A decrease in tetanic (faradic) excitability is associated with which reaction of degeneration?

• A. Accompanies partial reaction of degeneration
• B. Accompanies full reaction of degeneration
• C. Accompanies absolute reaction of degeneration
• D. Reaction of degeneration is not involved

Answer: (A)

Tetanic (faradic) excitability shows how well a muscle can keep contracting under rapid electrical stimulation. After nerve injury, the tissue goes through reactions of degeneration that describe how far the damage has progressed. In a partial reaction of degeneration, some nerve fibers are still functional while others are affected. This partial loss of function reduces the muscle’s ability to respond to high-frequency stimulation, so tetanic excitability decreases, but is not completely lost. That’s why this option is the best match. In a full reaction of degeneration, the decline would be greater, and in an absolute reaction the response would be essentially absent. The change in excitability is tied to degeneration, so it is indeed involved.