AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
During sudden vigorous activity, the muscle cells may have to work without sufficient oxygen. In such anaerobic conditions, glucose is broken down to lactic acid instead of being fully oxidised. The build-up of lactic acid in the muscles causes cramps.
Source: Chapter 6 (Life Processes context — anaerobic respiration in muscles)
This question is from the Life Processes / respiration topic, not from the Chapter 6 coordination passages provided. The examiner expects you to state: (1) insufficient oxygen supply during vigorous activity → anaerobic respiration occurs → (2) lactic acid accumulates in muscles → (3) causes cramps. These three points earn the 2 marks. Avoid confusing this with the nervous/hormonal coordination topic.