细胞的基本功能3-2008.pptVIP

Stimulus #1 Stimulus #2 (stronger) Time (milliseconds) Note the changes in threshold potential and AP amplitude Non-refractory period Relative Refractory Period (RRP) Absolute Refractory Period (ARP) Action Potential (AP) Threshold Threshold Membrane Potential (mV) Axon hillock Short Time Constant Time Long Time Constant Threshold Time Membrane potential at axon hillock (mV) Membrane potential at axon hillock (mV) Axon hillock Time ? Single excitatory postsynaptic potential Threshold Membrane potential at axon hillock (mV) Axon hillock Time ? Single excitatory postsynaptic potential Threshold Membrane potential at axon hillock (mV) Axon hillock Time ? Simultaneous excitatory postsynaptic potential Threshold Membrane potential at axon hillock (mV) A B C D E Sink Source Propagation Propagation Nodes of Ranvier t1 t2 t3 t4 Sink Source Sink Source Sink Source Sink Source Sink Source Sink Source Sink Source Sink Source UNMYELINATED AXON Action potential generated at each succeeding adjacent membrane segment MYELINATED AXON Saltatory conduction action potential jumps from node to node Ion Cytoplasm (mmol/L) Extracellular fluid (mmol/L) Nernst potential (mV) K+ 400 20 -75 Na+ 50 440 +55 Cl- 52 560 -60 A- 385 - - Distribution of the Major Ions Across the Membrane of the Squid Giant Axon 膜对K+通透 膜对Na+通透 组织的兴奋和兴奋性 兴奋性 Excitability 刺激(stimulus) → 反应(reaction) 动作电位 (action potential) 兴奋 Excitation excitation → action potential 产生action potential 的过程 可兴奋组织 Excitable tissue: Nerves, Gland, Muscle Excitability and factors for stimulus inducing excitation 兴奋产生的条件 刺激强度(intensity) 刺激的持续时间(duration) 强度对时间的变化率(intensity-duration) 阈强度 阈值(threshold) ** 组织的excitability 与 threshold 呈反比 为衡量组织兴奋性 高低的标准 组织excitable及其恢复过程中excitability的变化 绝对不应期(absolute refractory period): 兴奋性为零 相对不应期(relative refractory period): 阈上刺激产生反应 超常期