ABSTRACT
Study objectives Discuss the functions of skeletal muscle Distinguish between origin and insertion; exion and extension; and agonist, antagonist, and synergist muscles Distinguish between isometric and isotonic contractions Distinguish between concentric and eccentric contractions Describe the components of the thick laments and the thin laments Explain the functions of the following: myosin cross-bridges, troponin, tropomyosin, sarcomeres, Z lines, neuromuscular junction, transverse tubules, and sarcoplasmic reticulum Describe the Sliding Filament Theory of skeletal muscle contraction Explain how creatine phosphate, oxidative phosphorylation, and glycolysis provide energy for skeletal muscle contraction List the factors that inuence the onset of muscle fatigue Describe the factors that lead to the development of muscle fatigue Describe the metabolic processes that lead to oxygen debt Distinguish between the three types of muscle bers: slow-twitch oxidative, fast-twitch oxidative, and fast-twitch glycolytic Explain how the percentage of a muscle ber type in a given muscle is determined Describe the factors that inuence the strength of skeletal muscle contraction, including multiple motor unit summation, asynchronous motor unit summation, frequency of nerve stimulation, the length-tension relationship, and the diameter of the muscle ber
2. Introduction Skeletal muscle composes the largest group of tissues in the human body and accounts for up to 40% of the total body weight. This type of muscle, which is innervated by the somatic nervous system, is under voluntary control. Skeletal muscle performs many important functions in the body, including:
Movement of body parts Heat production Respiration Vocalization
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Most skeletal muscles are attached to bones, which enables them to control body movements, such as walking, making facial expressions, chewing, and swallowing. These muscles are also responsible for the manipulation of objects, such as writing with a pencil or eating with a fork. Furthermore, movement of the eyes is carried out by several pairs of skeletal muscles. Finally, the contractions of certain groups of muscles, referred to as “antigravity” muscles, are needed to maintain posture and provide body support.
