In pain pathways the smaller primary unmyelinated fibres are called:

 # In pain pathways the smaller primary unmyelinated fibres are called:

 A. A fibres. 

B. B fibres. 

C. C fibres. 

D. D fibres.

The correct answer is:

C. C fibres

Explanation: C fibres are small, unmyelinated nerve fibers that conduct pain signals slowly. They are primarily responsible for transmitting dull, burning, or aching pain (slow pain) and are involved in the prolonged, less localized pain sensation.

A fibres: Include A-delta fibers, which are myelinated and transmit sharp, localized pain quickly (fast pain).

B fibres: Small, myelinated fibers mainly involved in autonomic functions.

D fibres: This category does not exist in standard nomenclature for nerve fibers.