To answer this question effectively, we need to understand the relationship between stroke volume and various physiological factors:
- a) Increased ADH: Antidiuretic hormone (ADH) primarily affects water retention in the kidneys, which could lead to increased blood volume rather than a decrease in stroke volume.
- b) Increased sympathetic stimulation: Increased sympathetic stimulation generally enhances heart rate and contractility, leading to an increased stroke volume. Therefore, this would not decrease stroke volume.
- c) Increased afterload: Afterload refers to the resistance the heart must work against to eject blood. An increase in afterload can impede the heart’s ability to eject blood effectively, thereby decreasing stroke volume.
- d) Increased preload: Preload is the initial stretching of the cardiac myocytes prior to contraction, which usually increases stroke volume via the Frank-Starling mechanism. Thus, increased preload is unlikely to decrease stroke volume.
- e) Increased blood volume: Higher blood volume generally leads to increased preload and therefore would not decrease stroke volume.
Based on this analysis, the correct answer to the question is c) increased afterload. Increasing afterload requires the heart to exert more force to overcome the resistance, which can lead to a decrease in the amount of blood ejected with each heartbeat, thus reducing stroke volume.