In denervated muscle, the rheobasic current is typically provided by which type of current?

• A. Galvanic
• B. Faradic
• C. Sine
• D. Static

Answer: (A)

In denervated muscle, contraction must be produced by directly depolarizing the muscle fiber membrane because there is no intact nerve to carry a stimulus. The rheobase is the minimum current needed when the duration is effectively infinite to evoke a response. To reliably cause contraction without nerve input, you use a direct, unidirectional, long-duration current. That is galvanic current. Other currents rely on nerve activation (Faradic) or are alternating (Sine), so they won’t reliably produce contraction in denervated muscle. Static DC is another form of direct current, but galvanic current is the standard way to provide the rheobasic current in this context.