Cardiac physiology is one of the most fascinating basic science and medicine topics. The anatomy and physiology of the heart significantly influence the clinical presentation of various disease states. The heart is made up of three layers: the pericardium (the outermost layer), the endocardium (the innermost layer), and the myocardium (the middle layer), which will be the primary focus here. The myocardium consists of: The primary cardiac cells, cardiomyocytes, have a unique structure that shares features with both skeletal and smooth muscle, although they are not identical to either. Cardiac cells exhibit three interrelated physiological features: Each feature includes numerous physiological processes that work together to achieve a primary goal: cardiac contraction, which results in cardiac output. This chapter discusses various cardiac controllers that modulate heart function based on physiological demands. Finally, cardiac physiology also involves several physiological reflexes, which are examined in the concluding section of the chapter.