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Goldman–Hodgkin–Katz flux equation

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where subscripts 'i' and 'o' denote the intra- and extracellular compartments, respectively. Intuitively one may understand these limits as follows: if an ion is only found outside a cell, then the flux is Ohmic (proportional to voltage) when the voltage causes the ion to flow into the cell, but no
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Since one of the assumptions of the GHK flux equation is that the ions move independently of each other, the total flow of ions across the membrane is simply equal to the sum of two oppositely directed fluxes. Each flux approaches an
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scaled by the surface area). As the ratio between the two concentrations increases, so does the difference between the two slopes, meaning that the current is larger in one direction than the other, given an equal
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and the concentrations of the ion inside and outside of the cell. Since both the voltage and the concentration gradients influence the movement of ions, this process is a simplified version of
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of opposite signs. This is contrary to the result obtained if using Ohm's law scaled by the surface area, and the effect is called
2341: 2106: 1013:{\displaystyle \lim _{V_{m}\rightarrow 0}\Phi _{S}=P_{S}{\frac {z_{S}^{2}F^{2}}{RT}}{\frac {_{i}-_{o}\exp(-z_{S}V_{m}F/RT))]'}{'}}} 362:{\displaystyle \Phi _{S}=P_{S}z_{S}^{2}{\frac {V_{m}F^{2}}{RT}}{\frac {_{i}-_{o}\exp(-z_{S}V_{m}F/RT)}{1-\exp(-z_{S}V_{m}F/RT)}}} 1329: 555: 499: 493:
is shown to be contained in the GHK flux equation (Flax 2008). The proof is replicated from the reference (Flax 2008) here.
2597: 1689: 62: 2459:. It is evident that the ratio between the two asymptotes is merely the ratio between the two concentrations of S, 2417:
voltage could cause the ion to flow out of the cell, since there are no ions inside the cell in the first place.
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We wish to show that when the flux is zero, the transmembrane potential is not zero. Formally it is written
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and the GHK flux equation is a solution to the Nernst–Planck equation with the assumptions listed below.
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The electrical field is constant so that the transmembrane potential varies linearly across the membrane
2330:{\displaystyle \Phi _{S|o\to i}=P_{S}z_{S}^{2}{\frac {V_{m}F^{2}}{RT}}_{o}\ {\mbox{for}}\ V_{m}\ll \;0} 2095:{\displaystyle \Phi _{S|i\to o}=P_{S}z_{S}^{2}{\frac {V_{m}F^{2}}{RT}}_{i}\ {\mbox{for}}\ V_{m}\gg \;0} 1254: 1221: 461: 687: 2592: 78: 2572: 1391: 712: 490: 82: 54: 97:
Several assumptions are made in deriving the GHK flux equation (Hille 2001, p. 445) :
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Goldman-Hodgkin-Katz Cochlear Hair Cell Models – a Foundation for Nonlinear Cochlear Mechanics
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is the current density (flux) outward through the membrane carried by ion S, measured in
