General Principles of Clinical Neurology
General Principles of Clinical Neurology
We would all like to thank Dr. Richard C. Schafer, DC, PhD, FICC for his lifetime commitment to the profession. In the future we will continue to add materials from RC’s copyrighted books for your use.
This is Chapter 2 from RC’s best-selling book:
“Basic Principles of Chiropractic Neuroscience”
These materials are provided as a service to our profession. There is no charge for individuals to copy and file these materials. However, they cannot be sold or used in any group or commercial venture without written permission from ACAPress.
Chapter 2: General Principles of Clinical Neurology
The nervous system and the endocrine system work as partners to provide the majority of functional control for body processes. Guyton, the renowned physiologist, describes the basic function of the nervous system to be the controlling factor for rapid activities such are necessary for muscle contraction, rapidly changing visceral events, and the rate of endocrine secretions.
The dominant action of the nervous system over the physical processes of the body is called neurarchy. In contrast to the nervous system, the endocrine system principally regulates the metabolic functions of the body and controls prolonged physiologic activities.
The demanding role of the nervous system of the human body can be appreciated by recognizing that during every minute of life the nervous system must receive thousands of signals from a countless variety of sensory organs, integrate the data, prepare necessary responses, and effect the responses via a multitude of motor and/or autonomic efferent mechanisms. Thus, a specialized network of nerve tissue permeates the body in such a manner that some parts receive and respond to stimuli from the external or internal environments, some parts transmit signals to and from integrating and coordinating centers, and some parts conduct messages from centers peripherally to muscles, vessels, or glands to effect an action.
As an aid in understanding the structural roles involved, physiologists McNaught/Callander portray the general design of the body as consisting of synchronized master tissues and vegetative systems. The quick-acting master tissues specialize in receiving messages from the external and internal environments and reacting to them (eg, nerve and muscle tissues).
Specialized peripheral receptors such as the telereceptors and contact receptors are impressed by stimuli from the external environment, while deep proprioceptors in muscles and joints and the interoceptors and chemoreceptors of the viscera are impressed by stimuli arising within the internal environment.
The slower-acting vegetative systems (eg, digestive, respiratory, circulatory, excretory systems) provide the basic utilities of life necessary for cellular nutrition, growth, or repair and the removal of waste products. These systems are largely regulated by the sympathetic and parasympathetic divisions of the autonomic nervous system, whose activities are modified, balanced, and integrated by centers within the central nervous system (CNS) to meet the constantly changing needs of the body.
The Evolution of Neurologic Theory
The early roots of neurology in the history of health science are extremely cloudy, but bits and pieces have been found by historians and reported by Singer, Majno, and others.
During the 4th century BC, Plato believed that health disturbances were the effect of disturbed basic elements within the body, which he labeled air, earth, fire, and water. Aristotle taught that the center of sensations of the body was within the heart. He believed that the heart received ripples from the periphery and referred them through blood vessels.
Although the School of Hippocrates later placed the center of consciousness in the brain, the subject remained controversial until the 3rd century BC when teachers at the learning center of Alexandria distinguished nerves from tendons and blood vessels, and some motor and sensory functions within peripheral nerves were established.
The early Greeks taught that nerve functions were accomplished by the movement of “humors” within the body, and this belief prevailed until the 17th century in most Western countries. Claudium Galen, in the 2nd century AD, accepted the general principles established at Alexandria and added knowledge about the spinal cord that was so detailed it remained unchanged until the 19th century. Galen was also the first to teach the proper positions and relationships of the vertebrae to the spinal column and the significance of the pulse and the arteries.
During the 19th century, physiologists began applying the new knowledge of electricity to neural function and muscle contraction, and action potentials were established in nerves and muscles in the 1800s. Most of the data collected at this time were manifestations following severed nerves. Schwann described nerve fibers and cells in 1839, but the segmental structure of nerve fibers and demyelination processes were not defined by Ranvier until the 1870s.
The all-or-nothing principle of neuromuscular excitability was not firmly established until 1871 by Bowditch for heart muscle, until 1909 by Lucas for skeletal muscle, and until 1922 by Adrian/Forbes for nerves. It should be pointed out that D. D. Palmer established the basic principles of chiropractic in the 1890s, in the middle of these rudimentary findings.
With the development of the vacuum tube in the 1920s, neurologic data expanded rapidly because measurements could be made in millisecond and microvolt ranges. The modern views of the relationship between neural structure and function were established during the period between 1900 and 1920, as were concepts of chemical actions at the junctions between excitable cells, but the compound action potential of nerve tissue was not proved until 1937. The ionic basis of the action potential in single nerve fibers was established in 1952. With the development of the electron microscope during the 1950s, the investigation of intricate neurologic morphology began.
Most of the facts proved during this century evolved from theories established many decades before. In reviewing the history of neuroscience, it is amazing to see how often the speculations of scientists with disciplined imaginations, who had to base their theories primarily on empiric experiences, proved quite accurate once technology advanced to the point where their hypotheses could be proved.
The science of chiropractic is no exception to this pattern. The lack of theoretical explanations has never been a problem. The challenge has been to formulate hypotheses in such a manner that they can be tested and to develop the means to do so under controlled conditions.
|Review the complete Chapter (including sketches and Tables)|
at the ACAPress website