The salient features of cardiac muscles; how are they different from striated muscles
The cardiac muscles are confined to the walls of heart only. They have a unique function of contracting rhythmically and continuously. They generate a unique wave excitation as they pass from one fibre to another. The cardiac muscle fibres are made up of short cylindrical fibres joined end to end. These are interconnected by crosslinks forming a network. It is this arrangement that helps in the rhythmic contraction so characteristic of the heart muscles.
The muscle fibres are uninucleate and do not have a sarcolemma. The cardiac muscle fibres are striated but the bands are much paler than those of the striated muscle fibres. The cytoplasm consists of a large number of mitocondira and numerous glycogen granules.
There are some speicalised regions of the membrane at the end of the fibres which bring about cris- cross junction – these areas are called intercalated discs (rather than Z lines of the striated muscles). These intercalated discs help as boosters of the wave action permitting the motion to be transferred from one fibre to the other. The cardiac muscles like skeletal muscles (striated muscles) contract quickly but do not experience fatigue.