IMED1001 Study Guide - Final Guide: Voltage-Gated Potassium Channel, Electrochemical Gradient, Depolarization
Document Summary
Open when bound by a specific ligand (chemical messenger) Open when membrane potential voltage exceeds threshold (-55 mv) Inactivated for a few ms afterwards. Voltage-gated channels k+ (k ) channels v. Open due to membrane potential voltage exceeding threshold. Slower to open than nav channels (open later) Sub-threshold stimuli cause some na+ channels to open. Some na+ enters cell in turn causing further depolarisation. Once threshold membrane potential is exceeded, all voltage-gated na+ channels open. Na+ floods into cell down its electrochemical gradient, causing rapid rise in membrane potential. At peak mp, the cell is highly positively charged compared to ecf. Once cell mp peaks, voltage- gated na+ channels close & voltage gated k+ channels open. K+ floods out of cell down electrochemical gradient causing repolarisation. After repolarisation, low k+ in cell & na+ is being pumped out. K+ channels are slower to close, so k+ leaks back into cell. Causes icf to be more negative than at rest.
