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Mark Scheme Transport Questions

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The IB mark scheme for some of the questions
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  1. Explain the relationship between the structure and function of arteries, veins and capillaries. (Total 8 marks)   (   [3 max]  for information on arteries) thick wall / elastic fibres to help withstand the high(er) pressure;outer fibrous coat prevents artery from rupturing under the high pressures;lumen small compared to wall thickness to maintain high pressure;except lumen large near the heart to conduct a large volume of blood;valves in aorta and pulmonary artery to prevent back flow into ventricles in diastole;layers of (smooth) muscle to allow arteries to contract / elastic recoil;allows the pressure to be altered (vasoconstriction and vasodilation);  (   [3 max]   for information on veins) lumen always large in relation to diameter;thin wall / more collagen and fewer elastic fibres (than arteries)since pressure low(er);very little muscle since not needed for constriction;valves to prevent back flow between pulses;  (   [3 max]   for information on capillaries) no muscle / elastic tissue since pressure very low;endothelial layer one cell thick to allow permeability / diffusion of chemicals / tissue fluid;small diameter leads to exchange;some fenestration / pores to allow rapid diffusion;no valves since pressure very low; [8] 2. Explain the events of the cardiac cycle. (Total 7 marks) ! node fires (electrical) signal throughout walls of atria to begin cycle;causing atria to undergo systole;! signal reaches atrioventricular node;which spreads signal throughout ( urkin#e fibres);causing ventricles to undergo systole;atrioventricular valves slap shut;causing $lub$ sound;after ventricles are emptied semilunar valves close;causing $dub$ sound;atrioventricular valves open;ventricles begin diastole and start filling;all four chambers are in diastole and filling;when atria filled and ventricles %&' filled cycle has ended;  Accept bicuspid and tricuspid valves as alternatives to atrioventricular valves. [7]   1  3. Marine mammals have a series of physiological responses to diving. This enables them to stay submerged for long periods in water colder than their body temperature. Collectively these responses are termed the diving reflex. o investigate the diving reflex in humans, heart rate changes in ten healthy sub#ects were monitored during facial immersions in water ranging from *+ to %*+. he data for this experiment is shown below.  ,- ,.& ,.- ,& ,- ,)& ,)- ercentage change in heart rate&-.&.-&-)&)-0&1ater temperature / 2+ 3ource4 5 6 7ork, Effect of 1ater emperature on 8iving 6eflex 9nduced :radycardia in umans,http4//kesler.biology.rhodes.edu/sci</7ork.html= (a)(i)tate the effect of facial immersion on heart rate over the range of temperatures shown on the graph....................................................................................................................................................................................................................................................... (1)  (ii)uggest one  reason for the relationship between facial immersion and heart rate....................................................................................................................................................................................................................................................... (1)  (b)>utline the effect of the water temperature on heart rate........................................................................................................................................................................................................................................................................... (1)  (c)+alculate the heart rate of a person immersed in water at a temperature of -*+, if their heart rate before immersion was %& beats per minute................................................................................................................................................................................................................................................................................................................................................................................................................  2   ..................................................................................................................................... (2)(Total 5 marks) (a)(i)immersing the face causes a lowering of the heart rate(ii)to reduce cardiac output;to preserve oxygen for brain / heart needs;slowing of metabolic rate;to reduce production of +>   / maintain blood p max (b)the lower the temperature, the greater the suppression of heart rate / effect more pronounced at lower temperatures  Numerical answers accepted.  (c)at - *+, expect a ?' (@ ') reduction in heart rate;therefore expect new heart rate of -A / -% beats per minute; [5]   4. 8iscuss the factors which affect the occurrence of coronary heart disease.  (Total 4 marks)  Named factors and explanation. genetic  some people predisposed for high cholesterol levels / high blood pressure;age  older people greater risk / less elasticity in arteries;sex  males at great risk than females;smoking  constricts blood vessels / increases blood pressure / heartBrate / decreases oxygenation of heart muscle;diet  increases fat / cholesterol / C8C in blood / leads to plaDue formation in arteries;exercise  lack of exercise increases risk;obesity  increase in blood pressure / leads to plaDue formation in arteries;  Accept any other factor correctly explained eg diabetes, atherosclerosis. Do not award a mark for the name of a factor and simply that it leads to !D . [4] 5. 8raw a labelled diagram to show the internal structure of the heart. (Total 6 marks)    Award  [1]   for each of the following structures clearly drawn and labelled correctly in a diagram of the heart. left and right ventricle;left and right atria;atrioventricular valves / bicuspid / mitral and tricuspid valves;semilunar valves;aorta and vena cava; pulmonary artery and pulmonary vein;ventricle wall thicker than atria;left ventricle wall thicker than right ventricle wall;  Do not award marks for a diagram with only the ventricles or   atria. !owever, it is not necessary to show the cordae tendinae. [6]  3
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