Turn over 13 4 The autonomic nervous system controls the heart rate. (a) The diagram shows a human brain. W X Y Z (i) Which region of the brain controls the heart rate? (1) A W B X C Y D Z (ii) Which one of the following would lead to an increase in heart rate? (1) A release of acetylcholine by the sympathetic nervous system B release of acetylcholine by the parasympathetic nervous system C release of noradrenaline by the sympathetic nervous system D release of noradrenaline by the parasympathetic nervous system 14 (b) The graphs show the pressure changes that occur in a healthy heart and the pressure changes that occur in a heart with an atrioventricular valve that leaks. 16 14 12 10 8 6 4 2 0 0.0 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Pressure / kPa Time / s Healthy heart 16 14 12 10 8 6 4 2 0 0.0 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Pressure / kPa Time / s Heart with an atrioventricular valve that leaks Key left ventricle aorta left atrium (i) An atrioventricular valve in the healthy heart has a surface area of 3.5 cm2. Determine the force that is applied to this atrioventricular valve when it closes. Use the formula Pressure in kPa = Force in newtons Area in m2 (3) Answer .............................................................. newtons Turn over 15 (ii) Explain why people with an atrioventricular valve that leaks find exercise difficult. 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(Total for Question 4 = 9 marks) 16 BLANK PAGE