myelin sheath
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The name of the theory that Schleiden and Schwann developed is the cell theory.
Theodor Schwann was a German biologist who is known for his work in cell theory. He co-developed the cell theory, which states that all living organisms are composed of cells. Schwann specifically focused on animal cells and their structure.
The nucleus of the cell contains the genome.
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).
Myelin Sheath Cytoplasm Dendrites Cell Body
Neurilemma
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.
The name of the theory that Schleiden and Schwann developed is the cell theory.
Another name for Schwann cell is neurolemmocyte. Schwann cells are a type of glial cell that provides support and insulation to axons in the peripheral nervous system.
The Schwann cells wrap themselves tightly around the axon like a jellyroll. During the wrapping process, the cytoplasm is squeezed from between adjacent layers of the Schwann cell membranes, so that when the process is completed a tight core of plasma membrane material encompasses the axon. This wrapping is the myelin sheath. The Schwann cell nucleus and the bulk of its cytoplasm end up just beneath the outermost portion of its plasma membrane. This peripheral part of the Schwann cell and its exposed plasma membrane is the neurilemma.
Schwann
The German biologist Theodor Schwann (1810-1882) is considered a founder of the cell theory.
A schwann cell are supporting cells of the peripheral nervous system, they wrap themselves around nerve axons.
The Schwann cell forms a myelin sheath around the axon of the nerve.
Unlike oligodendrocytes Schwann cells can only myelinate one axon. But the number of Schwann cells it takes to myelinate an axon depends on the axon length as a Schwann cell only myelinates one area between pairs of Nodes of Ranvier. Think of it like a string of sausage. the sting is the axon, each sausage is where a single Schwann cell myelinates that axon, as stated the length will determine the total number of Schwann cells needed for myelination, but a Schwann cell can only myelinate one axon.
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The German biologist Theodor Schwann (1810-1882) is considered a founder of the cell theory.