3.Bioelectrical phenomena of the cell Several basic concepts Excitability Excitable cells or tissues Stimulus excitation Threshold stimulus,intensity or threshold Relationship between Excitability threshold Bioelectrical phenomena of nerve muscle cells Resting potential (RP) Action potential (AP)
§ 3. Bioelectrical phenomena of the cell • Several basic concepts * Excitability * Excitable cells or tissues * Stimulus & excitation * Threshold stimulus, intensity or threshold * Relationship between Excitability & threshold • Bioelectrical phenomena of nerve & muscle cells * Resting potential (RP) * Action potential (AP)
Resting potential (RP) A constant potential difference at rest Between both sides of the membrane Negative inside relative to outside -70 mV (neuron),-90 mV (muscle) Action potential (AP) Occurs when a stimulus is applied A brief deflection (spike)of the baseline Depolarization repolarization phases All or none not attenuated propagation
* Resting potential (RP) A constant potential difference at rest Between both sides of the membrane Negative inside relative to outside −70 mV (neuron), −90 mV (muscle) * Action potential (AP) Occurs when a stimulus is applied A brief deflection (spike) of the baseline Depolarization & repolarization phases All or none & not attenuated propagation
锋电位 负后电位 电位变化 正后电位 十-------- Relationship 超常期 兴奋性 between excitation & 不应期（相对和绝对不应期厂低常期 时间（ms) AP
Relationship between excitation & AP
放大器 示波器 放大器 ++4+t +++名+++++ 示波器 胞 第雨 ++++++++++ +++++++++ (1)电极A与B均置于细胞外表面 (2)电极B插人细胞内，电极A置于细胞膜外表 面，细胞膜呈现外正内负的极化状态 图2-4证明静息电位存在的实验示意图 Measurement of resting potential (RP)
Measurement of resting potential (RP)