Topic 3---B: More Exchage and Transport Systems- 4. The Heart Flashcards
What does the right side of the heart do?
pump deoxygenated blood to the lungs
What does the left side of the heart do?
pump oxygenated blood to the whole body
Why is the left ventricle thicker than that of the right?
- thicker muscle to contract with greater force
- to generate higher pressure to pump blood around entire body
How is the left ventricle adapted to do its job efficiently?
- the left ventricle of the heart is thicker, more muscular walls than the right ventricle
- this allows it to contract more powerfully and pump blood all around the body
What is the structure of the right side of the heart?
- its less muscular so its contractions are only powerful enough to pump blood to the nearby lungs.
How are the ventricles adapted to do its job efficiently?
- they have thicker walls than the atria so they can push blood out of the heart
- whereas the atria just need to push blood a short distance into the ventricles
How are the atrio-ventricular valves adapted to do its job efficiently?
- they link the atria to the ventricles and stop blood flowing back into the atria when the ventricles contract
How are the semi-lunar valves adapted to do its job efficiently?
- they link the ventricles to the pulmonary artery and aorta and stop blood flowing back into the heart when the ventricles contract.
How are cords adapted to do its job efficiently?
- they attach the atrio-ventricular valves to the ventricles to stop them being forced up into the atria when the ventricles contract
What determines whether heart valves are open or closed?
the relative pressure of the heart chambers
What happens if there is a higher pressure behind the valve?
its forced open
What happens if there is a higher pressure in front of the valve?
its forced shut
What do heart valves mean to the flow of blood?
flow of blood is unidirectional so it only flows in one direction
What is the cardiac cycle?
its an ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating around the body.
What are the 3 stages of the cardiac cycle?
- atrial systole
- ventricular systole
- diastole
What occurs in atrial systole?
- ventricles are relaxed
- the atria contract
- volume of the Chambers decreases and pressure increases
- atrio- ventricular valves open when pressure in atria exceeds pressure in ventricles
- this pushes blood into the ventricles which increases ventricular volume and pressure as they are relaxing.
Ventricular systole
- atria relax
- ventricles contract decreasing their volume in the chamber and increasing their pressure.
- pressure becomes higher in the ventricles compared to the atria so the atrio- ventricular valves shut
- pressure in ventricles is also higher than the aorta and pulmonary artery forcing the semi- lunar valves open
- so blood is pushed out of ventricles and into arteries
Diastole
- atria and ventricles relax so volume and pressure is increased
- the semi-lunar valves shut when pressure in the pulmonary artery and aorta exceeds the pressure in the ventricles
- blood returns to the heart and atria fill with blood again due to the higher pressure in the vena cava and pulmonary vein
- atria pressure increases causing the av valves to open allowing blood to flow passively into the ventricles without contraction
What is cardiac output?
Volume of blood pumped by the heart per minute
Cardiac output formula
Stroke volume x heart rate
What is heart rate?
the number of beats per minute
What is stroke volume?
the volume of blood pumped during each heartbeat
