Anesthetics and Nerve Transmission

Anesthetics and Nerve Transmission

Local anesthetics block voltage-gated Na+ channels. General anesthetics are thought to activate chemically Cl- gated channels, thereby rendering the nervous system quiescent while surgery is performed.

• What specific process do anesthetics impair, and how does this interfere with nerve impulse transmission?

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APA

Anesthetics and Nerve Transmission

Anesthetics, both local and general, impair the electrophysiological processes required for nerve impulse transmission. They achieve this by blocking or modifying ion channel activity, thereby disrupting action potential generation and propagation.

1. Process Impaired by Anesthetics

Anesthetics interfere with action potential formation and conduction, which are essential for nerve signal transmission. They primarily target the voltage-gated Na⁺ (sodium) channels and chemically gated Cl⁻ (chloride) channels, depending on whether they are local or general anesthetics.

2. How This Interferes with Nerve Impulse Transmission

A. Local Anesthetics and Voltage-Gated Na⁺ Channels

• Mechanism: Local anesthetics (e.g., lidocaine, bupivacaine, procaine) bind to and block voltage-gated Na⁺ channels in sensory neurons.
• Effect: This prevents Na⁺ influx, which is necessary for the depolarization phase of an action potential.
• Outcome:
  • If Na⁺ channels remain blocked, the threshold potential is not reached, and an action potential cannot be generated.
  • As a result, sensory signals (including pain) are not transmitted to the central nervous system.

✅ Example: When a dentist uses lidocaine, it numbs the area by preventing pain signals from reaching the brain.

B. General Anesthetics and Chemically Gated Cl⁻ Channels

• Mechanism: General anesthetics (e.g., propofol, isoflurane, sevoflurane) enhance the activity of γ-aminobutyric acid (GABA) receptors, which are Cl⁻ ion channels.
• Effect: When activated, Cl⁻ influx hyperpolarizes the neuron, making it less excitable by increasing the resting membrane potential further from the threshold.
• Outcome:
  • The nervous system becomes quiescent, reducing motor responses, consciousness, and awareness of pain.
  • The central nervous system (CNS) is functionally inhibited, leading to unconsciousness, amnesia, and…