12 Difference Between Myelinated And Unmyelinated Nerve Fibers

Neurons are specialized cells that transmit chemical and electrical signals in the brain; they are the basic building blocks of the central nervous system. The primary components of the neuron are the soma (cell body), the axon (a long slender projection that conducts electrical impulses away from the cell body), dendrites (tree-like structures that receive messages from other neurons), and synapses (specialized junctions between neurons).

Neurons are responsible for everything from consciousness and thought to pain and hunger. There are three primary types of neuron:

1. Sensory neurons
2. Motor neurons
3. Interneurons

Some axons are covered with myelin sheath while others are not. Myelin is a fatty material that wraps around the axon to form the myelin sheath. This external coating functions as insulation to minimize dissipation of the electrical signal as it travels down the axon. Myelin’s presence on the axon greatly increases the speed of conduction of the electrical signal, because the fat prevents any electricity from leaking out. This insulation is important, as the axon from a human motor neuron can be as long as a meter—from the base of the spine to the toes. Periodic gaps in the myelin sheath are called nodes of Ranvier. At these nodes, the signal is “recharged” as it travels along the axon.

The Nerve fibers that are insulated by a myelin sheath are generally referred to as Myelinated Nerve Fibers whereas those that do not have a myelin sheath are referred to as unmyelinated Nerve Fibers/Neurons. Typically, the myelin sheath is not actually part of the neuron but an insulation component. Myelinated nerve fibers occur in the white matter of the brain, spinal cord and in the central and cranial nervous system. On the other hand, Unmyelinated neurons can be found in both the peripheral and central nervous system in the group c nerve fibers, responsible for transmission of secondary pain or itch.

Characteristics Myelinated Nerve Fibers

• Myelinated Nerve Fibers are nerve fibers that are insulated by a myelin sheath.
• The nerve fibers with long axons are myelinated.
• The axis cylinder of the myelinated nerve fibres has two sheaths.
• Myelinated fibres show nodes and internodes.
• The myelinated nerve fibers appear white in color.
• The myelinated nerve fibers have nodes of Ranvier.
• The Schwann cells wrap tightly around the nerve axon and form the myelin sheath.
• Due to presence of nodes of Ranvier on myelinated nerve fibers, the speed of transmission of nerve impulses is high in myelinated nerve fibers. 
• Most neurons in the central and peripheral nervous system are myelinated because they require fast conduction speed such as neuron involved in spinal reflexes.
• Myelinated nerve fibers occur in the white matter of the brain, spinal cord and in the central and cranial nervous system.
• Due to presence of myelin sheath, myelinated nerves do not lose the impulse during conduction.
• In myelinated fibers electrical impulses (action potentials) travel as continuous waves.
• Myelinated nerve fibres may give off collateral nerve fibres.

Characteristics Unmyelinated Nerve Fibers

• Unmyelinated nerve fibers are nerve fibers that do not have a myelin sheath.
• The short axon nerve fibers are unmyelinated.
• The axis cylinder of unmyelinated nerve fibres has only one sheath.
• Unmyelinated nerve fibres do not show notes and internodes.
• The nerve fibers appear gray in color.
• Schwann cells are not wound around the axons but simply form a groove.
• They do not have nodes of Ranvier.
• They do not have myelin insulations, and therefore, the speed of the transmission of the nerve impulses is low.
• Unmyelinated neurons can be found in both the peripheral and central nervous system in the group c nerve fibers, responsible for transmission of secondary pain or itch.
• Unmyelinated nerve fibers can lose the nerve impulse during conduction.
• In Unmyelinated fibers electrical impulses (action potentials) ”hop” or propagate by saltatory conduction.
• Collateral fibres are not produced in Unmyelinated nerves.

Difference Between Myelinated And Unmyelinated Nerve Fibers In Table Form