Types of Nerve Fibres and their Functions – Local and General Anaesthesia

Action and Functions of Nerve Fibres is very important in understanding their action and the use of Local and General Anaesthetics in controlling Pain, Proprioception, Touch and Pressure. Each Nerve Fibre has a specific function and the Anaesthetic agents should be such that they act on those nerve fibres to get the desired effect.

It is important to note that the diameter of the Nerve Fibre plays an important role in transmission speed of nerve impulse. The Larger the Diameter of Nerve Fibre the Higher the Speed of Conduction.  A-Fibres are the largest in Diameter and have the fastest speed of conduction at 70-120 m/sec

Nerve Fibres and their Function and Conduction

In Local Anaesthesia the A-Delta fibres are targeted to stop pain transmission.

The action of Various Nerve Fibres:

A Fibres: These have Motor Function in Muscle Spindles

A – Alpha Fibres: Motor Function

  • A-Alpha Type Ia – Proprioception
  • A-Alpha Type Ib – Proprioception

A – Beta Fibres: Also called as Type II fibres

  • Touch
  • Pressure
  • Proprioception

A- Delta Fibres: Also called as Type III fibres

  • Pain
  • Cold
  • Temperature
  • Touch

B Fibres: These are Preganglionic Autonomic Fibres

C Dorsal Root: Type IV Fibres

  • Pain
  • Warm and Cold temperature
  • Touch

C Sympathetic Fibres: These are Post ganglionic sympathetic fibers


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