MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedonyuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 5. BLOOD AND LYMPH CIRCULATION PROCESSES AND THEIR PATHOLOGY

HEART FUNCTION

5. STROKE AND MINUTE VOLUMES OF THE HEART

The amount of Blood ejected by a Heart ventricle during each contraction is called the stroke volume (SV) or systolic volume. On average, it ranges from 60 to 70 ml. The volume of blood ejected by the right and left ventricles is equal.

Knowing The Heart rate (HR) and stroke volume, one can determine the cardiac output (CO), also known as the minute volume of Blood Circulation:

Class="center">CO = SV • HR.

At rest in a healthy adult, the average cardiac output is about 5 liters. During physical exertion, the stroke volume can double, and cardiac output can reach 20-30 liters.

Stroke volume and cardiac output characterize the Pumping Function of the Heart.

As the volume of blood entering the heart chambers increases, the force of contraction increases proportionally. This enhancement in contractile force depends on the stretching of the heart Muscle: the greater the stretch, the stronger the contraction. The physiologist Starling formulated the "law of the heart" (the Frank-Starling law): an increase in the heart's blood filling during diastole and the corresponding greater stretch of the myocardial fibers lead to an increase in the force of contraction.



Last update: 08/08/2026

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