The Heart Flashcards
Where do the right and left hand sides of the heart pump blood too?
The right side pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood to the whole body
Explain how the ventricles of the heart are adapted for their function
The ventricles have thicker walls than the atria, because they have to push blood out of the heart where as the atria just need to push blood a small distance into the ventricles
How is the left ventricle in the heart adapted for their function?
The left ventricle has thicker, more muscular walls than the right ventricle, because it needs to contract powerfully to pump blood all the way around the body. The right side only needs to get blood to the lungs
How are the valves in the heart adapted to their function?
The atrioventricular (AV) valves link the atria to the ventricles and stop blood flowing back into the atria when ventricles contract. The semi-lunar (SL) valves link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after the ventricles contract
How are the cords in the heart adapted for their function?
The cords attach the atrioventricular valves to the ventricles to stop them being forced up into the atria when the ventricles contract
How many ways do the valves in the heart open?
They only open one way
What do the opening and closing of valves depend on?
Whether the valves are opened or closed depends on the relative pressure of the heart chambers. If there’s a higher pressure behind the valve, it’s forced open. If there’s a higher pressure in front of the valve, it’s forced shut. This means blood only flows in one direction through the heart
What is the cardiac cycle?
The cardiac cycle is an ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating round the body
What changes when the atria and ventricles contract?
The volume of the atria and the ventricles changes as they contract and relax. Pressure also changes due to the changes in volume - decreasing the volume of a chamber by contraction will increase the pressure
What are the three stages the cardiac cycle can be simplified in too?
- Ventricles relax, atria contract
- Ventricles contract, atria relax
- Ventricles relax, atria relax
Explain the first stage in the cardiac cycle
The ventricles are relaxed. The atria contract, decreasing the volume of the chambers and increasing the pressure of the chambers. This pushes the blood into the ventricles. There’s a slight increase in ventricular pressure and chamber volume as the ventricles receive the ejected blood from the atria
Explain the second stage in the cardiac cycle
The atria relax. The ventricles contract, decreasing their volume and increasing their pressure. The pressure becomes higher in the ventricles than in the atria, which forces the AV valves shut to prevent back flow. The pressure in the ventricles is also higher than in the aorta and pulmonary artery, which forces open the SL valves and blood is forced out into these arteries
Explain the third stage in the cardiac cycle
The ventricles and atria both relax. The higher pressure in the aorta and pulmonary artery closes the SL valves to prevent back flow into the ventricles. Blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and the pulmonary vein. In turn this starts to increase the pressure in the atria. As the ventricles continue to relax, their pressure falls below the pressure of the atria and so the AV valves open. This allows blood to flow passively into the ventricles from the atria. The atria contract and the process starts again
