As the 400 metre hurdler’s blood flows around his body, its pressure and velocity changes, as shown: a) Which of the blood vessels, A, B or C, represents veins? (1 mark) b) State three characteristics or functions of arteries. (3 marks) c) Where is myoglobin found in the body and what is its role during exercise? (2 marks) PressureVelocity Blood vessels AHigh Blood vessels BLow Blood vessels CLowMedium

a) * C. b) * (Thick) Elastic walls * (Small) lumen * (Smooth) muscle layer * Carrying blood away from the heart/ to tissues/muscles * Cushion and smooth out/recoil/pulse/ withstand pumping action/pressure/ velocity from heart c) * In muscle * Stores/supplies/carries oxygen

a) During a game, the blood pressure of a player increases. What factors determine the ‘blood pressure’ in arteries? (3 marks) b) During a game, a player’s arterio-venous oxygen difference (a-vO2 diff) will increase. What is the significance of this increase in a-vO2 diff to the player? (3 marks) a) * Contraction of the heart/stroke volume/ejection fraction/heart rate; * Increased blood flow/cardiac output/Q; * (Peripheral) resistance/friction/ elasticity of walls; * Blood viscosity/sweating/loss of fluid; * Blood vessel length/distance from the heart; * Blood vessel diameter/size/ vasoconstriction/vasodilation/cross sectional area/lumen size; * Health factor/atherosclerosis/diet/ stress/drugs/hereditary; * Age/level of fitness/intensity of exercise; b) * Difference between oxygen content of arterial and venous blood * More oxygen is needed/extracted by the muscles; * Used/needed for energy/ATP production; * Endurance/stamina/aerobic exercise; * Leads to improved performance; * Increased oxygen diffusion at lungs/alveoli/muscle; * More oxygen in blood; * More CO2 in blood/produced;

a) Running helps the 'venous return' mechanism. Explain how the venous return mechanism works. (3 marks) b) For effective performance, games players require oxygen to be delivered to the muscles and carbon dioxide to be removed. State two ways in which carbon dioxide is transported by the blood. (2 marks) a) * Muscle/skeletal pump/respiratory pump; * One-way/pocket valves in veins/give direction; * Contraction of leg muscles compresses veins; * Breathing mechanism/inspiration increases pressure compresses veins; * Suction pressure of heart/heart draws up blood. b) * As bicarbonate/hydrogen carbonate ions/ carbonic acid; * Dissolved in plasma; * Combined/attached with plasma proteins/haemoglobin / forms carbaminohaemoglobin

a) When a performer is running, blood is redirected to the working muscles. Explain how this redistribution of blood is achieved. (3 marks) b) Figure 1 shows the oxyhaemoglobin dissociation curve. i) Use Figure 1 to explain how oxygen is released by the blood and supplied to muscles. (2 marks) ii) During exercise the curve shifts to the right. Explain the causes of this shift and the effect this has on oxygen delivery to the muscles. (4 marks)

a) * Increased metabolic activity/increased carbon dioxide/increased lactic acid/drop in pH in the blood/increased acidity * Detected by chemoreceptors * Message to medulla/vasomotor control centre * Autonomic/sympathetic system/adrenaline/noradrenaline produced * Pre-capillary sphincters/arterioles * Vasoconstriction – to organs * Vasodilation – to muscles b) i) * Oxygen carried in haemoglobin / haemoglobin able to carry 4 oxygen molecules. * Amount of O2 combining with haemoglobin depends on partial pressure of O2 (PO2). * Where O2 concentration is high (e.g. at lungs) then haemoglobin becomes fully saturated (oxyhaemoglobin). * Where O2 concentration is low (e.g. working muscle cells) haemoglobin releases its oxygen to the surrounding cells. * During exercise even more O2 is released as PO2 in muscle cells falls even lower. ii) * Increase in (blood/body) temperature * Increase in blood carbon dioxide concentration (pCO2) * Increase in blood acidity/increase in hydrogen ions/decrease in pH * Bohr shift * Resulting in less saturation/reduced affinity of haemoglobin with oxygen * An increase in oxygen release/ oxyhaemoglobin dissociation to muscles/muscles receive more O2

a) State three ways in which carbon dioxide is transported in the blood. (3 marks) b) Explain how oxygen is taken up by haemoglobin from the lungs and released at the muscle site. (3 marks) c) Explain the variation in blood pressure and blood velocity shown in the graph below. (5 marks)

a) * In blood plasma. * Combined with haemoglobin. * Forms bicarbonate. b) * Forms oxyhaemoglobin/Hb O2 * At lungs - high partial pressure of O2/ blood – low partial pressure of O2; * Haemoglobin becomes saturated; * At muscles - low partial pressure of Oxygen/ O2/ blood - high partial pressure of O2; * Hence oxygen dissociates from haemoglobin; * Mention of myoglobin. c) * As blood leaves heart through main arteries blood pressure is high. * Blood pressure reduces as blood moves further from the heart. * This is due to larger cross-sectional area of arterioles and then capillaries. * Friction of blood against blood vessel walls reduces blood pressure. * Longer blood vessels therefore reduce blood pressure further. * Blood velocity also reduces as blood moves further from the heart. * Again, this is due to increased cross-sectional area. * However, blood velocity increases as it enters venules and veins due to decreased cross- sectional area. * Blood flows fastest in arteries due to this being smallest cross-sectional area.

When competing at maximum effort a performer will experience changes in the way that blood is distributed around the body compared to when at rest. a) Explain why the blood flow to the brain remains the same at rest and during the game. (2 marks) b) Explain why there is a need for blood flow to increase to the skeletal muscles during the game and how this is achieved. (4 marks) a) * Brain requires a constant supply of oxygen. * This cannot be changed during exercise as the body cannot function without the brain functioning effectively. b) * To supply exercising muscles with oxygen and nutrients. * To remove carbon dioxide / waste products. * Achieved by vasodilation of arteries supplying muscles. * And vasoconstriction of arteries to other areas of the body. * Caused by sympathetic nerves.