4.4.2.2 Response to Exercise

Question 1

What happens to the body during exercise?

Answer 1

• the human body reacts to the increased demand for energy
• the heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood so the muscle cells can use the oxygen to do more aerobic respiration and release more energy for contracting the muscle

Question 2

During an aerobics class, what would happen to your body temperature and breathing rate? Why?

Answer 2

• they would both increase
• these changes increase the blood flow to the muscles and so increase the supply of glucose and oxygen increasing the rate of removal of CO2
• heat is a by-product of respiration

Question 3

How can you prove you’re doing aerobic respiration?

Answer 3

limewater turns cloudy in the presence of CO2 and CO2 is a product of aerobic respiration

Question 4

When does anaerobic respiration take place?

Answer 4

• in hard exercise/ high-intensity activities e.g. sprinting
• if insufficient oxygen is supplied anaerobic respiration takes place in muscles
• the incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt (as oxygen is needed to break lactic acid down)
• if muscles are subjected to long periods of vigorous activity they become fatigued i.e. they stop contracting as efficiently and tiring as anaerobic respiration means less oxygen reaches the muscles cells meaning the release less energy for contraction
• one cause of muscle fatigue is build-up of lactic acid in the muscle which causes cramps
• blood flowing through the muscle removes the lactic acid by transporting the lactic acid to the liver where it is converted back into glucose

Question 5

What do endurance athletes do to prevent lactic acid build up?

Answer 5

• to prevent lactic acid build up endurance athletes limit their heart rates (pace themselves) to prevent anaerobic respiration
• to stay below the lactic aid threshold (the point where blood lactic acid concentration starts to rise)
• a build up of lactic acid would hinder their performance as it would cause fatigue causing cramps

Question 6

How is lactic acid removed?

Answer 6

blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose or oxidised to O2 and CO2

Question 7

What effect does exercise have on heart rate?

Answer 7

• increased exercise increases the pulse rate
• this is because muscles contract more which means the muscle cells do more aerobic respiration to release more energy to contract and for aerobic respiration to release more energy more oxygen and glucose needs to be supplied and CO2 needs to be removed faster by the blood which is pumped faster to the muscles to do this which increases the pulse rate

Question 8

What is needed during exercise?

Answer 8

• during exercise more energy is needed in order for the muscles to contract
• this means respiration has to occur faster and therefore more oxygen needs to be supplied to cells (and ore CO2 removed)
• this is done by:
  
  • heart rate increasing causing more oxygenated blood be transported around the body and provide muscle cells more oxygen so they can do more aerobic respirate and release more energy for contraction
  • breathing rate increasing causing the rate at which oxygen is taken into the lungs to increase meaning oxygen is transferred to the blood faster causing more oxygenated blood be transported around the body and provide muscle cells more oxygen so they can do more aerobic respiration and release more energy for contraction
  • breath volume increasing causing the volume of oxygen taken into the lungs at one point to increase causing more oxygen to be transferred to the blood at a time causing more oxygenated blood be transported around the body and provide muscle cells more oxygen so they can do more aerobic respiration and release more energy for contraction