PHGY 209 Lecture : PHGY 209 Muscle physiology.doc

• School: McGill University
• Department: Physiology
• Course: PHGY 209
• Professor: Ann Wechsler

Document Summary

Skeletal muscle is used for posture and locomotion. This is the muscle that enables our arms and legs to contract, under our conscious control. Cardiac muscle is responsible for the rhythmic contractions of the heart. Smooth muscle causes involuntary contraction in blood vessels, gut, bronchi and the uterus. Thin cells constituting muscles are called muscle fibers (can be 1 ft long) Muscle is attached at each end to tendons, which in turn attach to bone on both sides of a joint. Contraction of skeletal muscle pulls on the tendons resulting in flexion of the joints. Muscle fibers are generated during development by the fusion of a large number of small precursor cells called myoblasts. Each myobast has a single nucleus, whereas the fiber is a multinucleated cell. The striations within each myofibril are caused by alternating light i-bands and dark a-bands. In the center of each light band is a dark line called the z-line.