Nerve fibers are long extensions of neurons that transmit electrical signals throughout the nervous system.
They consist of axons covered by a myelin sheath and are classified into three main types based on diameter, myelination, and conduction velocity: A, B, and C fibers.
Types of Nerve Fibers:
1. A fiber:
Myelinated with a large diameter (1-22 micrometers).
Subtypes: Aα (motor signals, proprioception), Aβ (touch, pressure, vibration), Aγ (muscle spindle regulation), Aδ (fast pain, temperature, pressure).
2. B fibers:
Myelinated with a smaller diameter (1-3 micrometers).
Involved in transmitting autonomic nervous system signals, regulating involuntary functions like heartbeat and digestion..
3. C fibers:
Unmyelinated with the smallest diameter (0.2-1.5 micrometers).
Slowest conduction, responsible for slow pain, temperature, itch sensations, and some autonomic functions..
Properties of nerve fibers:
1. Diameter:
The diameter of a nerve fiber affects the conduction velocity of the electrical signals it carries. Larger diameter fibers can transmit signals more rapidly than smaller diameter fibers.
2. Myelination:
Myelinated nerve fibers are wrapped in a fatty substance called myelin, which insulates the axon and allows for faster signal transmission. Unmyelinated nerve fibers do not have this insulation, leading to slower signal transmission.
3. Conduction velocity:
The speed at which electrical signals are transmitted along nerve fibers is called conduction velocity. This property is influenced by factors such as diameter and myelination, with larger diameter and myelinated fibers having faster conduction velocities.
4. Function:
Different types of nerve fibers are responsible for transmitting different types of sensory and motor information. This functional diversity allows the nervous system to process and transmit a wide range of information throughout the body.