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| ==Axon guidance== | ==Axon guidance== | ||
| Growth cone receptors detect the presence of axon guidance molecules such as ]s and ]s. These molecules 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 contributes to the initial wiring of the nervous system and is also important in ] following an injury. | Growth cone receptors detect the presence of axon guidance molecules such as netrin, slit, ]s, and ]s. It has more recently been shown that cell fate determinants such as wnt and sonic hedgehog(shh) can also act as guidance cues. These molecules 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 contributes to the initial wiring of the nervous system and is also important in ] following an injury. | ||
| ==Reference== | ==Reference== | ||
Revision as of 20:31, 25 August 2006
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.
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.
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.
Axon guidance
Growth cone receptors detect the presence of axon guidance molecules such as netrin, slit, ephrins, and semaphorins. It has more recently been shown that cell fate determinants such as wnt and sonic hedgehog(shh) can also act as guidance cues. These molecules 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 contributes to the initial wiring of the nervous system and is also important in axonal regeneration following an injury.
Reference
Gordon-Weeks, P. R. 2005. Neuronal Growth Cones, Cambridge University Press, Cambridge. ISBN, 0521 44491 8
- Kandel ER, Schwartz JH, Jessell TM 2000. Principles of Neural Science, 4th ed. pp.1070-1074. McGraw-Hill, New York. ISBN 0838577016
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