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Objectives
To review the basic anatomy and function of the muscular and nervous systems
To review and understand the basic terminology used to describe muscular locations, arrangements, characteristics and roles, as well as tissue properties and neuromuscular functions
To learn and understand the different types of muscle contraction and the factors involved in each
To learn and understand basic neuromuscular concepts in relation to how muscles function in joint movement and work together in effecting motion
To develop a basic understanding of proprioception and kinesthesis
To develop a basic understanding of the neural control mechanisms for movement
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Skeletal muscles are responsible for movement of the body and all its joints. Muscle contraction produces the force that causes joint movement in the human body but may also control and prevent movement. In addition to the function of movement, muscles also provide both dynamic stability of joints and protection, contribute to posture and support, and produce a major portion of total body heat. There are over 600 skeletal muscles, which constitute approximately 40% to 50% of body weight. Of these, there are 215 pairs of skeletal muscles. These pairs of muscles usually work in cooperation with each other to perform opposite actions at the joints they cross. In most cases, muscles work in groups rather than independently to achieve a given joint motion. This is known as aggregate muscle action.
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In attempting to learn the skeletal muscles, it is helpful to have an understanding of how they are named. Muscles are usually named because of one or more distinctive characteristics, such as their visual appearance, anatomical location, or function. Examples of skeletal muscle naming are as follows:
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Shape—deltoid, rhomboid
Size—gluteus maximus, teres minor
Number of divisions—triceps brachii
Direction of fibers—external abdominal oblique
Location—rectus femoris, palmaris longus
Points of attachment—coracobrachialis, sternocleidomastoid
Action—erector spinae, supinator, extensor digiti minimi
Action and shape—pronator quadratus
Action and size—adductor magnus
Shape and location—serratus anterior
Location and attachment—brachioradialis
Location and number of divisions—biceps femoris
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In discussions regarding the muscles, they are often grouped together for brevity of conversation and clearer understanding. The naming of muscle groups follows a similar pattern. Here are just a few muscle groups assembled according to different naming rationales:
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Shape—hamstrings
Number of divisions—quadriceps, triceps surae
Location—peroneals, abdominal, shoulder girdle
Action—hip flexors, rotator cuff
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Figs. 2.1 and 2.2 depict the muscular system from both a superficial and a deep point of view.
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