The Cardiac Cycle

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  • Created by: shyde7
  • Created on: 13-04-16 15:48
What is ventricular systole?
When both left and right ventricles pump together.
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Where do contractions start in ventricular systole?
At the apex (base), so the blood is pushed upwards towards the arteries.
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What is diastole?
When the muscular walls of all four chambers relax.
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What causes the chambers to increase in volume during diastole?
Elastic fibres.
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Why do the chambers increase in volume during diastole?
To allow blood to flow in from the veins.
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What is atrial systole?
When both the right and left atria contract together.
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How much pressure is created by the contraction in atrial systole and why?
Only a small increase in pressure because the walls are thin.
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What do valves do?
They ensure than blood flows int he right direction.
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How are valves opened and closed?
By changes in blood pressure in the heart chambers.
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What happens to the pressure in the ventricles after ventricular systole?
The pressure drops rapidly below the pressure in the atria.
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What pushes the atrio-ventricular valves open?
Blood in the atria.
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What happens to the pressure in the atria and ventricles as they fill with blood?
The pressure rises slowly.
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What are the valves doing while the atria contract?
They remain open.
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When do the atrio-ventricular valves close?
When the atria begin to relax.
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Why do the atrio-ventricular valves close?
Because of the swirling action in the blood around the valves when the ventricle is full.
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What happens to the pressure of the ventricles as the ventricles begin to contract
The pressure increases.
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What happens when the pressure in the ventricles is more than the pressure in the atria?
The blood starts to move upwards.
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What causes the valves to keep closed?
The blood moving upwards as the movement fills the valve pockets.
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What stops the valves from turning inside out and blood flowing back into the atria?
The tendinous chords attached to the valves.
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When is the pressure in the major arteries higher than the pressure in the ventricles?
Before ventricular contraction.
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Beofre ventricular contraction, what is happening to the semilunar valves?
They are closed.
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Ventricular systole raises the blood pressure where?
In the venricles, very quickly.
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When are the semilunar valves pushed open?
When the pressure in the venticles rises above the pressure in the major arteries.
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Why is it important that the blood is under very high pressure?
So it is pushed out from the ventricles in a powerful spurt
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What happens to elastic tissue in the walls of the ventricles during diastole?
The elastic tissue recoils.
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Why does the elastic tissue recoil?
To stretch the muscle out again and reutrn the ventricle to its original size.
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What effect does the recoil of the elastic tissue have on the presssure in the ventricles?
It drops quickly.
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Wat happens when the pressure in the venticles drops below the pressure in the major arteries?
The blood starts to flow back towards the ventricles.
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How are the semilunar valves pushed closed?
By the blood collecting in the pockets of the valves.
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Wy is the blood collecting in the pockets of the semilunar valves a good thing?
Because it prevents blood returning to the ventricles.
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The 'pulse' we can easily feel on our neck is actually what?
The pressure wave reated when the left semilunar valve closes.
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How do the tissues require blood to be delivered?
In an even flow rather than the rapid spurt.
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What do the artery walls close to the heart have a lot of?
Elastic tissue.
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What happens to the walls when blood leaves the heart?
The walls stretch.
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When does the pressur of the aorta start to drop?
When the blood moves out of the aorta.
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What helps maintain the blood pressure in the arota?
The elastic recoil of the walls.
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What happens to the fluctuations and pressure the further along the arteries the blood flows?
The further along the blood moves the more the blood pressure drops.
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What keeps the blood flowing towards the tissues?
The maintence of the pressure gradienct between the aorta and the arterioles.
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Other cards in this set

Card 2

Front

Where do contractions start in ventricular systole?

Back

At the apex (base), so the blood is pushed upwards towards the arteries.

Card 3

Front

What is diastole?

Back

Preview of the front of card 3

Card 4

Front

What causes the chambers to increase in volume during diastole?

Back

Preview of the front of card 4

Card 5

Front

Why do the chambers increase in volume during diastole?

Back

Preview of the front of card 5
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