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Answer the following questions… • During a practice session, blood flow is redirected to the active muscles. Explain how this is achieved. (3 marks) Answers 1. Increased metabolic activity / increased carbon dioxide / increased lactic acid / drop in pH; 2. Detected by chemoreceptors 3. Message to medulla / vasomotor control centre 4. Sympathetic nerve impulse to blood vessels 5. Adrenaline / Noradrenaline is produced 6. Pre-capillary sphincters at capillaries 7. Vasoconstriction (in blood vessels)/ preventing blood flow to muscles / organs not required 8. Vasodilatation (in blood vessels) / blood vessels open to allow increased blood flow to the muscle (3 marks) Lung Capacities and Volumes Volumes at Rest • The tidal volume (TV), about 500 mL, is the amount of air inspired during normal, relaxed breathing. • The inspiratory reserve volume (IRV), about 3,100 mL, is the additional air that can be forcibly inhaled after the inspiration of a normal tidal volume. • The expiratory reserve volume (ERV), about 1,200 mL, is the additional air that can be forcibly exhaled after the expiration of a normal tidal volume. • Residual volume (RV), about 1,200 mL, is the volume of air still remaining in the lungs after the expiratory reserve volume is exhaled. Volumes at Rest • Vital Capacity (VC), about 4800mL, is the maximal amount of air exhaled after a maximal inspiration. – Which 3 lung volumes combine to create VC? • Total Lung Capacity (TLC), about 6000mL is vital capacity plus residual volume. Minute ventilation • The amount of air taken into or out of the lungs in one minute. • Frequency x tidal volume Volumes During Exercise • Using page 32 of your text book, complete the table to show what happens to lung capacities during exercise. Long Term Effects of Exercise • Aerobic exercise has little impact on Lung capacity. Partial Pressure • Pressure of O2 is high in the lungs compared to the pressure of O2 of the blood in the pulmonary artery (that flows into the alveoli). • The difference in pressure is called a concentration gradient. • The concentration gradient allows diffusion (movement of gases) to occur. Partial Pressure • Diffusion only occurs from areas of high pressure to areas of low pressure (its moving down the gradient). • Oxygen diffuses from the alveoli into the capillaries (down the concentration gradient). • The oxygen combines with haemoglobin (in the RBCs) in the blood to form oxyhaemoglobin. Gaseous Exchange • When blood arrives to the muscle cell via the capillaries, there is another concentration gradient. • During exercise, this concentration gradient is steeper than at rest due to the higher levels of O2 being used by the cell (and thus more CO2). • The steeper the gradient, the faster O2 diffuses into the muscle cell. Gaseous Exchange • In order for O2 to be given to the muscle cells, it must dissociate with the haemoglobin. • As body temperature rises, dissociation occurs more readily. • A drop in pH (due to increase in lactic acid) also causes dissociation to occur more readily. Gaseous Exchange • Haemoglobin has a higher affinity for CO2 than O2. • So the increase of CO2 during exercise causes O2 to dissociate rapidly. • The same process of gaseous exchange occurs with CO2 due to the difference in pressures of CO2 between the muscle cells and capillaries, creating a concentration gradient. Partial Pressure at Altitude • At altitude there is lower pressure of O2 in the alveoli. • This means there is a reduction in the concentration gradient. • Therefore, less oxygen is diffused into the blood and there is less O2 picked up by the haemoglobin. • This results in less O2 being transported in the body. Partial Pressure at Altitude • When we are exposed to high altitude, our body responds by increasing our breathing rate (and heart rate) in an attempt to get more O2 into the body. • This is not efficient, so our body needs to adapt to our environment. • The body begins to increase RBC production, which means more haemoglobin molecules available to associate with O2. • Therefore, more O2 is transported around the body. Altitude Training • Is the deliberate attempt to increase RBC production to gain an advantage in aerobic based sports. • It is widely used by many athletes but particularly by long and middle-distance event athletes. • Athletes will train at altitude for a number of weeks to increase RBC production before returning to sea level and competing, where an increased no. of RBCs will improve their VO2max. Altitude Training • It is important to be at altitude for a number of weeks prior to competition as initially, exercising at altitude is very difficult. • This is due to the lower pressure of O2 and less O2 being pumped around the body. • Therefore, the body must work a lot harder to get the same results experienced during training at sea level. • In the first few weeks of being at altitude the body is more reliant on the anaerobic system and therefore fatigue sets in quickly due to the production of lactic acid.