This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
True about stroke volume is? 
Select and explain. 
A. Decreases by increase in hea rate, B. Determined by pre-diastolic volume, C. Determined by afterload, D. Is equal to cardiac output
A: Decreases by increase in hea rate
Answer: A: Decreases by increase in hea rate 
Explanation: Decreases by increase in hea rate REF: Ganong's 22' e p. 570-571 Stroke volume = cardiac output/hea rate (amount of blood pumped by hea per beat), hence stroke volume is indirectly propoional to hea rate, hence increases. Hea rate decreases stroke volume. After load is determined by peripheral resistance, hence nothing to do with stroke volume determination. Stroke volume depends upon end diastolic volume.