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B_ventrical and atrial_diastole

(2 marks)

The graph below shows pressure changes which take place in the left side of the heart during one complete cardiac cycle.

(b) Identify which of the diagrams above (page 8), A or B, corresponds to the ventricular pressure rise between 0.15 and 0.3 seconds on the graph. Explain your choice.

A. Because duringventrical systole, ventricle contracts and increases pressure inside it. Atrioventricular valves (tricuspid and bicuspid) are closed, preventing backflow of blood into atrium. Semilunar valves are opened, so when ventricles contract, formed high pressure inside them pushes blood towards aorta and pulmonary vein. (2 marks)

(c) The semi-lunar valves and the A-V valves respond differently during the ventricular pressure rise between 0.1 and 0.15 seconds.

(i) Identify the response of the A-V valves at 0.1 seconds.

_ they are opened during atrial systole enabling blood fill ventricle

(1 mark)

(ii) Identify the response of the semi-lunar valves at 0.15 seconds.

__semi lunar valves are opened during ventricular systole enabling blood go to the body through arteries____________________________________________________

(1 mark)

(iii) Explain how the structure of each valve type allows for these different responses.

A-V valves

They separate atriums and ventricles, and are connected to the ventricles via chorda tendons. These valves prevent flowing of blood again to the atriums, when ventricles contract, while tendons prevent valves from folding back into the atria. _____________________

(2 marks)

Semi-lunar valves

_they are located in the gap between arteries and ventricles, and has half-moon shape. They are opened only in one direction and prevent the backflow of blood to the ventricles when it contracts.__

(2 marks)

(d) Explain the increase in the atrial pressure at each of the following points:

· between 0 and 0.05 seconds

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