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Daily Archives: November 27, 2011

Clinical Disorders of the Motor System

By |November 27, 2011|Diagnosis, Editorial|

Clinical Disorders and the Motor System

The Chiro.Org Blog

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 9 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 9:   Clinical Disorders and the Motor System


Such clinical features as fatigue, weakness, nervousness, pain, tenderness, paralysis, sensory loss, paresthesia, and abnormalities of muscle mass or tone are the most common signs and symptoms noted in neural disorders. Fatigue, weakness, and nervousness are frequently presented together. This triune can usually be attributed to a functional disorder or appear as a complication in organic disease.

Abnormal striated muscle function has its origin in diseases of the brain, spinal cord, peripheral nerves, or muscle tissue itself. Dysfunction occurs in a variety of symptoms and signs such as:

(1) impaired movements,
(2) spontaneous movements,
(3) coordination defects,
(4) abnormal reflexes,
(5) distortions of muscle tone, and
(6) postural and movement distortions.

Weakness, wasting, and sometimes paralysis are represented in these conditions. Common types of motor lesions are shown in Table 9.1.

Basic Neuromuscular Activities

There are two fundamental types of neuromuscular activity. One type consists of reflex postural contractions, which are the basis of posture and physical attitudes and maintain muscle tone. The other type consists of phasic contractions, which produce movement. Phasic contractions may be either reflex or volitional in origin. While reflex actions are always purposeful, predictable, and involuntary, cortical activity is not.

Neurons carrying phasic and tonic impulses have distinctive characteristics. Phasic motor neurons are large, have a rapid conduction velocity, have a high threshold of physiologic excitability, present large impulses of short duration, and are electrically silent during rest. In contrast, tonic motor neurons are smaller, have a slower conduction velocity, have a lower threshold of physiologic excitability, present smaller impulses of longer duration, and are electrically active during rest.

Muscle and Joint Correlations