发信人: fabian (fabian), 信区: Biology
标 题: Re: 一个问题
发信站: The unknown SPACE (Mon May 14 12:22:38 2001), 站内信件

Hope it's not late to answer your questions.

As you said, the movement of ions are often intermediated by ion channels,
which are basically proteins. Those ion channels can be modulated in a couple
of ways. Some of them are modulated by certain molecules, eg. Ca2+, Mg2+
transmitters. Some of them are modulated by voltage. Their probability of
being open can change dramatically when voltage across the membrane changes.
The ions move passively according to the chemical potential.

There are several other points:
1. For each individual channel, it can either be open or closed. The change
of state is not continuous. It occurs almost instantaneously, but randomly.
Usually a poisson modelis assumed. Modulation factors change the probablity
distribution of being open and being closed by changing the energy level of
open and closed state.
2. There are many channels of each type on the membrane. When certain type
of channel is open or closed by certain modulation, the dynamics is usually
exponential, as a result of counting process of poisson behavious of
invidual neurons.

So in summary, both kind of modulation exists in neurons, they are equally
important.

Also, there are active transportations of ions across the membrane, which
are the basis of membrane potential, and not belongs to the discussion above.

【 在 CiCiPizza (西门大官仍) 的大作中提到: 】
: 本人非生物专业， 尤其对神经系统的机理， 知之尤少。
: 我的一个问题是， 神经细胞之间的信息传递是怎样实现激活和抑制的？
: 我们知道， 神经细胞的表面有一些微通道， 可以有离子移动， 电
: 信号的传递是由离子移动实现的。(?) 根据电学的一些基本原理， 电流
: 信号（ 离子流动） 的强弱可以由两种方式来实现： 一是增加/减弱电压， 即
: 增加/减弱通道两端的电压强度， 或增加/减弱渗透压， 另一种方式则是增加/减弱
: 通道的电导率， 即通过控制通道的电导率来实现信号的传输或抑制。
: 不知道， 在实际的神经系统中， 哪一种方式是在起主导作用？
: 有否相关的资料？ 望此领域的大侠不吝赐教。
: 多谢。


--
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