4.2.2: Response to exercise
Not started yet — this one needs some love.
During exercise, the body reacts to the increased demand for energy.
Heart rate, breathing rate and breath volume increase to supply muscles with more oxygenated blood.
If insufficient oxygen is supplied, anaerobic respiration takes place in muscles.
Incomplete oxidation of glucose causes a build-up of lactic acid and creates an oxygen debt.
During long periods of vigorous activity, muscles become fatigued and stop contracting efficiently.
(HT) Blood transports lactic acid from muscles to the liver, where it is converted back into glucose.
(HT) Oxygen debt is the amount of extra oxygen the body needs after exercise to react with accumulated lactic acid and remove it from cells.
Common exam mistakes
Do not say heart rate increases to send carbon dioxide to the muscles; CO₂ is a waste product carried away from muscles. Heart rate rises to deliver more oxygen and glucose.
Do not describe oxygen debt as the oxygen used during exercise; it is the extra oxygen needed after exercise to break down the lactic acid that built up.
Do not say lactic acid is converted back to glucose in the muscles, lungs or kidneys; it is carried in the blood to the liver and converted there. (Higher tier only.)
Do not just write tiredness for fatigue; link it to muscles stopping contracting efficiently.