exocytosi and endocytosis课件.ppt

Receptor-mediated endocytosis Nernst potential for the inside of membrane is +61mv(Na+): minute diffusion of sodium ions through the K+-Na+ leak channels. Cytoplasm Ion channels Giga-seal Glass microelectrode Suction 1 μm Patch clamp recording Cell Membrane 100 ms 4 pA Closed Open Single channel record III Local Response Definition: Local response is a small change in membrane potential caused by a subthreshold stimulus Role of the Local Potential Facilitate the cell. This means it increase excitability of the stimulated cell Cause the cell to excite once it is summed to reach the threshold potential (一) exocytosis and endocytosis Exocytosis Endocytosis: (1)Phagocytosis (2)pinocytosis: fluid-phase endocytosis, Receptor-mediated endocytosis Section 2 Membrane Potentials and Action Potentials Electrical potential exist across the membranes of essential all cells of the body. Some cells, such as neuron and muscle cells, are “excitable” – that is, capable of generation of electrochemical impulses at their membranes. In most cases, these impulses can be used to transmit signals along the membranes. (一) Resting potential，RP Basic Electrophysiological Terms Polarization: a state in which membrane is polarized at rest, negative inside and positive outside. Depolarization: It means the membrane potential becomes less negative than the resting potential (close to zero). Hyperpolarization: It means that the membrane potential is more negative than the resting level. Repolarization: It means restoration of normal polarization state of membrane. It is a process in which the membrane potential returns toward from depolarized level to the normal resting membrane value. Na+ (+50~+70mV) ion equilibrium potential K+ (-90~-100mV) Leakage of K+ and Na+ through the nerve membrane Nernst Equation EK=60 log —————(mV) [K+]o [K+]i Origin of the normal resting membrane potential. 1.Co