Since you have selected to begin as a physician or therapist, it will be assumed that you have some background in anatomy and physiology. However, through experience, I've found much of it is often left at school and not thought about aster entering practice. For that reason I will begin with a few basic concepts to remind you of some of what you learned.
A nerve is unique in that it is LONG! Looking at it in cross section it appears the same size as most other nerves, but looking at it from the side, it can be as much as 3 feet long. Nerves are the carriers of signals to and from the brain where all sensation and the majority of body control is done. The length of a nerve is determined by its origination and destination. Whether going to or from the brain the length is about the same. A sensation nerve in the big toe actually starts there and runs the entire length to the spine where it connects with a second nerve in the sequence that runs from the spinal entrance to the brain where it connects with a third nerve going to the brain area dealing with that nerves function. Control nerves do essentially the same thing, but in reverse.
Because of the way a nerve functions, any stimulation along it's full path, causes the electrical signal to continue at full force to it's end. This is the principle behind the "Phantom Limb" phenomenon and electrical stimulation of muscles in therapy and rehab. This concept becomes extremely important to understand in pain and dysfunction management.
According to Dr. Arthur Guyton, one of the world's leading experts and authors on Medical Physiology several keys must be considered;
Taken together, these direct one to understand, that if a body part, even an internal organ, is injured or dysfunctional and in pain, the muscles touching or associated with that body part will go into an involuntary contraction to prevent further injury. If that muscle cell, group of cells or the entire muscle remains in that involuntary contraction it can become self sustaining even if the original cause is eliminated. Once the group of cells enter this state, even Dr. Guyton doesn't know why it will remain long after the body part has been healed.
The only statement I will make at this point before turning
you over to further experts is
All too often we treat the symptom.
Just as often we treat the cause.
Seldom do we treat the combined picture of the patient presentation.
Thereafter, you may browse to your hearts content.