Myasthenia gravis is a disease that interrupts the way nerves communicate with muscles. In order to understand this disease, you must have some understanding of how things work in the normal situation.
A neuron is a cell. It has a head called a cell body at one end, a long strand called an axon, and a foot piece with small branching fingers called foot processes. The neurons that myasthenia gravis involve have their cell bodies (their heads) in the spinal cord and their foot processes (their feet) in the voluntary muscles that we use to move our bodies (our skeletal muscles.) The spinal cord sends a message to move a certain muscle. The neuron receives this message and carries it to that muscle.
A nerve is a group of axons. The white fibrous structures we call nerves are actually groups of axons bundled together similar to the way electrical wires in your home are bundled inside an insulating cord.
Neurotransmitters are chemicals. In order for a message to be transferred between neurons, a chemical is released from the foot processes of the first neuron and is taken up by one of the branches of the receiving neuron?s head (or by the muscle.) After the chemical message has been successfully transferred, an enzyme destroys the neurotransmitter molecule in order to prevent on-going stimulation. The neurotransmitter we are concerned with in myasthenia gravis is called acetylcholine and the enzyme that degrades it is called acetylcholinesterase.
The neuromuscular junction is the area where neuron and muscle interface. There are three types of muscle: heart muscle; smooth (or involuntary) muscle, the kind that moves food through your intestine or constricts your pupils); and striated (or voluntary) muscle, with which you use to walk, type, sing, and control facial expression. It is the neuromuscular junction on the striated muscle that is stricken in myasthenia gravis.
Acetylcholinesterase breaks down acetylcholine. When acetylcholine breaks down, muscle stimulation stops.
Anticholinesterases break down acetylcholinesterase. When there is no acetylcholinesterase, there is more acetylcholine. More acetylcholine means more muscle stimulation.
And now Myasthenia Gravis
Myasthenia gravis is the condition where the neuromuscular junctions are diseased. The acetylcholine message from the nerve trying to stimulate the muscle is quickly blunted. There are several forms of myasthenia gravis.