AndrewKn0x
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I've recently done the cardiac cycle in biology and though I found it very interesting, I've found it quite difficult. Usually I do really well in biology but this really threw me off. It's not the actual cardiac cycle itself, it's more do to with graphs, calculating bpm, pressure changes, valves in the veins etc rather than the actual cycle because that's simple, if that even made sense at all? Anyway, it would be great if somebody could explain all of the graphs and calculations and pressure changes i.e. the more challenging sub-topics of the topic that would be great. Thanks!
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JulieWaters
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(Original post by AndrewKn0x)
I've recently done the cardiac cycle in biology and though I found it very interesting, I've found it quite difficult. Usually I do really well in biology but this really threw me off. It's not the actual cardiac cycle itself, it's more do to with graphs, calculating bpm, pressure changes, valves in the veins etc rather than the actual cycle because that's simple, if that even made sense at all? Anyway, it would be great if somebody could explain all of the graphs and calculations and pressure changes i.e. the more challenging sub-topics of the topic that would be great. Thanks!
I've recently just done this topic so I think I'll be able to explain to you the pressure changes.

So the first stage is called is atrial sytole, where the atria contract, decreasing the volume and increasing the pressure of this chamber. Easy way to remember this is to clench your hand, this simulates a contraction, the volume inside your hand decreases and so the pressure must increase. ( Generally when the volume decreases the pressure increses).
The atrialventricular valves open due to the pressure being higher in the atria then the ventricles.
The blood goes from high to low pressure down a pressure gradient. The blood therefore goes into the ventricles.
As the blood flows into the ventricles the pressure increases slightly.

Then you have ventricular systole where your atria relax(and so their pressure gets reduced , to what they were before) and your ventricles contract, decreasing the volume and increasing the pressure.
Now the pressure is higher in the ventricles then the atria so the atrioventricular valves close.
The semi - lunar valves open due to the pressure being higher in the ventricles then in the arteries.
The blood similarly flows down a pressure gradient into the arteries.

You then have atrial and ventricular disystole which involves the atria and ventricles to relax. The pressure is now higher in the arteries then the ventricles and so the semi-lunar valves close. The blood goes to the rest of your body and when it comes back to the heart, the blood flows into the atria due to the higher pressure in the veins. As the ventricles continue to relax their pressure falls below the pressure of the atria causing the AV (atrioventricular ) valves to open and blood passively (with no energy) enters the ventricles. The atria contracts and the whole cycle starts again.

Hope this helps!!
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AndrewKn0x
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(Original post by JulieWaters)
I've recently just done this topic so I think I'll be able to explain to you the pressure changes.

So the first stage is called is atrial sytole, where the atria contract, decreasing the volume and increasing the pressure of this chamber. Easy way to remember this is to clench your hand, this simulates a contraction, the volume inside your hand decreases and so the pressure must increase. ( Generally when the volume decreases the pressure increses).
The atrialventricular valves open due to the pressure being higher in the atria then the ventricles.
The blood goes from high to low pressure down a pressure gradient. The blood therefore goes into the ventricles.
As the blood flows into the ventricles the pressure increases slightly.

Then you have ventricular systole where your atria relax(and so their pressure gets reduced , to what they were before) and your ventricles contract, decreasing the volume and increasing the pressure.
Now the pressure is higher in the ventricles then the atria so the atrioventricular valves close.
The semi - lunar valves open due to the pressure being higher in the ventricles then in the arteries.
The blood similarly flows down a pressure gradient into the arteries.

You then have atrial and ventricular disystole which involves the atria and ventricles to relax. The pressure is now higher in the arteries then the ventricles and so the semi-lunar valves close. The blood goes to the rest of your body and when it comes back to the heart, the blood flows into the atria due to the higher pressure in the veins. As the ventricles continue to relax their pressure falls below the pressure of the atria causing the AV (atrioventricular ) valves to open and blood passively (with no energy) enters the ventricles. The atria contracts and the whole cycle starts again.

