Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1...
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Transcript of Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1...
![Page 1: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/1.jpg)
Chapter 2
Electrical signals of nerve cells
![Page 2: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/2.jpg)
細胞內的電位記錄
玻璃電極,直徑小於 1 um
刺激電極
記錄電極
HyperpolarizationDepolarizationThreshold potential
![Page 3: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/3.jpg)
離子的流動如何造成電訊號 ?
1. Create different ionic concentrations across cell membrane2. Membranes are selectively permeable to ions
![Page 4: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/4.jpg)
Electrochemical equilibrium: electricity & concentration gradient
只對 K+ 通透的膜
濃度差十倍時 膜電位差為 58 的倍數
![Page 5: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/5.jpg)
單一離子平衡電位的計算方式
• Nernst equation: EX = RT/zF ln [X]2/[X1]
• = 58/z log [X]2/[X1]
• z is the electrical charge
• EK = 58 log 1/10
• = -58 mV
• side 2 is a reference compartment, defined as 0 potential
![Page 6: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/6.jpg)
問題
1. Side 1: [Na+] = 1 mM Side 2: [Na+] = 10 mM
2. Side 1: [Ca2+] = 1 mM Side 2: [Ca2+] = 10 mM
3. Side 1: [Cl-] = 10 mM Side 2: [Cl-] = 1 mM
4. Side 1: [K+] = 100 mM Side 2: [K+] = 1 mM
![Page 7: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/7.jpg)
答案
1. ENa = 58/1*log 10/1 = 58 mV
2. ECa = 58/2*log 10/1 = 29 mV
3. ECl = 58/-1*log 1/10 = 58 mV
4. EK = 58/1*log 1/100 = -116 mV
![Page 8: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/8.jpg)
膜電位對離子流動的方向及大小的影響 p42
• Connect a battery across the two sides to make side 1 more negative than side 2
• Side 1 = -58 mV, no net K+ ion flow
• Side 1 more negative than -58 mV, K+ ion will flow form side 2 to side 1
![Page 9: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/9.jpg)
Electrochemical equilibrium in a multi-ion environment1. Permeability p432. Goldman equation
![Page 10: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/10.jpg)
Intracellular recording replace cytoplasmlarge synapse
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The ionic basis of the resting membrane potential
若休息膜電位
對
K+的通透性最好,則改變細胞外
K+濃
度將影響膜電位
![Page 12: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/12.jpg)
The ionic basis of action potential
移除N
a+
同時影響了上升速度及強
度
![Page 13: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/13.jpg)
Squid giant axonFrog motor neuron
axon Cell bodyCell body
Inferior olive Purkinje
Action potential form and nomenclature
Hodgkin & Katz 尚無法證實 membrane 是如何改變其 permeability 以 generate action potential
![Page 14: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/14.jpg)
Chapter 3
Voltage-dependent membrane potential
![Page 15: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/15.jpg)
Ionic currents across nerve cell membrane
• How the increase in Na+ permeability occurs?
• Voltage clamp method: Kenneth Cole, 1940s
1.2.
3.
4.
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Alan Hodgkin & Andrew Huxley, 1940s當膜電位改變時,是否有離子進出細胞膜?
Capacitive current: voltage clamp 輸入的電流
![Page 17: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/17.jpg)
Squid neuron: ENa = 55 mV
![Page 18: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/18.jpg)
![Page 19: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/19.jpg)
To test whether the earlycurrent is Na+ or not
![Page 20: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/20.jpg)
Toxins that poison ion channels: tetrodotoxin Na+
tetraethylammonium ions K+
證明造成這兩種離子通透性改變的機制,
是互相獨立的。
![Page 21: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/21.jpg)
Toxins that poison ion channels
減緩 Na+ channels inactivation
降低 threshold
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Two voltage-dependent membrane conductances
• V = IR = I * 1/g = I/g
• Ix = gV = g (Vm-Ex)
• Conclusions:
• (1) both Na+ and K+ conductances are voltage-dependent Fig. 3.6
![Page 23: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/23.jpg)
(2) the Na+ and K+ conductances change over time
![Page 24: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/24.jpg)
Reconstruction of the action potential
Rate of depolarization falls:(1) electrochemical driving force of Na+ decreases(2) Na+ conductance inactivates(3) K+ conductance increase
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Until Na+ conductance inactivation
Restore the membrane potential to the resting levelby inactivate K+ channels
![Page 26: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/26.jpg)
Threshold: (1) the point at which the amount of heat supplied exogenously = the amount of heat that can be dissipated (2) Na+ inflow = K+ outflow
![Page 27: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/27.jpg)
Long-distance signaling by means of action potentials
Passive current flow: current leak neurons are poor conductors than a wire
![Page 28: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/28.jpg)
How do action potentials propagate along such a poor conductor?
(1) the amplitude of AP(2) the time delay of AP
Conduction velocity
![Page 29: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/29.jpg)
Two types of voltage-dependent channels
![Page 30: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/30.jpg)
Voltage-dependent channels close
Refractory period(1) the number of AP/ time(2) propagate back
AP propagation:(1) passive flow(2) active flow by voltage- dependent channels
![Page 31: Chapter 2 Electrical signals of nerve cells. 細胞內的電位記錄 玻璃電極,直徑 小於 1 um 刺激電極 記錄電極 Hyperpolarization Depolarization Threshold potential.](https://reader033.fdocument.pub/reader033/viewer/2022061609/551b5386550346d41a8b611a/html5/thumbnails/31.jpg)
Increased conduction velocity as a result of mylination
Improve passive flow, increase velocity:(1) increase diameter, decreases the internal resistance(2) increase insulation Mylination:
CNS oligodendrocytePNS Schwann cells
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