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The ions access the membrane instantaneously from the intra- and extracellular solutions
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is large and/or when one or both of the concentrations change considerably during an
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The movement of ions is affected by both concentration and voltage differences
2477: 1943: 45:(or GHK flux equation or GHK current density equation) describes the ionic 1175:{\displaystyle \lim _{V_{m}\rightarrow 0}\Phi _{S}=P_{S}z_{S}F(_{i}-_{o})} 474:
is the intracellular concentration of ion S, measured in mol·m or mmol·l
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as the membrane potential diverges from zero. These asymptotes are
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is the extracellular concentration of ion S, measured in mol·m
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The GHK flux equation for an ion S (Hille 2001, p. 445):
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is the permeability of the membrane for ion S measured in m·s
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constant, the equation yields a straight line when plotting
2535:, 3rd ed., Sinauer Associates, Sunderland, Massachusetts. 1054:
represents the differential of f and the result is :
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cycle can change 100-fold or more, and the ratio between
1375:{\displaystyle \lim _{\Phi _{S}\rightarrow 0}V_{m}\neq 0} 601:{\displaystyle \lim _{V_{m}\rightarrow 0}\Phi _{S}\neq 0} 545:{\displaystyle \lim _{\Phi _{S}\rightarrow 0}V_{m}\neq 0} 611:
However, due to the form of the GHK flux equation when
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Expression of the ionic flux across a cell membrane
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This is a problem as the value of 2533:Ion channels of excitable membranes 2435: 2346: 2192: 2111: 1957: 1432: 1396: 1339: 1226: 1088: 756: 652: 583: 509: 444:, equal to 96,485 C·mol or J·V·mol 431:is the transmembrane potential in 383: 133: 81:, and the English Nobel laureates 43:Goldman–Hodgkin–Katz flux equation 25: 1316:{\displaystyle (_{i}-_{o})\neq 0} 110:The permeant ions do not interact 1244:{\displaystyle \Phi _{S}\neq 0} 552:which is equivalent to writing 2361: 2354: 2288: 2277: 2207: 2200: 2126: 2119: 2053: 2042: 1972: 1965: 1907: 1896: 1885: 1874: 1782: 1742: 1727: 1716: 1704: 1693: 1664: 1624: 1607: 1604: 1564: 1549: 1538: 1526: 1515: 1512: 1348: 1304: 1295: 1284: 1272: 1261: 1258: 1169: 1160: 1149: 1137: 1126: 1123: 1079: 1037: 1030: 1000: 996: 956: 941: 932: 928: 925: 885: 870: 859: 847: 836: 833: 820: 747: 704:{\displaystyle {\frac {0}{0}}} 574: 518: 353: 313: 296: 256: 241: 230: 218: 207: 1: 2548:and Holmes, W.Harvey (2008). 468:(= degrees Celsius + 273.15) 1414:{\displaystyle \Phi _{S}=0} 2614: 2519:can reach 20,000 or more. 29: 2588:Electrochemical equations 2420:Keeping all terms except 2509:cardiac action potential 1683:which reduces to : 454:, equal to 8.314 J·K·mol 30:Not to be confused with 2487:when the ratio between 1211:{\displaystyle V_{m}=0} 637:{\displaystyle V_{m}=0} 422:is the valence of ion S 89:derived this equation. 