Anaerobic respiration occurs in muscle tissue when there is not enough oxygen to support aerobic respiration. Which condition is most likely to directly result from this?

• A. Seizures
• B. Cramps
• C. Headache
• D. Dizziness

Answer: (B)

When oxygen delivery to muscle cells is insufficient for aerobic respiration, muscle fibers switch to anaerobic glycolysis to keep generating ATP. In this pathway, glucose is broken down to pyruvate and then converted to lactate, which allows glycolysis to continue but yields far less ATP. The resulting lactate accumulation lowers the internal pH of muscle cells and irritates the muscles, producing the burning sensation and eventual cramps seen during intense effort. So cramps are the most direct consequence of anaerobic respiration in muscle tissue. Seizures, headaches, and dizziness involve other bodily systems and are not direct results of this metabolic shift in skeletal muscle.