Myocardium, also known as cardiac muscle, is the musclar component of the heart found in the walls of the ventricles, atria and intraventricular septum. It consists of involuntary striated muscle cells that are uninucleate and are attatched to each other by specialized junctions known as intercalated disc. The disc allows a contraction of myocardium in a swinging pattern. Thus, the heart has a possibility to work as a pump. Although cardiac muscle fibers are striated, they differ from skeletal muscle cells, because they are much smaller and are not multinucleate. The intercalated dics are composed of two important components, desmosomes and gap juntions. Desmosomes are strong connections that hold neighbouring cells together. Gap junctions are related to electrical signals in the heart and allow depolarisation to spread rapidly from cell to cell.
Intercalated discs are composed of two structures: gap junctions and desmosomes which play an important role in heart contraction. Electric coupling is formed when some passages are formed by junctions gaps. Because of these channels depolarizing signal can go from one muscle cell to another. In that way, the rapid transmission of action potentials and the contraction of the heart muscle is generated.
Desmosomes are structures which hold the ends of muscle cells together. Thus, throughout the stress of fiber contraction, the cells stay together and do not separate. Pacemaker cells - special cell structures that control heart beating and heart rate. However, contraction of the heart cannot be controlled by a person, it is controlled by the autonomic nervous system which sends different signals, e.g. to increase or decrease the heart rate.
- ↑ Dee Unglaub Silverthorn, Human Physiology an intergrated approach 6th edition, page 473 and 475, Published by Pearson 2012