There are two cells that are involved in the myelin sheath. One type is found in the central nervous system (CNS) and the other is in the peripheral nervous system (PNS).These are the oligodendrocytes (CNS) and Schwann cells (PNS).
Schwann cells are neuroglial cells that actually cover and insulate axons. They not only help to spend up nerve transmission, but they also feed the neuron.
myelin sheath
No, the outermost sheath of a hair is the cuticle, which is a protective layer made up of overlapping cells. The connective tissue root sheath surrounds the hair follicle and is involved in providing structural support to the hair.
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).
The myelin sheath is a structure that insulates neurons. It is made up of specialized cells called oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The myelin sheath helps to increase the speed and efficiency of nerve impulse conduction along the axon.
Schwann Cells make the myelin found in the (PNS) Peripheral Nervous System. It also helps speed up neurotransmissions. I hope this was helpful. for the central nervous system (brain & spinal cord) oligodendrocytes form the myelin.
Schwann cells are neuroglial cells that actually cover and insulate axons. They not only help to spend up nerve transmission, but they also feed the neuron.
myelin sheath
No, the outermost sheath of a hair is the cuticle, which is a protective layer made up of overlapping cells. The connective tissue root sheath surrounds the hair follicle and is involved in providing structural support to the hair.
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).
Specialized coverings of the axon include the myelin sheath, which is formed by oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The myelin sheath acts as an insulating layer that speeds up the conduction of nerve impulses along the axon. Nodes of Ranvier are gaps in the myelin sheath where action potentials are regenerated, allowing for saltatory conduction.
Schwann cells are specialized cells in the peripheral nervous system that wrap around nerve fibers to form the myelin sheath. They provide insulation and support to the nerve fibers, which helps to speed up the conduction of nerve impulses. The myelin sheath is segmented, with small gaps called nodes of Ranvier that facilitate rapid transmission of nerve signals.
The axon is surrounded by the myelin sheath, which is a fatty insulating layer that speeds up the transmission of electrical signals. Outside the myelin sheath, there are Schwann cells or oligodendrocytes (depending on the type of neuron) that help form and maintain the myelin sheath.
The myelin sheath is a structure that insulates neurons. It is made up of specialized cells called oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The myelin sheath helps to increase the speed and efficiency of nerve impulse conduction along the axon.
The myelin sheath. Due to its insulating properties, the myelin sheath prevents the movement of ions in nerve cells. Therefore nervous impulses will jump between the gaps in the myelin sheath (called the Nodes of Ranvier). This is a lot quicker than the conduction in non-myelinated nerve fibres which occurs by the movement of ions across each of the nerve cell membranes.
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.
They are more or less equally spaced. The size of the nodes span from 1–2 µm whereas the internodes can be up to (and occasionally even greater than)1.5 millimeters long, depending on the axon diameter and fiber type.