A question about the cardiovascular system

[Callum]

When an organ such as the kidney is donated, the total resistance withing the vessels increases (because a kidney which represents a resistance was connected in parallel).

Because of this increase in resistance, flow of blood decreases obviously. But my question is, why does the cardiac output decrease and the heart rate decrease (a bradycardia in patients with 1 kidney is normal). Isn't the heart supposed to compensate for this decrease in flow by increasing its cardiac output?!! I found this confusing.

 

Please Help

Thank you