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.
well, my guess is 1838, but don't take my word for it.
Schwann
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.
They are called oligodendrocytes but in the peripheral nervous system you would call them schwann cells.
yesSome brain cells are called 'schwann cells'
Adjacent cells are cells that are together, and do not have other cells between each other. A cell beside another one are together called adjacent cells, as are cells that are above or below each other and touching. So A1 and A2 are adjacent cells, as are B1 and C1. A1 and C1 are not adjacent cells as B1 is between them. A1, B1 and C1 would be adjacent cells.
gap junctions
No, the membrane protein complexes that strengthen the adhesion between adjacent cells are found in animal cells as adherens junctions and desmosomes. In plant cells, the equivalent structures are called plasmodesmata, which are channels that allow for communication between adjacent plant cells.
An adjacent group of cells are known as a range or a block. There is no particular name for a group of non-adjacent cells.
Gap junction
Anchoring junctions link intermediate filaments to adjacent animal cells, attaching the cells but still allowing movement or stretching.
Schwann cells and oligodendrocytes
This questions has been answered below in the related discussions, "what are Schwann cells"
A junction that is a protein channel linking the cytoplasms of adjacent cells is called a gap junction. This structure allows for direct communication and sharing of ions and small molecules between neighboring cells.
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.