C fibers

C Fibers

C fibers are a type of nerve fiber found in the peripheral nervous system. They are unmyelinated, which means they lack the myelin sheath that surrounds other types of nerve fibers, such as A fibers. This lack of myelination results in slower conduction velocities, making C fibers responsible for transmitting slower, chronic pain signals and other sensory information.

Structure

C fibers are small in diameter, typically ranging from 0.2 to 1.5 micrometers. Due to their unmyelinated nature, they conduct nerve impulses at a slower rate, approximately 0.5 to 2 meters per second. This is significantly slower compared to myelinated fibers, which can conduct impulses at speeds up to 120 meters per second.

Function

C fibers are primarily involved in the transmission of pain and temperature sensations. They are responsible for conveying dull, aching, and chronic pain, as opposed to the sharp, acute pain transmitted by A-delta fibers. In addition to pain, C fibers also play a role in transmitting sensations of warmth and certain types of touch.

Role in Pain Perception

C fibers are activated by a variety of stimuli, including mechanical, thermal, and chemical stimuli. When activated, they release neurotransmitters such as substance P and calcitonin gene-related peptide (CGRP), which contribute to the sensation of pain and the inflammatory response. The slow conduction of C fibers is associated with the delayed, lingering pain that often follows an initial sharp pain.

Clinical Significance

Understanding the function of C fibers is crucial in the study of pain management and treatment. Conditions such as neuropathic pain, fibromyalgia, and chronic pain syndromes often involve dysfunction or hyperactivity of C fibers. Treatments targeting C fiber activity, such as certain analgesics and nerve blocks, are used to alleviate chronic pain.

Also see

• Nociceptor
• A-delta fiber
• Pain management
• Peripheral nervous system
• Neurotransmitter