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Author Topic: How is heart rate controlled?  (Read 6233 times)

thedoc

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How is heart rate controlled?
« on: 21/03/2012 09:04:01 »
Steven Wasmer  asked the Naked Scientists:
   
Dear naked scientists,

I was wondering what physical processes take place in order to command a change in heart rate?

As we all know resting heart rate is an indicator of cardiovascular health. What parameters must be met for the heart to slow? Does it slow due to increased lung efficiency, higher red blood cell count, larger volumes of blood moved per beat or more efficient use of the blood?

Conversely what causes my heart to increase its BPM?

Does the brain say "I'm moving the muscles so I better increase the BPM or is there another process at work which measures O2 saturation and then makes the request for more blood flow?

Thank you for all the great shows,

Steve    

What do you think?
« Last Edit: 21/03/2012 09:04:01 by _system »

cheryl j

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Re: How is heart rate controlled?
« Reply #1 on: 17/04/2012 03:57:12 »
Heart rate is controlled by multiple factors. Unlike skeletal muscle cells, heart cells can and do contract without a nerve telling it to. The group of heart muscle cells called the sinoatrial node or pacemaker establish the rhythm for the rest of the heart, because they beat the fastest.

But nerves connected to the heart, as well as hormones (epinephrine, norepinephrine), can act as accelerators to speed up or slow down the heart when necessary. Heart rate increases when sensory nerves signal the brain that the body is oxygen deprived or blood pressure is too low. Low oxygen, high CO2, or increases in acid, are detected by chemoreceptors located in the aorta, carotid arteries and the brain itself. Low blood pressure is detected by baroreceptors in the aorta and carotid arteries that respond to stretch, or rather lack of it.

Lmnre

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Re: How is heart rate controlled?
« Reply #2 on: 19/04/2012 13:07:12 »
the sinoatrial node or pacemaker establish the rhythm for the rest of the heart, because they beat the fastest.
Does this mean that, in the natural cyclical contractions of the different parts of the heart, that the SA node has the shortest cycle and, thus, activates first and triggers the other contractions?

cheryl j

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Re: How is heart rate controlled?
« Reply #3 on: 21/04/2012 03:24:46 »
Yes, I believe that's right. The muscles cells in the ventricles contract spontaneously at a slower rate than the cells in the SA node in the atria. When there is damage to the fibres that transmit the impulse down to the ventricles (called heart block) the ventricles will start contracting at a much slower rate, like 40 beats a minutes instead of 60-70.

 

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