Download presentation

Presentation is loading. Please wait.

Published byUnique Mallory Modified over 2 years ago

1
Communication between cells

2
R I1I1 Biology Electrical equivalent I2I2 I = I 1 + I 2 I

3
Nernst Equation The Nernst equation relates the potential difference to the concentration difference in equilibrium: C i / C o = exp { - Z e (V i -V o )/kT } or V i - V o = (kT/Ze) ln (C o /C i ) with e = charge electron Z = valence of ion k = Boltzmann constant T = temperature C i (C o ) = concentration inside (outside) membrane

4
Example of Nernst equation t=0 R + 50 N a + 50 Cl - 100 N a + 100 Cl - 100 t >> 0 R + 50 N a + 64 Cl - 114 N a + 86 Cl - 86 ΔV = 0ΔV = - 10 If both N a and Cl, but not R + can migrate through the membrane.

5
Nernst equation for squid axon

6
Problems with Nernst equation considers only a single ion. If multiple ions are involved, it assumes equal permeability for all ions Applies only to passive transport ions migrate independently of each other

7
Goldman/Hodgkin/Katz equation The Nernst equation relates the potential difference to the concentration difference in equilibrium for a single neuron. When several ions are involved, we obtain for equilibrium : P k [K] o +P Na [Na] o +P Cl [Cl] i ΔV = (RT/F) ln --------------------------------- P k [K] i +P Na [Na] i +P Cl [Cl] o with Pi = permeability of ion i [K] i/o = concentration inside/outside F = Faraday constant T = temperature ΔV = potential difference across membrane

8
Current through an ion channel

9
Schematic overview of the active membrane

10
Hodgkin & Huxley: Current through an ion-channel Ohm’s law Conductance G=1/R Conductance G is a product of maximal conductance g Ca and the fraction of open channels m 3 h R V ion outside inside 0 mV V mV I 0 mV V mV I

11
State: Gating kinetics

12
Open State: Gating kinetics

13
Open Closed mm mm m Probability: State: (1-m) mm mm Gating kinetics

14
V (mV) mm mm Open Closed mm mm m Probability: State: (1-m) mm mm Channel Open Probability: Gating kinetics

15
-150-100-50050100150 0 0.2 0.4 0.6 0.8 1 m (V) -150-100-50050100150 0 2 4 6 8 x 10 -3 m (V) m (s) -150-100-50050100150 0.2 0.4 0.6 0.8 1 1.2 h (V) V clamp (mV) -100-50050100 0 2 4 6 8 10 h (V) V clamp (mV) h (s) Parameter fitting (2)

16
-150-100-50050100150 0 0.2 0.4 0.6 0.8 1 m (V) -150-100-50050100150 0 2 4 6 8 x 10 -3 m (V) m (s) -150-100-50050100150 0.2 0.4 0.6 0.8 1 1.2 h (V) V clamp (mV) -100-50050100 0 2 4 6 8 10 h (V) V clamp (mV) h (s) Parameter fitting (2)

17
V (mV) mm mm Open Closed mm mm m Probability: State: (1-m) mm mm Channel Open Probability: Gating kinetics g m (t) = g m, max (m ∞ - m 0 )(1 - e -t/τ ) g h (t) = g h, max (h ∞ - h 0 )e -t/τ m3hm3h time g gmgm ghgh g Na

18
V mV 0 mV V mV 0 mV ICIC I Na Kirchoff’s law: Membrane voltage equation I Na = g max, Na m 3 h(V- V Na ) -C m dV/dt = g max, Na m 3 h(V-V na ) + g max, K n 4 (V-V K ) + g leak (V-V na )

19
Actionpotential

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on national education day images Ppt on 3g wireless networks Ppt on cement industry in india Ppt on special types of chromosomes mutation Genitourinary system anatomy and physiology ppt on cells Ppt on red ocean strategy with examples Ppt on accounting standard 12 Ppt on land resources and development Download ppt on pedal powered washing machine Ppt on conceptual art examples