Final answer:
Local anesthetics like lidocaine and novocaine act as Na* channel blockers, preventing sodium from moving across the neuronal membrane and inhibiting the transmission of nerve impulses. This makes them effective local anesthetics.
Step-by-step explanation:
Local anesthetics like lidocaine and novocaine act as Na* channel blockers, preventing sodium from moving across the neuronal membrane. This effect makes them effective local anesthetics because it inhibits the transmission of nerve impulses, leading to numbness and loss of sensation in the area where the drug is applied.