (nerve cells): motor neurons and sensory neurons. Motor neurons, the target of LES, are used to send signals from the CNS to the body to stimulate a reaction. The most important of these reactions when discussing LES are muscle contractions. Sensory neurons move information the other way, from the PNS to the CNS, and bring information about the environment to the brain.
 
 

The nerve itself is composed of a cell body (called a soma), an axon, and dendrites. 


 
 
 
 
 

Nerves send signals using an electrical charge that is passed from the dendrites,to the axon, then to the next cell.  This electrical signal, known as a nerve impulse, is created by the movement of ions. Sodium (Na+) ions migrate into the nerve cell because of stimulation from the  central nervous system. This creates a net localized positive charge inside the cell, called an action potential.  However, the positive charge degrades as it moves through the cell because the ions will diffuse (and then so will the local charge). The nerve cell has devised a mechanism to keep the magnitude of the charge it receives and then later transmits at a constant value.