Redfrost
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I know the heart has it's own natural pacemaker with the av node which can control HR and stroke volume to a certain extent (am I right?). For a fast heartbeat it requires signal from the accelerators and inhibitory centres in the medulla but it confuses me a little I have some questions to help get my head round it:

1) is the av node part of the myogenic/self regulation of the heart or is the av node only activated (causing contraction of ventricles) when stimulated by the medulla?

2) for heart rate and stroke volume to increase can this be done by the heart itself or does it need stimulation from the medulla/autonomic nervous system?

I just just get confused as to when the autonomic nervous system comes into play, is it during any exercise ? Like when resting it wouldn't be needed would it?

Thanks : /
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Hype en Ecosse
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(Original post by Redfrost)
I know the heart has it's own natural pacemaker with the av node which can control HR and stroke volume to a certain extent (am I right?). For a fast heartbeat it requires signal from the accelerators and inhibitory centres in the medulla but it confuses me a little I have some questions to help get my head round it:

1) is the av node part of the myogenic/self regulation of the heart or is the av node only activated (causing contraction of ventricles) when stimulated by the medulla?

2) for heart rate and stroke volume to increase can this be done by the heart itself or does it need stimulation from the medulla/autonomic nervous system?

I just just get confused as to when the autonomic nervous system comes into play, is it during any exercise ? Like when resting it wouldn't be needed would it?

Thanks : /
Hey there!

Firstly it's the sinoatrial node which acts as the main pacemaker! The AV node is the bit that transfers the signal from the atria to the ventricles.

The nodes are self-regulatory and don't require stimulation from the medulla to fire. However, if the nodes fail, the heart muscle itself can initiate an action potential - this is part of the myogenic side of it all!

Increases in heart rate and stroke volume are mostly a result of the autonomic nervous system.

Keep in mind that the autonomic nervous system isn't only active during exercise! The balance between the sympathetic and parasympathetic systems play a key role in where the resting heart rate is! Think of it like the sinoatrial node has the capacity to work on its own, but IRL, the autonomic nervous system helps determine its firing frequency.

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Redfrost
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Report Thread starter 6 years ago
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(Original post by Hype en Ecosse)
Hey there!

Firstly it's the sinoatrial node which acts as the main pacemaker! The AV node is the bit that transfers the signal from the atria to the ventricles.

The nodes are self-regulatory and don't require stimulation from the medulla to fire. However, if the nodes fail, the heart muscle itself can initiate an action potential - this is part of the myogenic side of it all!

Increases in heart rate and stroke volume are mostly a result of the autonomic nervous system.

Keep in mind that the autonomic nervous system isn't only active during exercise! The balance between the sympathetic and parasympathetic systems play a key role in where the resting heart rate is! Think of it like the sinoatrial node has the capacity to work on its own, but IRL, the autonomic nervous system helps determine its firing frequency.

Posted from TSR Mobile
Thanks, that's helped : )
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