Final answer:
When afterload increases, it becomes more difficult for ventricles to pump blood through the blood vessels, as there is more resistance to overcome. This is often associated with conditions like hypertension. However, increased pressure in veins can lead to increased venous flow back to the heart. The correct option is 1) The volume of venous blood that returns to the right atrium increases.
Step-by-step explanation:
When afterload increases, it becomes harder for the ventricle to push blood through the blood vessels. Afterload is the pressure against which the heart must work to eject blood during systole.
It is essentially the back pressure exerted by arterial blood. Increased afterload means higher tension and pressure the ventricles must generate to pump blood against the resistance in the vessels, which can result from conditions like hypertension or stenosis of the valves.
Venous return and preload are affected by different factors such as the volume of the blood, the compliance of the veins, and the activity of skeletal muscle and respiratory pumps.
In contrast to afterload, when the workload on the ventricles is decreased, as with vasodilation or the reduction of blood viscosity, resistance decreases and afterload is reduced.
Importantly, when it comes to venous flow, increased pressure actually leads to increased flow because the pressure in the veins is generally low and must be lower than the atrial pressure during diastole to facilitate blood flow back to the heart. The correct option is 1) The volume of venous blood that returns to the right atrium increases.