Image of a growth cone (red) extending from an axon (green).

A growth cone is a dynamic, actin-supported extension of a developing axon seeking its synaptic target. Their existence was originally proposed by Spanish histologist Santiago Ramón y Cajal based upon stationary images he observed under the microscope. An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... Actin (red) profilin (blue) complex. ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... Illustration of the major elements in a prototypical synapse. ... A thin section of lung tissue stained with hematoxylin and eosin. ... Santiago Ramón y Cajal Santiago Ramón y Cajal (May 1, 1852 – October 17, 1934), Nobel laureate, 1906, was a Spanish histologist and is considered to be the father of modern neuroscience. ... It has been suggested that microscopy be merged into this article or section. ...

Structure

The morphology of the growth cone can be easily described by using the hand as an analogy. The fine extensions of the growth cone are known as "filopodia". The filopodia are like the "fingers" of the growth cone; they contain actin filaments that give them shape and support. In between filopodia--much like the webbing of the hands--are the "lamellipodia". The filopodia contain receptors that are important for axon guidance. In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ... Axon guidance (also called axon pathfinding) is a subfield of neural development concerning the process by which neurons send out axons to reach the correct targets. ...

Movement

The growth cones are continually being built up through construction of the actin microfilaments and extension of the plasma membrane via vesicle fusion. Laminins of the basal membrane interact with the integrins of the growth cone to promote the forward movement of the growth cone. Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ... Laminins are a family of heterotrimeric glycoproteins found in the basal lamina underlying epithelia. ... The basal lamina (often erroneously called basement membrane) is a layer on which epithelium sits. ... An integrin, or integrin receptor, is an integral membrane protein in the plasma membrane of cells. ...

Axon guidance

Growth cone receptors detect the presence of chemical gradients of axon guidance molecules such as ephrins and semaphorins. These gradients will either attract or repel the growth cone, thus helping to guide the axon away from certain paths and attracting them to their proper target destinations. This mechanism is what underlies the initial wiring of the nervous system.

Reference

• Kandel ER, Schwartz JH, Jessell TM 2000. Principles of Neural Science, 4th ed. pp.1070-1074. McGraw-Hill, New York. ISBN 0838577016