Cardiac muscle
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Cardiac muscle is a type of striated muscle found within the heart. Its function is to "pump" blood through the circulatory system by contracting.
Unlike skeletal muscle, which contracts in response to nerve stimulation, and like smooth muscle, cardiac muscle is myogenic, meaning that it stimulates its own contraction without a requisite electrical impulse. A single cardiac muscle cell, if left without input, will contract rhythmically at a steady rate; if two cardiac muscle cells are in contact, whichever one contracts first will stimulate the other to contract, and so on. This transmission of impulses makes cardiac muscle tissue similar to nerve tissue, although the cells are connected by intercalated discs, which conduct electrical potentials directly, rather than the chemical synapses used by neurons.
Specialized pacemaker cells normally determine the overall rate of contractions. The nervous system does contact the heart, but only sends signals to speed up or slow down the heart rate, rather than controlling each beat. Since cardiac muscle is myogenic, the pacemaker serves only to modulate the cells; the cardiac muscles would still fire in the absence of a pacemaker, albeit randomly, and the heart would go into fibrillation.
See also
| Muscular system |
| Muscular tissue - Cardiac muscle - Skeletal muscle - Smooth muscle - Muscle contraction - List of muscles of the human body |