CIE IGCSE Biology: 复习笔记：9.1.9 Explaining the Effect of Physical Activity on Heart Rate: Extended

• So that sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen for increased respiration
• An increase in heart rate also allows for waste products to be removed at a faster rate
• Following exercise, the heart continues to beat faster for a while to ensure that all excess waste products are removed from muscle cells
• It is also likely that muscle cells have been respiring anaerobically during exercise and so have built up an oxygen debt
• This needs to be ‘repaid’ following exercise and so the heart continues to beat faster to ensure that extra oxygen is still being delivered to muscle cells
• The extra oxygen is used to break down the lactic acid that has been built up in cells as a result of anaerobic respiration

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