myelin sheath
The sheath of Schwann is also called the myelin sheath. It is a layer of fatty material that surrounds and insulates nerve fibers, allowing for faster transmission of nerve impulses.
The Schwann cell forms a myelin sheath around the axon of the nerve.
myelin sheath peace.love.faith
Surrounding the myelin sheath, there is a thin membrane called neurilemmal sheath. This is also called neurilemma or sheath of Schwann. This contains Schwann cells, which have flattened and elongated nuclei. The cytoplasm is thin and modified to form the thin sheath of neurilemma enclosing the myelin sheath. One nucleus is present in each internode of the axon. The nucleus is situated between myelin sheath adn neurilemma. At the node of Ranvier (where myelin sheath is absent), the neurilemma invaginates and runs up to axolemma in the form of a finger like process. In nonmyelinated nerve fiber, the neurilemma continuously surrounds axolemma. Neurilemma is absent in central nervous system. Neurilemma is necessary for the formation of myelin sheath (myelinogeneis).
Its the Neurilemma.
Schwann cells form a myelin sheath around peripheral nerve fibers in the peripheral nervous system.
Myelin Sheath Cytoplasm Dendrites Cell Body
Neurilemma
another name for the sheath of schwann is neurilemma.
The cells that are thought to enable myelination to take place are called Glial Cells, which wrap themselves around the axions in a spiral fashion. This creates a sheath, or insulation, around the axion. It is often referred to as 'White Matter'.
The formation of myelin sheath around the axon is called the myelinogenesis. In the peripheral nerve, the myelinogenesis starts at 4th month of intrauterine life. It is completed only in the second year after birth. Before myelinogeneis, Schwann cells of the neurilemma are very close to axolemma as in the case of unmyelinated nerve fiber. The membrane of the schwann cell is double layered. The schwann cells wrap up and rotate around the axis cylinder in many concentric layers. The concentric layers fuse to produce the myelin sheath but the cytoplasm of the cells is not deposited. Outermost membrane of Schwann cell remains as neurilemma. Nucleus of these cells remains in between myelin sheath and neurilemma. In the central nervous system, the schwann cells are absent and the myelin sheath is formed by the neuroglial cells called the oligodendroglia.
When the peripheral nervous system develops, Schwann cells line up along unmyelinated axons at regular intervals that eventually become the nodes of Ranvier (important for saltatory nerve condution). The ensheathing process takes place as Schwann cells wrap around the axon many times over, creating concentric layers whose cytoplasm progressively condenses. Contact with the axons also activates myelin genes leading to the expression of myelin glycoproteins and lipids across the Schwann cell plasma membrane. The sheath therefore consists of plasma membrane, cytosol, lipids, glycoproteins, and the Schwann cell nucleus.*So basically, the schwann cells is a protective membrane that covers the axon. It also produces myelin sheath (the coating of a neuron), which increases the speed of the nerve impulse.