离子通道和神经元的电活动.ppt

Neuronal Electric Activities 神经元的电活动,主讲教师 刘风雨 万有 神经科学研究所、神经生物学系,Neuronal Electric Activities Include:,Rest Potential (Chapter 3) Action Potential (Chapter 4) Local Potentials Post-Synaptic Potential Excitatory Post-Synaptic Potential Inhibitory Post-Synaptic Potential End-plate Potential Receptor Potential,Chapter 3 The Neuronal Membrane at Rest,The CAST OF CHEMICALS Cytosol and Extracellular Fluid The Phospholipid Membrane Protein The MOVEMENT OF IONS Diffusion Electricity The IONIC BASIS OF RESTING MEMBRANE POTENTIAL Equilibrium Potential The Distribution of Ions Across the Membrane Relative Ion Permeabilities of Membrane at Rest The Importance of Regulating the External Potassium Concentration CONCLUDING REMARKS,Cytosol and Extracellular Fluid,Water: Its uneven distribution of electrical charge, so H2O is a polar molecule Ions: Salt dissolves readily in water because the charged portions of the water molecule have a stronger attraction for the ions than they have for each other,The Phospholipid Membrane (磷脂膜),The lipids of the neuronal membrane forming: a barrier to water-soluble ions a barrier to water,头端-极性磷酸盐-亲水,尾端-非极性碳氢化合物 -疏水,5,Protein,These proteins provide routes for ions to cross the neuronal membrane. The resting and action potentials depend on special proteins that span the phospholipid bilayer.,Protein – Amino Acids,The Peptide Bond (肽键) and a Polypeptide (多肽),Figure 3.6 Protein Structure,The primary structure,The secondary structure,The tertiary structure,The quaternary structure,Each of the different polypeptides contributing to a protein with quaternary structure is called a subunit (亚基).,Channel Proteins,Channel protein is suspended in a phospholipid bilayer, with its hydrophobic (疏水的) portion inside the membrane hydrophilic (亲水的) ends exposed to the watery environments on either side,Figure 3.7 A Membrane Ion Channel,10,Two Properties of Ion Channels,Ion selectivity (离子选择性) The diameter of the pore The nature of the R groups lining it Gating (门控特性) Channels with this property can be opened and closed-gated by changes in the local microenvironment of the membrane,Ion Pumps (离子泵),Ion pumps are enzymes that use the energy released by the breakdown of ATP to transport certain ions across the membrane,Chapter 3 The Neuronal Membrane at Rest,THE CAST OF CHEMICALS Cytosol and Extracellular Fluid The Phospholipid Membrane Protein THE MOVEMENT OF IONS Diffusion Electricity THE IONIC BASIS OF RESTING MEMBRANE POTENTIAL Equilibrium Potential The Distribution of Ions Across the Membrane Relative Ion Permeabilities of Membrane at Rest The Importance of Regulating the External Potassium Concentration CONCLUDING REMARKS,THE MOVEMENT OF IONS,A channel across a membrane is like a bridge across a river. An open channel  A net movement of ions across the membrane. Ion movement requires that external forces be applied to drive ions across. Two factors influence ion movement through channels: Diffusion (扩散) Electricity (电势差),Diffusion,Temperature-dependent random movement of ions and molecules tends to distribute the ions evenly throughout the solution so that there is a net movement of ions from regions of high concentration to regions of low concentration. This movement is called diffusion (扩散). A difference in concentration is called a concentration gradient (浓度梯度).,15,Figure 3.8 Diffusion,Driving ions across the membrane by diffusion happens when The membrane possesses channels permeable to the ions There is a concentration gradient across the membrane,Electricity,Another way to induce a net movement of ions in a solution is to use an electrical field (电场), because ions are electrically charged particles. Opposite charges attract and like charges repel.,Figure 3.9 The movement of ions influenced by an electrical field,,Opposite charges attract and like charges repel,Electricity,Two important factors determine how much current (I) will flow: Electrical potential (V, 电势) Electrical conductance (g, 电导) Electrical conductance Electrical resistance (电阻, R=1/g) Ohm’s law: I = gV,Figure 3.10 Electrical current flow across a membrane,Driving an ion across the membrane electrically requires The membrane possesses channels permeable to the ions There is a electrical potential difference across the membrane,20,Diffusion and Electricity,Electrical charged ions in solution on either side of the neuronal membrane. (带电离子溶解在细胞膜两侧的溶液中) Ions can cross the membrane only by protein channel. (离子必须通过离子通道实现跨膜运动) The protein channels can be highly selective for specific ions. (离子通道对离子具有高度的选择性) The movement of any ion through channel depends on the concentration gradient and the difference in electrical potential across the membrane. (离子的跨膜运动依赖于膜两侧的浓度梯度和电位差),Chapter 3 The Neuronal Membrane at Rest,The CAST OF CHEMICALS Cytosol and Extracellular Fluid The Phospholipid Membrane Protein The MOVEMENT OF IONS Diffusion Electricity The IONIC BASIS OF RESTING MEMBRANE POTENTIAL Equilibrium Potential The Distribution of Ions Across the 。