Cardiac physiology
- DOI:
- 10.1093/med/9780199204854.003.160103_update_002
The function of the heart is to provide the tissues of the body with sufficient oxygenated blood and metabolites to meet the moment-to-moment needs as dictated by physical activity and postural and emotional changes.
Cardiac myocytes are the contractile cells of the heart and constitute the bulk of heart mass. There are differences between the myocytes of the ventricles, the atria, and the conduction system: ventricular myocytes are elongated cells, packed with myofibrils (the contractile apparatus) and mitochondria (for ATP production). Myofibrils are repeating units (sarcomeres) made up of thin actin filaments anchored at the Z-discs at either end of the sarcomere, and thick myosin filaments which interdigitate and interact with the thin filaments. Contraction results from sarcomere shortening produced by the ATP-dependent movement of the thin and thick filaments relative to one another. Transverse (T-) tubules facilitate extracellular Ca...
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