There are currently two favored theories to explaining the effectiveness of acupuncture.
One is called the “gate control” theory and the other is called “neuro-endocrine” theory.
In the gate control theory, thin nerve fibers transmit the sensation of pain while thick nerve fibers carry the sensation of touch. It has been found through experimentation that if impulses in the thick fibers are increased, conduction in the thin fibers are selectively decreased; thus the analogy of opening and closing a gate.
By closing certain gates a method of controlling pain is introduced, which is to say that by increasing transmission in the thick fibers it reduces the impulses in the thin fibers thereby relieving pain. Acupuncture has been found to increase transmission in the thick fibers markedly.
Neuro-endocrine theory has recently been discovered in which using acupuncture to stimulate certain points along the meridians; the body itself releases its own natural painkiller called endorphins.
Endorphins are released by many parts of the nervous system and is related to the glandular or endocrine system, hence the term neuro-endocrine. Along with these two main theories, others explain the science of Acupuncture through “Augmentation of Immunity” theory, “Neurotransmitter” theory, and “Circulatory” theory.