Pharmacology - Local Anaesthetics

Question 1

Describe the mechanism of action of local anaesthetics

Answer 1

1. Blocking Sodium (Na⁺) Channels
   Nerve impulses (action potentials) depend on the influx of sodium ions through voltage-gated Na⁺ channels.

Local anaesthetics bind to and block these channels in the neuronal membrane.

2. Preventing Depolarisation
   Without Na⁺ influx, the nerve cannot depolarise, so it cannot generate or propagate an action potential.

This stops transmission of pain signals to the brain.

Question 2

Where do local anaesthetics work?

Answer 2

LA targets peripheral nerves, specifically the axon of sensory or motor neurons

Question 3

Describe the order of nerve blockade

Answer 3

Smaller and less myelinated fibres are blocked first

1) C fibres - Pain, temperature

2) A-delta fibres - Sharp pain

3) A-beta fibres - Touch, pressure

4) A-alpha fibres - Motor