**Question:** Among the following nerve fibres the one with lower conduction velocity is:

A. Unmyelinated C fibres
B. Myelinated Aδ fibres
C. Myelinated Aα fibres
D. Myelinated Aβ fibres

**Core Concept:**

The conduction velocity of a nerve fibre is determined by the diameter of the fibre, the myelination, and the number of axons in the fibre. Myelination helps in faster conduction by reducing the electrical resistance along the axon. Unmyelinated fibres have lower conduction velocities compared to myelinated fibres.

**Why the Correct Answer is Right:**

In this question, we are comparing nerve fibres based on their conduction velocity. The correct answer, A (unmyelinated C fibres), represents a type of nerve fibre that has a lower myelination and, consequently, a lower conduction velocity compared to the other choices.

**Why Each Wrong Option is Incorrect:**

B (myelinated Aδ fibres) is incorrect because they are myelinated and have higher conduction velocities compared to unmyelinated fibres.

C (myelinated Aα fibres) is incorrect because they are myelinated and have higher conduction velocities compared to unmyelinated fibres.

D (myelinated Aβ fibres) is incorrect because they are myelinated and have higher conduction velocities compared to unmyelinated fibres.

**Clinical Pearl:**

Understanding the conduction velocity of different nerve fibres is crucial in clinical practice, as it helps in diagnosing and assessing neurological conditions involving peripheral nerves or neuromuscular disorders, where changes in conduction velocity can indicate disease processes or abnormalities.

In summary, the correct answer (A) unmyelinated C fibres) is chosen due to their lower myelination and, consequently, lower conduction velocities compared to the myelinated options (B-D).