Cardiac physiology

Abstract

Cardiac physiology is one of the most interesting discussions both in basic science and clinic. Anatomy and physiology of the heart directly affect the clinical presentations of disease states. The heart is composed of pericardium (outmost layer), endocardium (innermost layer), and myocardium (middle layer), the last being more discussed here and consists of: • Cardiac connective tissue cells • Cardiomyocytes (which have contractile function) • Cardiac electrical and conduction system cells (consisting of "impulse-generating cells" and "specialized conductive cells") The main cardiac cells are cardiomyocytes with their unique structure having some shared features with both skeletal muscles and smooth muscles, though not completely similar with any of these two muscle types. Cardiac cells have three different but "highly interrelated" physiologic features: • Action potential • Excitation-contraction coupling (ECC) • Contractile mechanisms Each of the three is composed of numerous different physiologic chains to create together, and as a final outcome, a main goal: cardiac contraction leading to cardiac output. There are a number of cardiac controllers which modulate cardiac function based on physiologic demands, which are discussed in this chapter. And finally, a number of physiologic reflexes are involved in cardiac physiology discussed in the final part of the chapter.