Control of stroke volume

Many factors contribute to the regulation of stroke volume. Factors discussed in this section include  

Two important concepts to keep in mind throughout this discussion are that (1) the heart can only pump what it gets and (2) a healthy heart pumps all of the blood returned to it. The SA node may generate a heartbeat and cause the ventricles to contract however, these chambers must be properly filled with blood in order for this activity to be effective. On the other hand, the volume of blood that returns to the heart per minute may vary considerably. The heart has an intrinsic ability to alter its strength of contraction in order to accommodate these changes in volume. 

Diastole is the period in the cardiac cycle in which relaxation of the myocardium and ventricular filling take place. In an individual with a resting 

Diuretics are a group of therapeutic agents designed to reduce the volume of body fluids. Their mechanism of action is at the level of the kidney and involves an increase in the excretion of Na+ and Cl ions and, consequently, an increase in urine production. As discussed in Chapter 2, sodium is the predominant extracellular cation and, due to its osmotic effects, a primary determinant of extracellular fluid volume. Therefore, if more sodium is excreted in the urine, then more water is also lost, thus reducing the volume of extracellular fluids including the plasma. 

As plasma volume decreases, less blood is available for ventricular filling. 

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