Nothing can replace the hands-on experience of isolating muscles. By tracing them from
their point of origin to their insertion a better understanding of their function can be gained.
This brief tutorial is intended to reinforce what can more easily be learned working with an actual rat. Think
of muscles in terms of antagonistic (opposite) actions. When one muscle of an antagonistic pair contracts its antagonist
will relax. Also keep in mind that several muscles may have similar actions and that the exact movement of a bone
will be the result of a coordinated effort involving many muscles. In these simplified diagrams, arrows
indicate the direction in which the force is exerted. Follow the links provided
under the different types of joints for illustrations of how the muscles interact with the skeletal elements.
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Flex - a motion that decreases the angle between two
bones. An example of a flexor is the biceps brachii. Extend - a motion that increases the angle between two bones. An example of an extensor is the triceps brachii. |
Hinge Joints |
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Protract - a motion that moves a bone parallel
to the longitudinal axis and in an anterior direction. Retract - a motion that moves a bone parallel to the longitudinal axis and in a posterior direction. |
Ball & Socket Joints |
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Adduct -Moving a
skeletal element toward the ventral midline. Abduct - Moving a skeletal element away from the ventral midline. |
