Final answer:
Lidocaine is less effective in inflamed tissue due to acidity; it acts as a Na+ channel blocker to halt nerve impulse transmission, thus causing numbness and preventing pain signals from reaching the brain.
Step-by-step explanation:
Lidocaine is less effective in inflamed tissue, where the acidic environment caused by inflammation can reduce the effectiveness of the local anesthetic. Drugs such as lidocaine, and similar anesthetics like novocaine, act as Na+ channel blockers. These voltage-gated sodium channels are essential for the initiation and transmission of nerve impulses. When lidocaine blocks these channels, it prevents sodium ions from entering neurons, which stops the propagation of the pain signal. This action renders lidocaine an effective local anesthetic because it produces numbness and pain relief by inhibiting neural signal transmission.
The absence of pain due to lidocaine is a result of its impact on signal reception and transduction in neurons. With the voltage-gated sodium channels blocked, nerve cells cannot depolarize and transmit pain signals to the brain, leading to a temporary loss of sensation in the treated area.