| Briefly, the cardiac myofibrils are composed of the major contractile proteins, actin and myosin. |
| Within the sarcoplasm of each individual muscle fibre are approximately 1,000 to 2,000 myofibrils. |
| Within the sarcolemma is the sarcoplasm, containing all the usual subcellular elements plus long prominent myofibrils. |
| Each cell contains smaller fibres known as myofibrils that house highly organized contractile units called sarcomeres. |
| Composed of the contractile proteins actin and myosin, the myofibrils represent the smallest units of contraction in living muscle. |
| Fast-acting muscles have highly ordered structure due to the closely interrelated disposition of membranes and myofibrils. |
