CAIE A Level Biology 9700 · Transport in mammals
Describe the internal structure of the mammalian heart, explaining the difference in thickness between the walls of the atria and ventricles and between the left and right ventricles. Also describe the pressure changes and valve movements that occur during the cardiac cycle, and explain the roles of the sinoatrial node, atrioventricular node and Purkyne tissue in coordinating the heartbeat.
7 marks, so the mark scheme is looking for about 7 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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