Identify and describe Why Heart Rate Increases During Exercise, Changes in Breathing During Exercise and Aerobic Respiration in Exercising Muscles in the context of response to exercise.
BEEZYREVISOR
GCSE Biology Revision
Learn it. Recall it. Revise it.
GCSE Biology revision
Response to exercise
Respiration
Your specification
AQA student objectives
Learning pathway
All · Most · Some
Explain the relationships between Why Heart Rate Increases During Exercise, Changes in Breathing During Exercise and Aerobic Respiration in Exercising Muscles and how they contribute to response to exercise.
Apply and analyse knowledge of Why Heart Rate Increases During Exercise, Changes in Breathing During Exercise and Aerobic Respiration in Exercising Muscles to interpret unfamiliar information about response to exercise.
Revision summary
Key knowledge
Read on screen, then print for Cornell-style active revision.
Why Heart Rate Increases During Exercise
- When you begin to exercise, your heart rate increases to pump more blood to the working muscles.
- A higher heart rate supplies more oxygen and glucose to respiring tissues, enabling greater energy release.
- Increased blood flow also helps remove lactic acid that builds up in muscles during intense exercise.
Changes in Breathing During Exercise
- Breathing rate increases during exercise, meaning more breaths are taken per minute to supply extra oxygen.
- The volume of each breath also increases, so more air (and therefore oxygen) enters the lungs with each breath.
- Together, a higher breathing rate and greater breath volume ensure a much larger supply of oxygen reaches the muscles.
Aerobic Respiration in Exercising Muscles
- Aerobic respiration uses oxygen and glucose to release energy, and is the preferred method during exercise.
- The word equation for aerobic respiration is: glucose + oxygen carbon dioxide + water (+ energy).
- Increased heart rate and breathing rate work together to maintain the oxygen and glucose supply needed for aerobic respiration.
Anaerobic Respiration When Oxygen is Insufficient
- When muscles work so hard that oxygen cannot be delivered fast enough, anaerobic respiration takes place instead.
- Anaerobic respiration involves the incomplete oxidation (breakdown) of glucose, releasing much less energy than aerobic respiration.
- The word equation for anaerobic respiration in animals is: glucose lactic acid.
Effects of Lactic Acid on Muscles
- Lactic acid is slightly toxic and builds up in muscles during anaerobic respiration, causing several negative effects.
- It causes muscle fatigue, making the muscles feel tired and less able to continue working.
- Lactic acid also causes muscles to contract less efficiently compared to when they are working aerobically.
Oxygen Debt Explained
- An oxygen debt is the amount of extra oxygen needed after exercise to react with and remove lactic acid from the cells.
- After exercise finishes, continued heavy breathing supplies the oxygen required to pay back this oxygen debt.
- Removing lactic acid is essential because it is the cause of fatigue and inefficient muscle contraction.
The Role of the Liver in Removing Lactic Acid (Higher Tier)
- After intense exercise, the blood transports lactic acid away from the respiring muscles to the liver.
- In the liver, lactic acid is converted back into glucose, which can then be used in aerobic respiration.
- This process requires oxygen, which is why breathing remains elevated even after exercise has stopped.
Summary of the Body's Coordinated Response to Exercise
- Heart rate, breathing rate, and breath volume all increase together to meet the greater energy demands of exercising muscles.
- If oxygen supply is insufficient, anaerobic respiration occurs temporarily, producing lactic acid as a by-product.
- The body works to restore normal conditions after exercise by removing lactic acid and repaying the oxygen debt.