What are sarcomeres? (5)

Repeating contractile units which are made of myofilaments, actin and myosin myosin is thick and binds to regions on actin (thin) movement of the 2 filaments, causes the lengthening and shortening of the sarcomere Myosin has small heads which bind to regions on actin A sarcomere has a protein disc called Z line on both sides which holds the myofilaments in place