The spaces along the axon and between the myelin sheath are known as the nodes of Ranvier. They are responsible for speeding up the signals that are transmitted along the axon of the nerve. While the myelin sheath consists of many layers that protect the axon, the nodes of Ranvier are uncovered, giving them the ability to produce an electrical charge.
there are specialized cells in the nervous system produce and form the myelin in the central nervous system (brain & spinal cord) by oligodendrocytes in the peripheral nervous system by schwann cells
Remember that the Schwann cells are made of myelin sheath which insulate the impulse, but also block the sodium ion/potassium ion channels. Therefore there has to be a point where the action potential 'jumps' to, and these are the gaps between the Schwann cells, they are called the Nodes of Ranvier.
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.
Theodor Schwann was a German physiologist who discovered Schwann Cells also known as neurolemmocytes. He's also credited with discovering pepsin and inventing the term metabolism.
wherever the Schwann cells wrap around the axon, the sodium and potassium ions cannot cross the membrane; the Schwann cells wrap too tightly around the axonal membrane for there to be any extracellular space underneath them. Therefore, the only place that an action potential can occur is at the node of Ranvier-- the space between the Schwann cells. Because of this, the action potential seems to jump from node to node along the axon. "Jumping" is what the word "saltatory" means.
oligodendrocytes
They are called oligodendrocytes but in the peripheral nervous system you would call them schwann cells.
1) starting with the obvious; oligodendrocytes myelinate axons in the CNS whereas schwann cells myelinate axons in the PNS 2) a single oligodendrocyte is able to myelinate multiple axons whereas a schwann cell can only myelinate a single axon. 3) schwann cell myelination allows for axonal grown and regeneration where as oligodendrocytes inhibit axonal growth and regeneration. 4).... and probably a bunch more differences
myelin sheath
Oligodendrocytes are glial cells that function in the CNS--the brain and spine. They provide insulation (myelin sheaths) in several locations, possibly multiple neurons. Meanwhile, schwann cells are glial cells that function in the PNS--peripheral nervous system, everything outside the brain and spine. Individually, they wrap around axons of nerves, forming individual segments of myelin sheaths. They, unlike oligodendrocytes, can guide repairs to damaged axons. Damage to the nerves in the brain are not so easily remedied.
Schwann cells and oligodendrocytes
Schwann cells are functionally similar to oligodendrocytes in the central nervous system. They both provide support and insulation to nerve fibers by forming a myelin sheath around them, which helps in the transmission of nerve signals. Schwann cells are found in the peripheral nervous system while oligodendrocytes are found in the central nervous system.
Oligodendrocytes and Schwann cells both produce myelin. Oligodendrocytes produce myelin in the CNS, whereas Schwann cells produce myelin in the PNS. CNS refers to central nervous system PNS refers to peripheral nervous system
oligodendrocytes for C.N.S. and shcwann cells for P.N.S.
Myelin is a lipid insulation produced by the cells called oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. It wraps around nerve fibers to help speed up the transmission of electrical impulses along the nerve cells.
CNS: oligodendrocytes make the myelin, they cooperate in the formation of a myelin sheath along the axon, this is the process of myelination. Each oligodendrocyte produces segments of several axons.PNS: schwann cells make the myelin, each schwann cell can myelinate one segment of a single axon and they work together ot form the myelin sheath.
The glial cells: oligodendrocytes for central nervous system and schwann cells for peripheral nervous system.