The mechanism of action of local anaesthetics is that they act on Na+ channels in their :
**Core Concept**
Local anaesthetics are a class of medications that temporarily block the conduction of nerve impulses, thereby producing a loss of sensation in a specific area of the body. This is achieved through their action on voltage-gated sodium channels, which are essential for the initiation and propagation of action potentials in neurons.
**Why the Correct Answer is Right**
Local anaesthetics exert their effects by binding to the sodium channels in their open or inactivated states, thereby preventing the influx of sodium ions into the nerve cell. This blocks the depolarization phase of the action potential, which is necessary for the transmission of nerve impulses. The binding of local anaesthetics to sodium channels is mediated by their hydrophobic tails, which insert into the lipid bilayer of the cell membrane, and their hydrophilic heads, which interact with the sodium channel protein. This binding is reversible and is the primary mechanism by which local anaesthetics produce their anaesthetic effects.
**Why Each Wrong Option is Incorrect**
**Option A:** This is not a valid location for the action of local anaesthetics. While local anaesthetics do bind to sodium channels, their mechanism of action is not related to the Golgi apparatus.
**Option B:** Local anaesthetics do not act on potassium channels. Their primary mechanism of action is through the blockade of sodium channels, not potassium channels.
**Clinical Pearl / High-Yield Fact**
Local anaesthetics have a unique property called "ion channel selectivity," which allows them to preferentially bind to sodium channels over other ion channels, such as potassium channels. This property is essential for their ability to selectively block nerve impulses without affecting other cellular processes.
**Correct Answer: C**