ANS effect on SA node Conduction Velocity

[MedStudent219]

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Hi all, I've been looking for information everywhere and trying to reason my way through understanding this. But how come the conduction velocity of the AV node is only really affected by changes in the ANS? Are there no changes in conduction velocity in other parts of the system? namely the SA node?

Any explanation is appreciated 🙂 thanks!

 

[FalconSlice]

There are changes in the SA node via both parasympathetic and sympathetic innervation:

CV Physiology | Regulation of Pacemaker Activity

www.cvphysiology.com

 

[MedStudent219]

There are changes in the SA node via both parasympathetic and sympathetic innervation:

CV Physiology | Regulation of Pacemaker Activity

www.cvphysiology.com

Yeah I understand that there's changes in relation to SA node (HR) but I was more so curious about conduction velocity specifically and why variation in the ANS mainly affects the AV node.

 

[aldol16]

I'm sure it has to do with receptor density and biochemical mechanisms like that, but the logic should be clear. The SA node must be affected by ANS because that's how you increase or decrease heart rate. That's also why you get inappropriate bradycardia in neurogenic shock.

The AV node is affected because it's the prime point where you can delay the signal. After the AV node, the signal will divide anatomically as it traverses the septum. So the AV node is the bottleneck that makes most sense to delay the signal.