myelin

(noun)

A white, fatty material composed of lipids and lipoproteins that surrounds the axons of nerves and facilitates swift neural communication.

Related Terms

(noun)

A white, fatty material composed of lipids and lipoproteins that surrounds the axons of nerves and facilitates swift communication.

Related Terms

Examples of myelin in the following topics:

  • Introducing the Neuron

    • Some axons are covered with myelin, a fatty material that wraps around the axon to form the myelin sheath.
    • Periodic gaps in the myelin sheath are called nodes of Ranvier.
    • The myelin sheath is not actually part of the neuron.
    • Myelin is produced by glial cells (or simply glia, or "glue" in Greek), which are non-neuronal cells that provide support for the nervous system.
    • This neuron diagram also shows the oligodendrocyte, myelin sheath, and nodes of Ranvier.

  • Stages of the Action Potential

    • In unmyelinated axons (axons that are not covered by a myelin sheath), this happens in a continuous fashion because there are voltage-gated channels throughout the membrane.
    • In myelinated axons (axons covered by a myelin sheath), this process is described as saltatory because voltage-gated channels are only found at the nodes of Ranvier, and the electrical events seem to "jump" from one node to the next.
    • Damage to the myelin sheath from disease can cause severe impairment of nerve-cell function.

  • Cognitive Development in Childhood

    • Glial cells, which account for half of all brain mass in early childhood, are responsible for a process known as myelination.
    • The connection between neighboring neurons (which is made smoother through myelination) allows for advanced brain function, such as planning and implementing behaviors and integrating sensory information from the environment.
    • Due to synaptic pruning, myelination, and a child's environmental experiences, the developing brain will grow from 30 percent of its adult weight at birth to 70 percent by age 2.

  • Cerebral Cortex

    • It contains glial cells, which guide neural connections, provide nutrients and myelin to neurons, and absorb extra ions and neurotransmitters.
    • Gray matter is the mass of all the cell bodies, dendrites, and synapses of neurons interlaced with one another, while white matter consists of the long, myelin-coated axons of those neurons connecting masses of gray matter to each other.

  • Neural Networks

    • Some axons are encased in a lipid-coated myelin sheath, making them appear a bright white; others that lack myelin sheaths (i.e., are unmyelinated) appear a darker beige color, which is generally called gray.