神经连接的形成

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神经元的发育：• 外胚层细胞形成神经元，神经嵴或者

表皮• 什么类型的神经元• 神经元的靶细胞

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外胚层

神经管

神经元

运动神经元

BMP（－）

Notch/Delta

Shh

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hox

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Hox and Lim

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神经元连接聚焦到两个主要的系统：• 运动神经元——其轴突从脊髓出发到达特

定的肌肉• 视觉系统——轴突从视网膜出发到达脑

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• 1. Pathway selection, wherein the axons travel along a route that leads them to a particular region of the embryo

• 2. Target selection, wherein the axons, once they reach the correct area, recognize and bind to a set of cells with which they may form stable connections

• 3. Address selection, wherein the initial patterns are refined such that each axon binds to a small subset (sometimes only one) of its possible targets

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Pathway selection

Cell adhesion and contact guidance by attractive and permissive molecules

轴突生长锥最初的路径是由其细胞外的环境决定的。

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Guidance by specific growth cone repulsion

ephrins and semaphorins

ephrins

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12

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Guidance by diffusible molecules

1 Neterin and their receptors

联合神经元是一种中间 神经元

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Transformed chick fibroblast (COS) cells secreting netrins elicit axon outgrowth of commissural neuronsfrom 11 -day embryonic rat dorsal spinal cord explants.

dorsal spinal cord explants.

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2 Slit AND Robo

In Drosophila, Slit is secreted by the neuralcells in the midline; growth cones of Drosophila neurons express a Roundabout (Robo)

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Midline neurons

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commissural neurons?

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Target selection

Neurotrophins: nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophins 3 and 4/5 (NT3, NT4/5).

sensory neurons from the rat dorsal root ganglia& NT3

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Forming the synapse: Activity-dependent development

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"address selection"

competition

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Differential survival after innervation:Neurotrophic factors

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神经突起的发育

轴突和树突的生长 发育期间突触连接形成 突触连接的重排及精细化

总结