Article #1: Excerpt from Funk and Wagnalls New Encyclopedia
The following excerpt from Funk and Wagnalls New Encyclopedia, Copyright 1979 is used to illustrate the complexity of structural movement so as to give us perhaps a better appreciation of the synergism that is involved even in simple structural manipulation. Excerpted from Volume 19, pages 118-119.
The human skeleton consists of more than 200 bones bound together by tough and relatively-inelastic connective tissues called ligaments. The different parts of the body vary greatly in their degree of movement. Thus, the arm at the shoulder is freely movable, whereas the knee joint is definitely limited to a hingelike action. The movements of individual vertebrae are extremely limited, the bones composing the skull are immovable. Movements of the bones of the skeleton are affected by contractions of the skeletal muscles to which the bones are attached by tendons. These muscular contractions are controlled by the nervous system.
The nervous system has two divisions, the somatic, which allows voluntary control over skeletal muscles, and the autonomic, which is involuntary and controls cardiac and smooth muscle and glands. The autonomic nervous system has two divisions, the sympathetic and the para-sympathetic. Many, but not all, of the muscles and glands that distribute impulses to the larger interior organs possess a double nerve supply, in such cases the two divisions may exert opposing effects. Thus, the sympathetic and parasympathetic systems respectively increase and decrease heartbeat. The two nerve systems are not always antagonistic, however, for example, both nerve supplies to the salivary glands excite the cells of secretion. Furthermore, a single division of the autonomic nervous system may both excite and inhibit a single effector, as in the sympathetic supply to the blood vessels of skeletal muscle. Finally, the sweat glands, the muscles that cause involuntary erection or bristling of the hair, the smooth muscles of the spleen, and the blood vessels of the skin and skeletal muscles are actuated only by the sympathetic division.
Voluntary movement of head, limbs, and body is caused by nerve impulses arising in the motor area of the cortex of the brain and carried by cranial nerves or by those that emerge from the spinal cord to reach skeletal muscles. The reaction involves both excitation of nerve cells energizing the muscles involved and inhibition of the cells that excite opposing muscles. A nerve impulse is an electrical change within a nerve cell or fiber; it is measured in millivolts, lasts only a few milliseconds, and can be recorded.
Movement may occur also in response to an outside stimulus; thus, a tap on the knee causes a jerk, and shining a light into the eye makes the pupil contract. These involuntary responses are called reflexes. Various nerve terminals called receptors constantly send impulses into the central nervous system. These are of three classes: exteroceptors, those sensitive to pain, temperature, touch, and pressure; interoceptors, which react to changes in the internal environment; and proprioceptors, which respond to variations in movement, position and tension (especially important in doing corrective exercises. -The Authors).
These impulses terminate in special areas of the brain, as do those of special receptors concerned with sight, hearing, smell, and taste.
Muscular contractions do not always cause actual movement. Ordinarily, a small “fraction of the total number of fibers in a muscle may be contracting. (One reason why it takes prolonged periods of time to accomplish desired results—The Authors.) This serves both to maintain the posture of a limb and cause the limb to resist passive elongation or stretch. This slight continuous contraction is called muscle tone.
- 1. Introduction
- 2. What Is A Corrective Exercise?
- 3. Deformity Is Widespread
- 4. The Spine
- 5. Correct Postural Maintenance Vital To Wellness
- 6. Exercise—General
- 7. Questions & Answers
- Article #1: Excerpt from Funk and Wagnalls New Encyclopedia
- Article #2: Exercise
- Article #3: Good Posture By Dr. Herbert M. Shelton
- Article #4: Correcting Sensitivity to Light By Edwin Flatto, N.D., D.O.
- Article #5: Words Of Wisdom By Silvester Graham