Final answer:
The two factors that can be altered to change cardiac output are heart rate and stroke volume. Influences on these factors include autonomic innervation, endocrine control, preload, contractility, afterload, and inotropic agents such as electrolytes.
Step-by-step explanation:
The two factors that can be changed to alter cardiac output (Q) are heart rate (HR) and stroke volume (SV). Cardiac output is the measurement of blood flow from the heart through the ventricles, typically measured in liters per minute. An increase in either heart rate or stroke volume, or both, will result in an increase in cardiac output, which in turn elevates blood pressure and promotes blood flow. The primary factors influencing heart rate include autonomic innervation and endocrine control, as well as environmental factors such as electrolytes, temperature, and metabolic products. Stroke volume is controlled primarily by preload, which is the stretch on the ventricles prior to contraction; contractility, or the force of the contraction; and afterload, the force the ventricles must overcome to pump blood against the resistance in the vessels. Additionally, electrolytes can be considered as either positive or negative inotropic agents affecting stroke volume.