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3. What is the advantage of having two separate pumps rather than one?
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3. The RHS generates pressure to send blood to lungs where pressure drops. The LHS generates more pressure so blood can travel to rest of the body fast enough to generate high MR.
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4. Why does the cardiac muscle need a rich supply of blood?
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4. It needs a rich supply of oxygen and glucose for high rates of aerobic respiration to produce a lot of ATP for heart muscle contraction.
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5. Why is the muscle of the left ventricle thicker than the right?
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5. The left ventricle needs to contract with more force so there is a higher pressure, so blood can be pumped all around the body.
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6. Describe what happens during diastole. 7. During diastole are the semi-lunar valves open or closed? Why?
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6. The heart is relaxed and atria are a filling with blood from the vena cava and pulmonary veins.7. The semi lunar valves are closed because the pressure in the arteries is higher than in the ventricles (prevents backflow).
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8. What happens during atrial systole?
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8. -Blood fills the atria (from vena cava and pulmonary veins) which increases the pressure.-The atria then contracts which increases the pressure above the ventricular pressure.-The atrioventricular valves open and blood flows into the ventricles.
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9. What happens during ventricular systole?
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9. -Blood flows into the ventricles .-The pressure in the ventricles increases.-The ventricles contract which increases the pressure above the arterial pressure.-The AV valves close and the semilunar valves open and blood flows into aorta and pulmonary artery.
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10. Why do the AV valves close during ventricular systole?
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10. because the pressure in ventricles is higher than the pressure in the atrium.
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11. Summarise the sequence of events which control the cardiac cycles.
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11. -Electrical impulses sent out from SAN.-Impulses spread across walls of both atria.-Atria contract.-Impulses reach AVN where they are delayed (ensures atria are empty)-AVN sends out impulse.-Impulse pass down bundle of His.-Activity is releases at base of ventricles where they are conducted upwards by Purkinje fibres.-Ventricles contract.
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12. What is the stroke volume?13. What is the cardiac output?
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12. The volume of blood pumped out from one ventricle during each contraction.13. The total volume pumped out from one ventricle per minute.
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14. How do you work out cardiac output?15. Why does person who does more aerobic work have a larger stroke volume?
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14. stroke volume x heart rate15. Because their ventricles are larger so they are able to fill with a larger volume of blood. Also more muscle means a stronger contraction so more blood is pushed out per beat.
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16. What is mass flow?17. Describe the structure of the artery wall?
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16. The bulk movement of substances from one area to another due to differences in pressure.17. They are very thick. They have an inner coat of a single layer of endothelium. They have a lot of elastic tissue and some muscle tissue.
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18. Why is it an advantage that the endothelium is very smooth?19. How do the arteries maintain pressure?
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18. It reduces friction between blood and vessel wall.19. The elasticity in the walls allows them to stretch as the high pressure blood is pumped out. This makes the artery wider and reduces the pressure a little. The elastic then recoils . This reduces fluctuations in pressure.
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20. Why do arteries near the heart have more elastic fibres?
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20. There is a greater blood pressure closer to the heart and large fluctuations. Stretch and recoil of elastic tissue in large arteries reduce fluctuation flow before blood reaches arterioles (less need for elastic tissue).
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21. Describe structure of arterioles?
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21. They have a lot of muscle tissue. They are much thinner than arteries. They have an inner coat of a single layer of endothelium.
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