神经生物学ppt课件:3离子通道和神经元的电活动.ppt
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Neuronal Electric Activities
神经元的电活动
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
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
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
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 regionsof low concentration. This movement is called diffusion (扩散).
? A difference in concentration is called a concentration gradient (浓度梯度).
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
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
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 Membrane
- Relative Ion Permeabilities of Membrane at Rest
- The Importance of Regulating the External Potassium Concentration
? CONCLUDING REMARKS
THE IONIC BASIS OF THE RESTING MEMBRANE POTENTIAL (静息电位)
? The membrane potential (膜电位) is the voltage across the neuronal membrane at any moment, represented by the symbol mV.
? Microelectrode
(微电极) and mV measurement
Establishing Equilibrium Potential (平衡电位)
Figure 3.12Establishing equilibrium in a selectively permeable membrane
Equilibrium potentials
? The electrical potential difference that exactly balances an ionic concentration gradient is called an ionic equilibrium potential, or simply equilibrium potential......（后略) ......
Neuronal Electric Activities
神经元的电活动
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
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
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
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 regionsof low concentration. This movement is called diffusion (扩散).
? A difference in concentration is called a concentration gradient (浓度梯度).
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
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
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 Membrane
- Relative Ion Permeabilities of Membrane at Rest
- The Importance of Regulating the External Potassium Concentration
? CONCLUDING REMARKS
THE IONIC BASIS OF THE RESTING MEMBRANE POTENTIAL (静息电位)
? The membrane potential (膜电位) is the voltage across the neuronal membrane at any moment, represented by the symbol mV.
? Microelectrode
(微电极) and mV measurement
Establishing Equilibrium Potential (平衡电位)
Figure 3.12Establishing equilibrium in a selectively permeable membrane
Equilibrium potentials
? The electrical potential difference that exactly balances an ionic concentration gradient is called an ionic equilibrium potential, or simply equilibrium potential......（后略) ......
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