55:transmembrane potential 2442: 2407: 2331: 2172: 2096: 1927: 1795: 1674: 1415: 1376: 1317: 1245: 1212: 1176: 1048: 1014: 705: 678: 638: 602: 546: 404:per square meter (A·m) 390: 363: 63:Nernst–Planck equation 2443: 2441:{\displaystyle \Phi } 2408: 2332: 2173: 2097: 1928: 1796: 1675: 1416: 1377: 1318: 1246: 1213: 1177: 1049: 1015: 706: 679: 639: 603: 547: 391: 389:{\displaystyle \Phi } 364: 53:as a function of the 2485:electrophysiologists 2432: 2342: 2188: 2107: 1953: 1815: 1690: 1428: 1392: 1330: 1255: 1222: 1189: 1061: 1027: 729: 688: 648: 615: 556: 500: 462:absolute temperature 380: 129: 2598:Bioelectrochemistry 2242: 2007: 1477: 795: 169: 79:Columbia University 2573:Reversal potential 2438: 2403: 2381: 2327: 2305: 2285: 2228: 2168: 2146: 2092: 2070: 2050: 1993: 1923: 1904: 1882: 1791: 1724: 1701: 1670: 1546: 1523: 1463: 1411: 1372: 1355: 1313: 1292: 1269: 1241: 1208: 1172: 1157: 1134: 1086: 1044: 1010: 867: 844: 781: 754: 701: 674: 634: 598: 581: 542: 525: 491:reversal potential 386: 359: 238: 215: 155: 83:Alan Lloyd Hodgkin 2541:978-0-87893-321-1 2507:, which during a 2385: 2380: 2309: 2304: 2299: 2284: 2275: 2150: 2145: 2074: 2069: 2064: 2049: 2040: 1917: 1903: 1881: 1859: 1804:and produces the 1723: 1700: 1668: 1545: 1522: 1497: 1333: 1291: 1268: 1156: 1133: 1064: 1047:{\displaystyle '} 1008: 866: 843: 815: 732: 699: 672: 559: 503: 357: 237: 214: 202: 18:GHK flux equation 16:(Redirected from 2605: 2563:Goldman equation 2497:action potential 2447: 2445: 2444: 2439: 2412: 2410: 2409: 2404: 2395: 2394: 2383: 2382: 2378: 2368: 2367: 2357: 2336: 2334: 2333: 2328: 2319: 2318: 2307: 2306: 2302: 2297: 2296: 2295: 2286: 2282: 2276: 2274: 2266: 2265: 2264: 2255: 2254: 2244: 2241: 2236: 2227: 2226: 2214: 2213: 2203: 2177: 2175: 2174: 2169: 2160: 2159: 2148: 2147: 2143: 2133: 2132: 2122: 2101: 2099: 2098: 2093: 2084: 2083: 2072: 2071: 2067: 2062: 2061: 2060: 2051: 2047: 2041: 2039: 2031: 2030: 2029: 2020: 2019: 2009: 2006: 2001: 1992: 1991: 1979: 1978: 1968: 1944:asymptotic value 1932: 1930: 1929: 1924: 1922: 1918: 1916: 1915: 1914: 1905: 1901: 1894: 1893: 1892: 1883: 1879: 1872: 1860: 1858: 1854: 1853: 1843: 1835: 1827: 1826: 1800: 1798: 1797: 1792: 1775: 1767: 1766: 1757: 1756: 1735: 1734: 1725: 1721: 1712: 1711: 1702: 1698: 1679: 1677: 1676: 1671: 1669: 1667: 1657: 1649: 1648: 1639: 1638: 1610: 1597: 1589: 1588: 1579: 1578: 1557: 1556: 1547: 1543: 1534: 1533: 1524: 1520: 1511: 1510: 1500: 1498: 1496: 1488: 1487: 1486: 1476: 1471: 1461: 1459: 1458: 1440: 1439: 1420: 1418: 1417: 1412: 1404: 1403: 1381: 1379: 1378: 1373: 1365: 1364: 1354: 1347: 1346: 1322: 1320: 1319: 1314: 1303: 1302: 1293: 1289: 1280: 1279: 1270: 1266: 1250: 1248: 1247: 1242: 1234: 1233: 1217: 1215: 1214: 1209: 1201: 1200: 1181: 1179: 1178: 1173: 1168: 1167: 1158: 1154: 1145: 1144: 1135: 1131: 1119: 1118: 1109: 1108: 1096: 1095: 1085: 1078: 1077: 1053: 1051: 1050: 1045: 1043: 1019: 1017: 1016: 1011: 1009: 1007: 1006: 989: 981: 980: 971: 970: 939: 938: 918: 910: 909: 900: 899: 878: 877: 868: 864: 855: 854: 845: 841: 832: 831: 818: 816: 814: 806: 805: 804: 794: 789: 779: 777: 776: 764: 763: 753: 746: 745: 720:l'Hôpital's rule 710: 708: 707: 702: 700: 692: 683: 681: 680: 675: 673: 665: 660: 659: 643: 641: 640: 635: 627: 626: 607: 605: 