Short Answer and Critical Thinking
15. Name and describe the four functional abilities of muscle that are the basis for muscle response. Contractibility- is the ability to shorten forcibly when adequately stimulated. This ability sets muscle apart from other tissue types. Extensibility- is the ability to extend or stretch. Muscle cells shorten when contracting, but they can stretch even beyond their resting length, when relaxed. Elasticity- is the ability of a muscle cell to recoil and resume its resting length after stretching. 16. Distinguish between (a) direct and indirect muscle attachments and (b) tendon and an aponeurosis. (a.) In direct or fleshy attachments, the epimysium of the muscle is fused to the periosteum of a bone or perichondrium of a cartilage. In indirect attachments, the muscle’s connective tissue wrappings extend beyond the muscle either as a ropelike tendon or as a sheet like aponeurosis. The tendon or aponeurosis anchors the muscle to the connective tissue covering of a skeletal element (bone or cartilage) or to the fascia of other muscles. (b.) a tendon is a cord of dense fibrous tissue attaching muscle to the bone, and aponeurosis is fibrous or membranous sheet connecting a muscle and the part it moves. 17. (a) Describe the structure of a sarcomere and indicate the relationship of the sarcomere to myofilaments. (b) Explain the sliding filament model of contraction using appropriately labeled diagrams of a relaxed and contracted sarcomere. (a.) The region of a myofibril between two successive Z discs is a sarcomere. It averages 2 micrometers long and is the smallest contractile unit of a muscle fiber. It contains an A band flanked by half an I band at each end. Within each myofibril, the sarcomeres align end to end like boxcars in a train. (b) In a relaxed muscle fiber, the thin and thick filaments overlap only at the ends of the A band. The sliding filament model of contraction...