Answer the following questions…

• During a practice session, blood flow is redirected to the active muscles. Explain how this is achieved.

(3 marks)

Answers1. 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.