Many local anesthetics work by blocking voltagegated Na chan

Many local anesthetics work by blocking voltage-gated Na+ channels. A scientist applies a local anesthetic to a neuron axon in vitro, and then measures changes in axonal membrane potential in response to electrode stimulation of the membrane to threshold. How would the electrical activity of the membrane treated with anesthetic compare to an untreated axon. Explain/justify your answer. Include a graph.

Solution

Local anesthetics work by blocking voltage gated Na+ channels. The anesthetics block the membrane permeability to Na ions. The anesthetics block the increase in threshold in an axon membrane. Thus active potential gets blocked. Due to anesthesia, the negative membrane potential reaches maximum. This leads to opening and closing of Na+ channels gets reversibly modified.