Heart pump blood through the heart and into the major arteries. The pacemaker cells make up 1% of cells and form the conduction system of the heart. They are generally much smaller than the contractile cells and have few myofibrils which gives them limited contractibility. Their function is similar in many respects to neurons. Cardiac muscle tissue has autorhythmicity, the unique ability to initiate a cardiac action potential at a fixed rate – spreading the impulse rapidly from cell to cell to trigger the contraction of the entire heart. There are specific proteins expressed in cardiac muscle cells. These are mostly
Cardiac muscle along with polysaccharides (sugar chains) known as glycosaminoglycans. Together, these substances give support and strength to the muscle cells, create elasticity in cardiac muscle, and keep the muscle cells hydrated by binding water molecules. The matrix in immediate contact with the muscle cells is referred to as the basement membrane, mainly composed of type IV collagen and laminin. Cardiomyocytes are linked to the basement membrane via specialised glycoproteins called integrins. The physiology of cardiac muscle shares many similarities with that of skeletal muscle. The primary function of both muscle types is to contract, and in both cases a contraction begins