| Axons |
Articles about Axon |
Information AboutAxons |
| CATEGORIES ABOUT AXON | |
| neurons | |
| neurophysiology | |
| neuroanatomy | |
|
In s ensheathing Peripheral neurons and Oligodendrocyte s insulating those of the Central Nervous System . Along myelinated nerve fibers, gaps in the sheath known as Nodes Of Ranvier occur at evenly-spaced intervals, enabling an especially rapid mode of electrical impulse propagation called Saltation . The demyelination of axons is what causes the multitude of neurological symptoms found in the disease Multiple Sclerosis . The axons of some neurons branch to form Axon Collateral s, along which the bifurcated impulse travels simultaneously to signal more than one other cell. GROWTH & DEVELOPMENT Growing axons move through their environment via the Growth Cone , which is at the tip of the axon. The growth cone has a broad sheet like extension called Lamellipodia which contain protrusions called Filopodia . The filopodia are the mechanism by which the entire process adheres to surfaces and explores the surrounding environment. Actin plays a major role in the mobility of this system. Environments with high levels of Cell Adhesion Molecule s or CAM's create an ideal environment for axonal growth. This seems to provide a "sticky" surface for axons to grow along. Examples of CAM's specific to neural systems include N-CAM , neuroglial CAM or NgCAM , TAG-1 , MAG , and DCC , all of which are part of the Immunoglobulin superfamily. Another set of molecules called Extracellular Matrix Adhesion Molecule s also provide a sticky substrate for axons to grow along. Examples of these molecules include Laminin , Fibronectin , Tenascin , and Perlecan . Some of these are surface bound to cells and thus act as short range attractants or repellants. Others are difusible ligands and thus can have long range effects. Cells called Guidepost Cells assist in the guidance of neuronal axon growth. These cells are typically other, sometimes immature, neurons. HISTORY Some of the first intracellular recordings in a nervous system were made in the late 1930's by K. Cole and H. Curtis. Alan Hodgkin and Andrew Huxley also employed the Squid Giant Axon (1939) and by 1952 they had obtained a full quantitative description of the ionic basis of the action potential. Hodgkin and Huxley were awarded jointly the Nobel Prize for this work in 1963. SEE ALSO EXTERNAL LINKS
|
|
|