* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download BOX 5.2 GOLDMAN-HODGKIN-KATZ EQUATION An equation
Survey
Document related concepts
Synaptic gating wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Signal transduction wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Node of Ranvier wikipedia , lookup
Synaptogenesis wikipedia , lookup
Nervous system network models wikipedia , lookup
SNARE (protein) wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Biological neuron model wikipedia , lookup
Single-unit recording wikipedia , lookup
Stimulus (physiology) wikipedia , lookup
Action potential wikipedia , lookup
Patch clamp wikipedia , lookup
Electrophysiology wikipedia , lookup
End-plate potential wikipedia , lookup
Transcript
BOX 5.2 GOLDMAN-HODGKIN-KATZ EQUATION An equation developed by Goldman and later used by Alan Hodgkin and Bernard Katz describes the steady-state membrane potential for a given set of ionic concentrations inside and outside the cell and the relative permeabilities of the membrane to each of those ions: The relative contribution of each ion is determined by its concentration differences across the membrane and the relative permeability (pK, pNa, pCl) of the membrane to each type of ion. If a membrane is permeable to only one ion, then the Goldman–Hodgkin–Katz equation reduces to the Nernst equation. In the squid giant axon, at resting membrane potential, the permeability ratios are pK : pNa : pCl =1:00 : 0:04 : 0:45: The membrane of the squid giant axon, at rest, is most permeable to K+ ions, less so to Cl−, and least permeable to Na+. (Chloride appears to contribute considerably less to the determination of the resting potential of mammalian neurons.) These results indicate that the resting membrane potential is determined by the resting permeability of the membrane to K+, Na+, and Cl−. In theory, this resting membrane potential may be anywhere between EK (e.g., −76mV) and ENa (55mV). For the three ions at 20°C, the equation is This suggests that the squid giant axon should have a resting membrane potential of −62 mV. In fact, the resting membrane potential may be a few millivolts hyperpolarized to this value through the operation of the electrogenic Na+–K+ pump. David A. McCormick