Practice Questions

1.During exercise both heart rate and breathing rate increase.Explain why

During exercise muscles respire more to release energy for muscle contraction.

The heart rate increases to pump more oxygenated blood to the muscles, supplying more oxygen and glucose. Breathing rate increases to take in more oxygen and remove more carbon dioxide. This allows aerobic respiration to continue in the muscles.

2.Describe two changes in breathing during exercise.

Breathing rate increases (more breaths per minute).

Breath volume (tidal volume) increases (more air taken in with each breath).

3. Explain why muscles become fatigued during long periods of vigorous exercise.

During long periods of vigorous exercise the supply of oxygen to the muscles becomes insufficient.

As a result, muscles carry out anaerobic respiration. This produces lactic acid, which builds up in the muscles. The lactic acid lowers pH and interferes with enzyme activity, causing the muscles to become fatigued and contract less efficiently.