E NEW YORK s 10己 Intracell chemical driving force K Na electrochemical Na balance Na Na++++++++十中+Mat electrical Na Na Na driving force Na Na Extracellular
chemical driving force electrical driving force ++++++++++++++++ - - - - - - - - - - - - - - - - - electrochemical balance
≡NEwY Equal 8 ②②②团团sdg oooOooOO Cytoplasmic Equal Source: Barrett KE, Barman SM, Boitano S, Brooks HL: Ganong'sReviewofMedicalpHysiologywww.accessmedicine.com Copyright (o The McGraw-Hill C s, Inc. All rights reserved A membrane potential results from separation of positive and negative charges across the cell membrane. The excess of positive charges (red circles) outside the cell and negative charges(blue circles) inside the cell at rest represents a small fraction of the total number of ions present
A membrane potential results from separation of positive and negative charges across the cell membrane. The excess of positive charges (red circles) outside the cell and negative charges (blue circles) inside the cell at rest represents a small fraction of the total number of ions present
E NEW YORK s raIn 10己 The Nernst Equation: rT lon o R=Gas constant e=relog T=Temperature Z=Valence K equilibr ZF lon 4 F=Faraday s constant (钾离子平衡电位) K o E=60o%(K+y
The Nernst Equation: K+ equilibrium potential (EK) (37oC) i o Ion Ion ZF RT E [ ] [ ] = log R=Gas constant T=Temperature Z=Valence F=Faraday’s constant ( ) [ ] [ ] 60log mV K K Ek i o + + = （钾离子平衡电位）
Begin Compartment 1 Compartment 2 0.15M 0.15M K+ in Compartment 2, Nat in Compartment 1 Nacl 工 KCI BUT only K+ can move K Na lon movement: K crosses into K Compartment 1 Nat Nat stays in Compartment 1.(d) K Nat At the potassium K equilibrium potential: Na buildup of positive charge in Compartment 1 produces an electrical potential that exactly offsets the K chemical concentration gradient
Begin: K+ in Compartment 2, Na+ in Compartment 1; BUT only K+ can move. Ion movement: K+ crosses into Compartment 1; Na+ stays in Compartment 1. buildup of positive charge in Compartment 1 produces an electrical potential that exactly offsets the K+ chemical concentration gradient. At the potassium equilibrium potential:
Begin: Compartment 1 Compartment 2 K in Compartment 2, 0.15M 0.15M Nat in Compartment 1; BUT only Nat can move. Nacl KCI lon movement Nat crosses into Na+一 Compartment 2: but K stays in K Compartment 2 Na Nat At the sodium K equilibrium potential buildup of positive charge in Compartment 2 produces an electrical potential that exactly offsets the Nat chemical concentration gradient
Begin: K+ in Compartment 2, Na+ in Compartment 1; BUT only Na+ can move. Ion movement: Na+ crosses into Compartment 2; but K+ stays in Compartment 2. buildup of positive charge in Compartment 2 produces an electrical potential that exactly offsets the Na+ chemical concentration gradient. At the sodium equilibrium potential: