Final answer:
The duration of anesthesia with 2% lidocaine 1:100,000 epinephrine as a nerve block is 60 minutes. It achieves numbness by blocking sodium channels required for nerve impulse transmission.
Step-by-step explanation:
The anesthetic effect on soft tissue when using 2% lidocaine 1:100,000 epinephrine as a nerve block is generally 60 minutes. Lidocaine, a local anesthetic, operates by inhibiting voltage-gated sodium channels, which are crucial for the propagation of nerve impulses. When these sodium channels are blocked, the nerve is unable to transmit signals for sensation, including pain, which results in numbness in the area where the lidocaine has been applied. The addition of epinephrine constricts local blood vessels, reducing bleeding in the area and slowing the absorption of lidocaine into the bloodstream, thus slightly prolonging its anesthetic effect.
Neurons transmit information through a complex process starting with the initiation of an electrical impulse, which travels along the neuron's axon. This electrical signal, known as an action potential, is generated by the flow of ions, specifically sodium and potassium, across the neuronal membrane. Local anesthetics like lidocaine block the flow of sodium, thereby inhibiting the generation and propagation of action potentials and preventing the transmission of sensory signals to the brain. This explains why these drugs are effective in producing a reversible loss of sensation.