Myelination and white and gray matter.

White matter

-Aggregations or bundles of myelinated and unmyelinated axons located in the brain and spinal cord. -composed primarily of myelinated axons. -The whitish color of myelin gives white matter its name. -Blood vessels are present in both white and gray matter. -In the spinal cord, the white matter surrounds an inner core of gray matter that, is shaped like a butterfly or the letter H.

What does it mean when something is myelinated?

-Axons surrounded by a multilayered lipid and protein covering are myelinated. -The sheath electrically insulates the axon of a neuron and increases the speed of nerve impulse conduction.

What type of cells are able to myelinate an axon?

-Schwann cells in the PNS. -oligodendrocytes in the CNS.

Gray Matter

-contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia. -It appears grayish because the Nissl bodies impart a gray color and there is little or no myelin in these areas. - in the brain, a thin shell of gray matter covers the surface of the largest portions of the brain, the cerebrum and cerebellum

Nerves

A bundle of axons and/or dendrites covered with connective tissue found outside the central nervous system.

Node of Ranvier

A space, along a myelinated axon, between the individual Schwann cells that form the myelin sheath and the neurolemma. Also called a neurofibral node.

What classifies unmyelinated?

Axons without a covering.

What is the functional advantage of myelination?

Myelination increases the speed of nerve impulse conduction.

Neurolemma

The peripheral, nucleated cytoplasmic layer of the Schwann cell. Also called sheath of Schwann (SCHVON).

ganglion

Usually, a group of neuronal cell bodies lying outside the central nervous system (CNS).