604: 599: 591: 590: 580: 573: 572: 551: 549: 548: 543: 535: 534: 524: 517: 516: 442:Faraday constant 395: 393: 392: 387: 368: 366: 365: 360: 358: 356: 346: 338: 337: 328: 327: 299: 289: 281: 280: 271: 270: 249: 248: 239: 235: 226: 225: 216: 212: 205: 203: 201: 193: 192: 191: 182: 181: 171: 168: 163: 154: 153: 141: 140: 75:David E. Goldman 59:electrodiffusion 32:Goldman equation 21: 2613: 2612: 2608: 2607: 2606: 2604: 2603: 2602: 2578: 2577: 2568:Nernst equation 2559: 2525: 2518: 2514: 2506: 2494: 2490: 2466: 2462: 2458: 2451: 2430: 2429: 2426: 2386: 2345: 2340: 2339: 2310: 2287: 2267: 2256: 2246: 2245: 2218: 2191: 2186: 2185: 2151: 2110: 2105: 2104: 2075: 2052: 2032: 2021: 2011: 2010: 1983: 1956: 1951: 1950: 1939: 1906: 1895: 1884: 1873: 1867: 1845: 1844: 1836: 1818: 1813: 1812: 1806:Nernst equation 1758: 1748: 1726: 1703: 1688: 1687: 1640: 1630: 1611: 1580: 1570: 1548: 1525: 1502: 1501: 1489: 1478: 1462: 1450: 1431: 1426: 1425: 1395: 1390: 1389: 1356: 1338: 1328: 1327: 1294: 1271: 1253: 1252: 1225: 1220: 1219: 1192: 1187: 1186: 1159: 1136: 1110: 1100: 1087: 1069: 1059: 1058: 1036: 1025: 1024: 999: 972: 962: 940: 931: 901: 891: 869: 846: 823: 819: 807: 796: 780: 768: 755: 737: 727: 726: 686: 685: 651: 646: 645: 618: 613: 612: 582: 564: 554: 553: 526: 508: 498: 497: 487: 479: 473: 430: 421: 412: 399: 378: 377: 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1343: 1326: 1325: 1324: 1310: 1307: 1299: 1281: 1276: 1238: 1235: 1230: 1205: 1202: 1197: 1193: 1164: 1146: 1141: 1120: 1115: 1111: 1105: 1101: 1097: 1092: 1082: 1074: 1070: 1057: 1056: 1055: 1040: 1033: 1003: 993: 990: 986: 982: 977: 973: 967: 963: 959: 953: 950: 947: 944: 935: 922: 919: 915: 911: 906: 902: 896: 892: 888: 882: 879: 874: 856: 851: 828: 824: 811: 808: 801: 797: 791: 786: 782: 773: 769: 765: 760: 750: 742: 738: 725: 724: 723: 721: 716: 714: 713:indeterminate 696: 693: 669: 666: 661: 656: 631: 628: 623: 619: 609: 595: 592: 587: 577: 569: 565: 539: 536: 531: 527: 521: 513: 494: 492: 484: 476: 470: 467: 463: 459: 456: 453: 449: 446: 443: 439: 436: 434: 427: 424: 418: 415: 409: 406: 403: 396: 375: 374: 373: 350: 347: 343: 339: 334: 330: 324: 320: 316: 310: 307: 304: 301: 293: 290: 286: 282: 277: 273: 267: 263: 259: 253: 250: 245: 227: 222: 198: 195: 188: 184: 178: 174: 165: 160: 156: 150: 146: 142: 137: 125: 124: 123: 117: 112: 109: 106: 103: 100: 99: 98: 92: 90: 88: 84: 80: 76: 73:The American 68: 66: 64: 60: 56: 52: 51:cell membrane 48: 44: 37: 33: 19: 2549: 2532: 2482: 2453: 2428: 2421: 2419: 2415: 2180: 1940: 1803: 1682: 1387: 1384: 1184: 1022: 717: 610: 495: 488: 457: 452:gas constant 447: 437: 425: 416: 407: 376: 371: 121: 96: 87:Bernard Katz 72: 58: 42: 40: 1388:By setting 718:We turn to 93:Assumptions 2593:Biophysics 2582:Categories 2523:References 1323:and thus 2469:Ohm's law 2436:Φ 2397:≫ 2362:→ 2347:Φ 2321:≪ 2208:→ 2193:Φ 2162:≪ 2127:→ 2112:Φ 2086:≫ 1973:→ 1958:Φ 1865:⁡ 1832:− 1746:− 1740:⁡ 1714:− 1628:− 1622:⁡ 1616:− 1568:− 1562:⁡ 1536:− 1433:Φ 1397:Φ 1367:≠ 1349:→ 1340:Φ 1308:≠ 1282:− 1236:≠ 1227:Φ 1147:− 1089:Φ 1080:→ 960:− 954:⁡ 948:− 889:− 883:⁡ 857:− 757:Φ 748:→ 653:Φ 593:≠ 584:Φ 575:→ 537:≠ 519:→ 510:Φ 384:Φ 317:− 311:⁡ 305:− 260:− 254:⁡ 228:− 134:Φ 49:across a 2557:See also 2531:(2001). 