Action potentials：动作电位28页PPT
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Diffusional forces acting on an ion
Given a mass of gas in thermal equilibrium we may measure its pressure (p) temperature (T) and volume (V). Boyle demonstrated that pV/T is a constant Volume occupied is proportional to the mass of gas, we can write the above constant as µR where µ is the mass in moles and R is a constant. R = 8.134 joule/mole K
15
16
17
Voltage clamp activated currents in axons
18
Na and K conductances that make the action potential
19
Current flowing across the giant axon membrane may be represented by the sum of conductive components (What we now identify as ion channels) and capacitance (the cell membrane). The currents are described in the following circuit diagram.
Equation #4
At a constant temperature this may be written as Equation #5
We can use this result to describe the free energy of diffusion of a particular ion in our cell or outside of the cell as follows:
Equation #8
(G)= (RTln(cout) +zFEout) —(RTln(cin) + zFEin)
Which simplifies to:
Equation #9)
(G) = R.T.ln(cout/cin) + z.F.δ(E)
By definition at equilibrium DG = 0 thus the equilibrium potential for any given ion is given by:
21
We may usefully consider the path of current flow to determine the effect of neurite geometry on electrical characteristics
22
Models for channel gating
-t/v
deltaVm(t) = Im.R(1-e )
20
When we consider the passive electrical environment of axons or dendrites it is useful to
think of them as composite structures
Gelect = zFE
8
The free energy of ions inside or outside of the cell is the sum of these forces
So the free energy (G) inside or outside of the cell may be expressed as
Equation #10 δ(E) = RT/ZF ln(cin/cout)
This is the Nernst-Einstein equation.
9
Current flowing across the giant axon membrane may be represented by the sum of conductive components (What we now identify as ion channels) and capacitance (the cell membrane). The currents are described in the following circuit diagram.
23
26
27
谢谢你的阅读
知识就是财富 丰富你的人生
Thus Equation #2
pV=µRT
Now the work done by an expanding gas can be calculated as foll expands from an initial volume Vi to a final volume Vf. Using equation #2, we can see that the work done per mole is
If z =valency of ion E = electrical potential across the delimiting membrane.
Thus the electrical energy in a mole of an ion may be expressed as
Equation #1
Equation #6
Gdiff = RTln(c)
7
Electrical forces acting on an ion
According to Faraday the charge on a mole of material is 96483 z Coulombs where z is the charge of each atom or ion (the valency of an ion). This is the Faraday constant or F.
Equation #7 G = Gdiff + Gelect = RTln(c) + zFE
(from #1 and #2)
The difference between free energy inside the cell and outside defines the free energy driving movement of the ion across the cell membrane which may be expressed as follows:
Given a mass of gas in thermal equilibrium we may measure its pressure (p) temperature (T) and volume (V). Boyle demonstrated that pV/T is a constant Volume occupied is proportional to the mass of gas, we can write the above constant as µR where µ is the mass in moles and R is a constant. R = 8.134 joule/mole K
15
16
17
Voltage clamp activated currents in axons
18
Na and K conductances that make the action potential
19
Current flowing across the giant axon membrane may be represented by the sum of conductive components (What we now identify as ion channels) and capacitance (the cell membrane). The currents are described in the following circuit diagram.
Equation #4
At a constant temperature this may be written as Equation #5
We can use this result to describe the free energy of diffusion of a particular ion in our cell or outside of the cell as follows:
Equation #8
(G)= (RTln(cout) +zFEout) —(RTln(cin) + zFEin)
Which simplifies to:
Equation #9)
(G) = R.T.ln(cout/cin) + z.F.δ(E)
By definition at equilibrium DG = 0 thus the equilibrium potential for any given ion is given by:
21
We may usefully consider the path of current flow to determine the effect of neurite geometry on electrical characteristics
22
Models for channel gating
-t/v
deltaVm(t) = Im.R(1-e )
20
When we consider the passive electrical environment of axons or dendrites it is useful to
think of them as composite structures
Gelect = zFE
8
The free energy of ions inside or outside of the cell is the sum of these forces
So the free energy (G) inside or outside of the cell may be expressed as
Equation #10 δ(E) = RT/ZF ln(cin/cout)
This is the Nernst-Einstein equation.
9
Current flowing across the giant axon membrane may be represented by the sum of conductive components (What we now identify as ion channels) and capacitance (the cell membrane). The currents are described in the following circuit diagram.
23
26
27
谢谢你的阅读
知识就是财富 丰富你的人生
Thus Equation #2
pV=µRT
Now the work done by an expanding gas can be calculated as foll expands from an initial volume Vi to a final volume Vf. Using equation #2, we can see that the work done per mole is
If z =valency of ion E = electrical potential across the delimiting membrane.
Thus the electrical energy in a mole of an ion may be expressed as
Equation #1
Equation #6
Gdiff = RTln(c)
7
Electrical forces acting on an ion
According to Faraday the charge on a mole of material is 96483 z Coulombs where z is the charge of each atom or ion (the valency of an ion). This is the Faraday constant or F.
Equation #7 G = Gdiff + Gelect = RTln(c) + zFE
(from #1 and #2)
The difference between free energy inside the cell and outside defines the free energy driving movement of the ion across the cell membrane which may be expressed as follows: