神经生物学 神经元及其静息态的膜特性.ppt

跨膜通道蛋白 离子通道 离子泵 离子运动: 扩散（diffusion） 浓度梯度造成离子扩散 扩散=扩散系数x浓度梯度 离子运动: 电迁移（electrical drift） 遵从欧姆定律 电流=电位x电导 静息膜电位（resting membrane potential） 离子平衡电位（equilibrium potential） 扩散与电迁移达到平衡-电化学平衡 离子平衡态的特征 膜电位的产生由极少离子运动造成 离子电荷的差异集中在膜的两侧 离子运动驱动力=膜电位-离子平衡电位 平衡电位可由膜两侧的离子浓度计算：能斯特方程 能斯特方程（Nernst equation） T: 绝对温度 (K) R: 气体常数 (8.31 joule/K-mol) F: 法拉第常熟 (96480 C/mol) z: 离子电荷 (dimensionless) V: 电位(V) [C]: 离子浓度 (molecules/cm3 关键离子在神经元胞内合胞外的分布 离子梯度的维持 离子的主动运输 A Na/K-ATPase pump Ca-ATPase pump Na-Ca cotransporter K-Cl cotransporter B C D 生电泵（Electrogenic pumps） 如果膜在静息状态下仅对K通透，则静息膜电位=K平衡电位，事实如此吗？ 1 10 0 -10 -20 -30 -40 -50 -60 -70 1 10 100 [K+]out (mM) PK only Goldman-Hodgkin-Katz (GHK) 方程 10 100 [K+]out (mM) PK : Pna : PCl = 1 : 0.03 : 0.1 离子的相对通透率： 膜的等效电路 Im IC Ii I-V curve 膜的平行电导模型 离子电导与开放的离子通道数目成正比 离子电流=电位差x离子电导 神经元的电紧张特性 电紧张特性（Electrotonic properties）: 电信号在神经元胞体和神经突起中的被动传递 球形神经元：等电位 (isopotential) I0 Im 输入阻抗: 电缆状：非等电 (nonisopotential) 神经元的电紧张特性 树突电缆上去极化的衰减是距离的函数 In 1783, according to popular version of the story, Galvani dissected a frog at a table where he had been conducting experiments with static electricity. Galvanis assistant touched an exposed sciatic nerve of the frog with a metal scalpel, which had picked up a charge. At that moment, they saw sparks and the dead frogs leg kick as if in life. The observation made Galvani the first investigator to appreciate the relationship between electricity and animation — or life. This finding provided the basis for the current understanding that electrical energy (carried by ions), and not air or fluid as in earlier balloonist theories, is the impetus behind muscle movement. He is poorly credited with the discovery of bioelectricity. Galvani called the term animal electricity to describe whatever it was that activated the muscles of his specimens. Along with contemporaries, he regarded their activation as being generated by an electrical fluid that is carried to the muscles by the nerves. The phenomenon was dubbed galvanism, afte