At the conclusion of this chapter, the student should be able
- 1. Name and describe the functions of the basic structures
of the nervous system.
- 2. Explain how gradations in strength of muscle contraction
and precision of movements occur.
- 3. Name and define the receptors important in musculoskeletal
- 4. Explain how the various receptors function, and describe
the effect each has on musculoskeletal movement.
- 5. Describe reflex action, and enumerate and differentiate
among the reflexes that affect musculoskeletal action.
- 6. Demonstrate a basic understanding of volitional movement
by describing the nature of the participation of the anatomical
structures and mechanisms involved.
- 7. Perform an analysis of the neuromuscular factors influencing
the performance of a variety of motor skills.
The role of the bones, joints, and muscles in human movement
were presented in the previous two chapters. The appropriate function
of these systems requires an intact nervous system. Therefore, this
chapter takes up the role of the nervous system in initiating, modifying,
and coordinating muscular action.
Loofbourrow (1973) presented this topic so succinctly and vividly
that his classic and still applicable introductory paragraph is
quoted here in full as an introduction to this chapter:
The forces which move the supporting framework of the
body are unleashed within skeletal muscles on receipt of signals
by way of their motor nerves. In the absence of such signals, the
muscles normally are relaxed. Movement is almost always the result
of the combined action of a group of muscles which pull in somewhat
different directions, so the control of movement involves a distribution
of signals within the central nervous system (CNS) to appropriate
motor nerves with precise timing and in appropriate number. In order
for movements to be useful in making adjustments to external situations,
it is necessary for the central nervous system to be appraised of these
situations, which are continually changing. A means of providing
this information promptly exists in a variety of receptors sensitive
to changes in temperature, light, pressure, etc. These receptors
are signal generators which dispatch signals (nerve impulses) to
the CNS over afferent nerve fibers. The CNS receives these signals
together with identical ones from within the muscles, joints, tendons,
and other body structures and is led thereby to generate and distribute
in fantastically orderly array myriads of signals to various muscles.
This, despite the enormous complexity of the machinery involved,
enables the individual to do one main thing at a time. This is integration.
It is what Sir Charles Sherrington meant by “the integrative
action of the nervous system.”
The following discussion does not presume to be an exhaustive
treatise on neuromuscular mechanisms. It attempts rather to present
as simply as possible those mechanisms that are pertinent to the
study of kinesiology. Because of techniques made possible by electronic
sensing and imaging devices, great strides have been made in acquiring
more accurate information ...