History of Cardiovascular Physiology, Dr. D. Penney
Misconceptions about the Heart:
- Cardiac and skeletal muscle are both striated, and identical in their functional characteristics.
- Cardiac contractions occur only by virtue of central nervous system connections to the heart.
- Ventricular filling occurs as a purely passive process and is completely dependent upon atrial contraction.
- The major reason the mitral valve closes at the beginning of ventricular contraction is because of increasing pressure in the ventricle.
- The aortic valve closes at the end of the systole ejection because ventricular pressure falls below aortic pressure.
- The right and left heart pump exactly the same amount of blood per beat in every cardiac cycle.
- The right and left ventricles begin and end contractions at exactly the same time.
- Coronary blood flow is maximal when aortic pressure (ventricular pressure) is maximum. i.e. Blood flow is always maximal when arterial pressure is maximum.
- Blood flow in the up-raised arm declines sharply with resulting pain and/or numbness because the heart must pump blood up to the fingers against gravity.
- The heart increases its oxygen uptake by increasing both oxygen extraction from the blood and blood flow.
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