没有幻灯片标题复旦大学精品课程NoslidetitleFudanUniversityboutiquecourse.ppt
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1、chap. 2 The resting membrane potential,chap. 3 Action potential,第二章 细胞的兴奋,from Berne & Levy Principles of Physiology (4th ed) 2005,chap. 16 Electrical activity of the heart,chap. 17 Natural excitation of the heart,Observations of Membrane Potentials,4. ACTION PONTIELS,1. IONIC EQUILIBRIA,2. RESTING
2、MEMBRANE POTENTIALS,3. SUBTHRESHOLD RESPONSES,5. 心肌细胞和起搏细胞的动作电位,Observations of Membrane Potentials,Extracellular recording,Intracellular recording,Voltage clamp,macroscopical current,Patch clamp,single channel current,1. IONIC EQUILIBRIA,Electrochemical Equilibrium,When the force caused by the conc
3、entration difference and the force caused by the electrical potential difference are equal and opposite, no net movement of the ion occurs, and the ion is said to be in electrochemical equilibrium across the membrane.,When an ion is in electrochemical equilibrium, the electrochemical potential diffe
4、rence is called as equilibrium potential or Nernst potential.,The Nernst Equation,Where EX equilibrium potential of X+ R ideal gas constant T absolute temperature z charge number of the ion F Faradays number natural logarithm of concentration ration of X+ on the two sides of the membrane,At any memb
5、rane potential other than the Ex , there will be an electrochemical driving force for the movement of X+ across the membrane, which tend to pull the membrane potential toward its EX.,The greater the difference between the membrane potential and the EX will result in a greater driving force for net m
6、ovement of ions.,Movement can only happen if there are open channels!,Distribution of Ions Across Plasma Membranes of a human skeletal muscle cell,2. RESTING MEMBRANE POTENTIALS,The cytoplasm is usually electrically negative relative to the extracellular fluid. This electrical potential difference a
7、cross the plasma membrane in a resting cell is called the resting membrane potential.,The Chord Conductance Equation,where Em membrane potential Es equilibrium potentials of the ion s gs conductance of the membrane to the ion s. the more permeable, the greater the conductance.,The Na+,K+-ATPase cont
8、ributes directly to generation of the resting membrane potential.,All the ions that the membrane is permeable to contribute to the establishment of the potential of the membrane at rest.,细胞膜在静息状态下对K+的通透性一般大于其它离子(主要是IK1),因此大多数细胞的静息膜电位都是胞内为负。,3. SUBTHRESHOLD RESPONSES,The size (amplitude) of the subth
9、reshold potential is directly proportional to the strength of the triggering event.,A subthreshold potential can be either hyperpolarizing (make membrane potential more negative) or depolarizing (make membrane potential more positive),graded potential,This passive spread of electrical signals with n
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