ABSTRACT
This chapter describes the membrane systems of the muscle fiber that carry excitatory signals from the nerve axon to the interior of the muscle cell. It discusses how changes in stretched rubber bands during contraction, led to the discovery of the molecular mechanism by which muscle contracts. Vertebrate skeletal muscle contracts by means of enormous multinucleated cells that evolved specifically to generate extremely rapid, repetitive, and forceful movements. The cytoplasm of the giant cells is crammed full of a highly organized, almost crystalline, array of cytoskeletal filaments whose only function is to produce contractile force. One of the most astonishing discoveries about skeletal muscle in recent years is that it contains a second system of protein filaments. Made of the proteins titin and nebulin, these filaments are left behind with the insoluble residue after other muscle proteins have been extracted.
