Motor or Sensory Nerves?

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By: Thomas Cowan, M.D.

Perhaps one of Rudolf Steiner's most controversial statements in the field of science and medicine is that there is no difference between motor and sensory nerves and that, in fact, all nerves are sensory nerves.

In my upcoming book Fourfold Healing, I go so far as to say that this controversial statement is key to the understanding and treatment of all neurological diseases confronting us today. So, how can we make sense out of these words of Rudolf Steiner?

A basic concept taught to all doctors and scientists who study mammalian nervous systems, is that the peripheral nervous system is divided into two distinct components. The first, the motor nerves (also called neurons) run from the spinal column to the muscles. The second, sensory nerves, run in the opposite direction, that is, from the periphery (muscles) to the central nervous system situated in the spine. The functions of these two types of nerve are considered completely opposite even though anatomically identical.

The function of motor nerves, it is believed, is to carry impulses from brain to muscle for movement to occur. The important point here is that the direction of the signal is toward the periphery. This means that the origin of movement is in the brain, not where Steiner puts it, in the will forces.

Sensory nerves, the thinking goes, carry signals from the periphery to the brain, informing the nervous system about such things as temperature, or painful sensations. Steiner's view, however, is that all nerves are sensory nerves, and that even in the case of movement, it is the will forces that move the muscles. The brain merely senses movement. It can never initiate it.

Modern science tries to prove a distinction between sensory and motor nerves by the proven fact that movement can actually be produced in the brain and central nervous system. If you tap on your knee in the correct spot your lower leg will contract. Many similar examples seem to prove that the direction of the impulses in these motor (movement) nerves is indeed from the center to the periphery. Steiner counters by saying that such artificial experiments in no way reflect what actually happens in the human being and that, specifically, the part of the brain that seems to initiate the movement actually just senses the movement initiated by the will forces.

After years of pondering this question, I conclude that there is no way to definitively settle this issue by looking at such contrived experiments. They lead us away from looking at the real issue, which is Steiner's threefold concept of the human being and the role the nervous system plays in our lives.

In anthroposophical terms, the nerve-sense pole is the part of our threefold organization responsible for the perception of the outer world. As such, it is an essentially passive collector of information. The soul force that this nerve-sense pole brings to bear is thinking which, according to Steiner, is another example of perception, rather than activity. That is; when our nervous system functions properly we can perceive clear and true thoughts minus any distortion. Anyone can perceive the laws of mathematics. These thoughts are not independent creations but perceptions of truths that exist in the world. To think clearly, we must learn to perceive accurately, and not let our own feelings or doings get in the way.

In contrast, the metabolic-limb system is an active soul force whereby we impress our own nature on the world. I move, shape the earth, plant a garden, or create art with the forces of my limbs, under the guidance of my ego. With these will forces I make my mark on the world. This the nerve-sense pole never does. It perceives, thereby giving us information about the world around us, and information even about our own movements.

Goethe, who argued for a similar view of the nervous system, claims that the light determines the shape, form and function of the eye. It is in this statement that we begin to see the link between Steiner's conception of the nervous system as a perceiving "organ" and various neurological diseases. As Goethe says, the quality of the world we perceive determines the quality or health of the various sense organs. If we are continually exposed to abnormal light sources, such as computer or TV light waves, in time the organ of perception of light will grow weak and ill. If we continually are exposed to artificial and chemical flavorings, our ability to perceive tastes will atrophy, and living in a culture that is replete with distorted, untrue thoughts, isn't it any wonder that many people have lost the sense for truth?

Steiner and Goethe teach us that the health of the nervous system lies primarily in what it is exposed to. To put it another way, all illnesses of the nervous system are environmentally caused. Modern science has even pointed this out in some instances such as the connection between various agricultural products and deterioration of the nervous system. The therapy of neurological problems therefore must include surrounding oneself with that which is beautiful and true: food that is real, live rather than electronic music, and perhaps most importantly, people and ideas that ring of truth, not the distortions and lies that are the usual daily fare of modern life. Our nervous system integrates all that we are exposed to, and all that we do. It feeds these images down to our heart, and out of these precepts we fashion our lives on earth.

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