Hope this helps!!
Wow. Clear and easy to understand! Thank you SO much! I understand it so much more now.
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JulieWaters
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(Original post by AndrewKn0x)
I've recently done the cardiac cycle in biology and though I found it very interesting, I've found it quite difficult. Usually I do really well in biology but this really threw me off. It's not the actual cardiac cycle itself, it's more do to with graphs, calculating bpm, pressure changes, valves in the veins etc rather than the actual cycle because that's simple, if that even made sense at all? Anyway, it would be great if somebody could explain all of the graphs and calculations and pressure changes i.e. the more challenging sub-topics of the topic that would be great. Thanks!
Name:  2029_Cardiac_Cycle_vs_Heart_Sounds.jpg
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For the graph interpretation our teacher taught us a trick to remembering where the valves open and close. On the graph it already has labelled where the valves open and close, but you can use COCO to work this out

ImageThis graph is easier to explain COCO. Basically you need to remember that the bottom two labels (A and D) on the graph are the AV valves and the top two (B and C ) are the semi-lunar valve. ( To help you remember this just visualize the heart and the semi lunar valves seem higher up then the AV valves). So you simply write COCO as you go across the graph curve, A (C), B (O), C (C), D (O). C stands for closed and O stands for open. So now you can tell where the different valves open and close at different points.

To understand this you can refer back to my other reply with pressures and see what pressures you need to compare to work out whether the valve is open or closed.
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JulieWaters
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(Original post by AndrewKn0x)
Wow. Clear and easy to understand! Thank you SO much! I understand it so much more now.
You're welcome! I'm glad this was helpful!
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AndrewKn0x
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(Original post by JulieWaters)
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For the graph interpretation our teacher taught us a trick to remembering where the valves open and close. On the graph it already has labelled where the valves open and close, but you can use COCO to work this out

ImageThis graph is easier to explain COCO. Basically you need to remember that the bottom two labels (A and D) on the graph are the AV valves and the top two (B and C ) are the semi-lunar valve. ( To help you remember this just visualize the heart and the semi lunar valves seem higher up then the AV valves). So you simply write COCO as you go across the graph curve, A (C), B (O), C (C), D (O). C stands for closed and O stands for open. So now you can tell where the different valves open and close at different points.

To understand this you can refer back to my other reply with pressures and see what pressures you need to compare to work out whether the valve is open or closed.
That's such a clever way to remember it! Great, thank you.
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Sarahk12
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(Original post by AndrewKn0x)
That's such a clever way to remember it! Great, thank you.
This is awesome! I'm literally just doing this topic and you've explained it so well!
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nisha.sri
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(Original post by JulieWaters)
I've recently just done this topic so I think I'll be able to explain to you the pressure changes.

So the first stage is called is atrial sytole, where the atria contract, decreasing the volume and increasing the pressure of this chamber. Easy way to remember this is to clench your hand, this simulates a contraction, the volume inside your hand decreases and so the pressure must increase. ( Generally when the volume decreases the pressure increses).
The atrialventricular valves open due to the pressure being higher in the atria then the ventricles.
The blood goes from high to low pressure down a pressure gradient. The blood therefore goes into the ventricles.
As the blood flows into the ventricles the pressure increases slightly.

Then you have ventricular systole where your atria relax(and so their pressure gets reduced , to what they were before) and your ventricles contract, decreasing the volume and increasing the pressure.
Now the pressure is higher in the ventricles then the atria so the atrioventricular valves close.
The semi - lunar valves open due to the pressure being higher in the ventricles then in the arteries.
The blood similarly flows down a pressure gradient into the arteries.

You then have atrial and ventricular disystole which involves the atria and ventricles to relax. The pressure is now higher in the arteries then the ventricles and so the semi-lunar valves close. The blood goes to the rest of your body and when it comes back to the heart, the blood flows into the atria due to the higher pressure in the veins. As the ventricles continue to relax their pressure falls below the pressure of the atria causing the AV (atrioventricular ) valves to open and blood passively (with no energy) enters the ventricles. The atria contracts and the whole cycle starts again.

Hope this helps!!
Omg thank you so much for this ! This is so clear and easy to understand.
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