I am trying to understand the effect of aging on the sympathetic fibers of SA node. I know that aging shifts the vagal curve to left in frequency due to aging. However, I am interested if aging has similar effect on sympathetic fibers.

In young heart, heart's intrinsic functions can work with simultaneous parasympathetic and sympathetic processes. If there is no change in the sympathetic function, then those processes have to happen at different times. I am having this kind of schematic picture in my mind:

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where intrinsic functions occur in 100-110 BPM normally. However, aging shifts V1 to V2, no intersection anymore between V2 and S1.

What is the effect of aging on the sympathetic fibers of SA node?

  • $\begingroup$ Aging reduces mHR by reducing iHR and thus by reducing the pacemaker activity of the sinoatrial node of the heart. The progressive decrease in iHR with age necessitates a corresponding increase in sympathetic tone in order to maintain rHR $\endgroup$
    – user63862
    Mar 14, 2021 at 4:04


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