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In simple terms, a joint (where two or more bones join together) forms the axis (or fulcrum), and the muscles crossing the joint apply the force to move a weight or resistance. A first-class lever has the axis (fulcrum) located between the weight (resistance) and the force (figure 1.21a). In a third-class lever, the most common in the human body, force is applied between the resistance (weight) and the axis (fulcrum) (figure 1.23a).
In addition to the central nervous system components (brain and spinal cord), the nervous system has a peripheral component, made up of the cranial nerves, spinal nerves, and autonomic nervous system. The cranial nerves (12 pairs) (figure 10.6) and the autonomic nervous system (figure 10.7) have their origins in the cranium and are therefore closely associated with the central nervous system. Nerves conducting impulses to voluntary muscles are referred to as motor nerves; nerves conducting ...
Note that the lateral collateral ligament, unlike the medial collateral ligament, does not have fibers attaching to the lateral meniscus. In the middle of the knee joint are two ligaments known as the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) (see figures 12.10 and 12.11). Three ligaments of the knee joint are found exclusively on the posterior aspect of the joint: the oblique popliteal ligament, the arcuate ligament, and the ligament of Wrisberg (figure ...
Review the posterior muscles of the shoulder joint and the rotator cuff. Contraction of the teres minor muscle, like the infraspinatus muscle, produces external rotation and extension of the shoulder joint. This muscle is also one of the shoulder joint muscles of the rotator cuff.
