Nerve Fibers

• 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:

A Fibers:

• 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).

B Fibers:

• Myelinated with a smaller diameter (1-3 micrometers).
• Involved in transmitting autonomic nervous system signals, regulating involuntary functions like heartbeat and digestion.

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 fiber:

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.

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.

Conduction velocity:

• The speed at which electrical signals are transmitted along nerve fiber 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.

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.

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