During a full or total reaction of degeneration to a muscle following a peripheral nerve injury, which does NOT take place?

• A. The longitudinal reaction is positive
• B. There is decreased excitability
• C. There is no response to faradic stimulation
• D. The chronaxie is decreased

Answer: (D)

When a muscle undergoes full degeneration after a peripheral nerve injury, it becomes denervated and its electrical excitability declines. This shows up as a reduced or absent response to nerve-based stimulation, such as faradic current, because the nerve connection that normally carries the impulse is lost. The muscle membrane also requires a longer pulse to reach threshold, so chronaxie tends to increase rather than decrease. Therefore, the idea that chronaxie is decreased does not occur in this degenerated state. The other aspects—reduced excitability and no response to faradic stimulation—fit with complete degeneration, while the notion of a decreased chronaxie would imply greater excitability, which is not what happens here.