2452:against 1808: : 1041:′ 1004:′ 936:′ 118:Equation 2501:calcium 466:kelvins 460:is the 450:is the 440:is the 402:amperes 2539:  2384:  2308:  2298:  2149:  2073:  2063:  1023:where 372:where 69:Origin 433:volts 2537:ISBN 2515:and 2491:and 2463:and 2181:and 489:The 85:and 47:flux 41:The 2379:for 2303:for 2144:for 2068:for 1737:exp 1619:exp 1559:exp 1335:lim 1251:if 1066:lim 951:exp 880:exp 734:lim 711:is 561:lim 505:lim 308:exp 251:exp 77:of 34:or 2584:: 2503:, 2480:. 1862:ln 1218:, 715:. 644:, 2517:i 2513:o 2505:i 2493:o 2489:i 2465:o 2461:i 2457:m 2454:V 2450:S 2425:m 2422:V 2401:0 2392:m 2388:V 2373:0 2370:= 2365:i 2359:o 2355:| 2351:S 2325:0 2316:m 2312:V 2293:o 2289:] 2283:S 2278:[ 2272:T 2269:R 2262:2 2258:F 2252:m 2248:V 2239:2 2234:S 2230:z 2224:S 2220:P 2216:= 2211:i 2205:o 2201:| 2197:S 2166:0 2157:m 2153:V 2138:0 2135:= 2130:o 2124:i 2120:| 2116:S 2090:0 2081:m 2077:V 2058:i 2054:] 2048:S 2043:[ 2037:T 2034:R 2027:2 2023:F 2017:m 2013:V 2004:2 1999:S 1995:z 1989:S 1985:P 1981:= 1976:o 1970:i 1966:| 1962:S 1920:) 1912:o 1908:] 1902:S 1897:[ 1890:i 1886:] 1880:S 1875:[ 1869:( 1856:F 1851:S 1847:z 1841:T 1838:R 1829:= 1824:m 1820:V 1789:0 1786:= 1783:) 1780:T 1777:R 1773:/ 1769:F 1764:m 1760:V 1754:S 1750:z 1743:( 1732:o 1728:] 1722:S 1717:[ 1709:i 1705:] 1699:S 1694:[ 1665:) 1662:T 1659:R 1655:/ 1651:F 1646:m 1642:V 1636:S 1632:z 1625:( 1613:1 1608:) 1605:) 1602:T 1599:R 1595:/ 1591:F 1586:m 1582:V 1576:S 1572:z 1565:( 1554:o 1550:] 1544:S 1539:[ 1531:i 1527:] 1521:S 1516:[ 1513:( 1508:m 1504:V 1494:T 1491:R 1484:2 1480:F 1474:2 1469:S 1465:z 1456:S 1452:P 1448:= 1445:0 1442:= 1437:S 1409:0 1406:= 1401:S 1370:0 1362:m 1358:V 1352:0 1344:S 1311:0 1305:) 1300:o 1296:] 1290:S 1285:[ 1277:i 1273:] 1267:S 1262:[ 1259:( 1239:0 1231:S 1206:0 1203:= 1198:m 1194:V 1170:) 1165:o 1161:] 1155:S 1150:[ 1142:i 1138:] 1132:S 1127:[ 1124:( 1121:F 1116:S 1112:z 1106:S 1102:P 1098:= 1093:S 1083:0 1075:m 1071:V 1038:] 1034:f 1031:[ 1001:] 997:) 994:T 991:R 987:/ 983:F 978:m 974:V 968:S 964:z 957:( 945:1 942:[ 933:] 929:) 926:) 923:T 920:R 916:/ 912:F 907:m 903:V 897:S 893:z 886:( 875:o 871:] 865:S 860:[ 852:i 848:] 842:S 837:[ 834:( 829:m 825:V 821:[ 812:T 809:R 802:2 798:F 792:2 787:S 783:z 774:S 770:P 766:= 761:S 751:0 743:m 739:V 697:0 694:0 670:0 667:0 662:= 657:S 632:0 629:= 624:m 620:V 596:0 588:S 578:0 570:m 566:V 540:0 532:m 528:V 522:0 514:S 478:o 472:i 458:T 448:R 438:F 429:m 426:V 420:S 417:z 411:S 408:P 398:S 354:) 351:T 348:R 344:/ 340:F 335:m 331:V 325:S 321:z 314:( 302:1 297:) 294:T 291:R 287:/ 283:F 278:m 274:V 268:S 264:z 257:( 246:o 242:] 236:S 231:[ 223:i 219:] 213:S 208:[ 199:T 196:R 189:2 185:F 179:m 175:V 166:2 161:S 157:z 151:S 147:P 143:= 138:S 38:. 20:)

Index

GHK flux equation
Goldman equation
Goldman–Hodgkin–Katz voltage equation
flux
cell membrane
transmembrane potential
Nernst–Planck equation
David E. Goldman
Columbia University
Alan Lloyd Hodgkin
Bernard Katz
amperes
volts
Faraday constant
gas constant
absolute temperature
kelvins
reversal potential
indeterminate
l'Hôpital's rule
Nernst equation
asymptotic value
Ohm's law
driving force
rectification
electrophysiologists
action potential
calcium
cardiac action potential
Hille, Bertil

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