Skeletal Muscle – Structure Function Judith （骨骼肌- Judith结构函数）.pdfVIP

Skeletal Muscle – Structure Function. Learning Objectives. At the end of this course, you should be able to : 1. describe the structure of skeletal muscle 2. understand the function of a motor unit 3. give a basic description of the mechanism of muscle contraction 4. discuss the main sources of energy for skeletal muscle 5. know the difference between isometric and isotonic muscle contraction. Structure. Skeletal muscle, as the name suggests, is usually associated with the skeletal system. It is also called striated muscle because of the presence of alternating dark and light bands along the length of its fibres, or voluntary muscle because it is subject to voluntary control (although involuntary, reflex contractions and spontaneous, automatic movements also occur). nuclei Connective endomysium separates cells Mature skeletal muscle cells are long and slender; they range from 10 to 60 micrometers in diameter and may extend from one end of a muscle to the other, in some cases reaching a length of as great as 30cm. Since their length is much greater than their width, these cells are called fibres. Each muscle fibre is multinucleated and is surrounded by an electrically polarized membrane - the sarcolemma . The nuclei are usually located just under the sarcolemma. The entire muscle consists of a number of bundles of muscle fibres known as fasciculi. Surrounding each fibre and filling in the space between fibres within a fasciculus is a delicate connective tissue called the endomysium. Each fasciculus is bounded by a stronger connective tissue sheath, the perimysium, which in turn is continuous with a tough connective tissue, the epimysium, enveloping the whole muscle. The superficial fascia (subcutaneous adipose tissue) forms a