2. Typical values
These differences
result in a
resting potential

3. Membrane potentials are based upon the unequal permeability of the membrane to different ions
Ions are not distributed equally across a membrane

4. Pumps maintain the membrane in a steady-state
This is NOT an equilibrium!

5. More positive charges here
difference across here is
membrane potential
More negative
charges here
More positive charges here

6. X+ is present at 1 M in chamber A and at 0. 1 M in chamber B
X+ is present at 1 M in chamber A and at 0.1 M in chamber B. A concentration force for X+ tends to cause X+ to flow from A to B. However, chamber A is electrically negative with respect to chamber B, so an electrical force tends to cause X+ to flow from B to A.

7. A membrane separates chambers containing different K+ concentrations
A membrane separates chambers containing different K+ concentrations. At an electrical potential difference (EA - EB) of -60 mV, K+ is in electrochemical equilibrium across the membrane.

8. A membrane separates chambers that contain different HCO3- concentrations. EA - EB = +100 mV.
HCO3- is not in electrochemical equilibrium. If EA - EB were +60 mV, HCO3- would be in equilibrium. EA - EB (+100 mV) is stronger than it needs to be (+60 mV) to just balance the tendency for HCO3- to move from A to B because of its concentration difference. Thus, net movement of HCO3- from B to A will occur.

9. A, Before a Gibbs-Donnan equilibrium is established, a membrane separates two aqueous compartments.
B, Ion concentrations after Gibbs-Donnan equilibrium has been attained.

10. A hydrostatic pressure of 2
A hydrostatic pressure of 2.99 atmospheres is required to prevent water from flowing from chamber B to chamber A in the Gibbs-Donnan equilibrium. This 2.99 atmosphere is equal to the osmotic pressure in chamber A minus that in chamber B.

11. A, A concentration cell. A membrane, separates KCl solutions of different concentrations. B, The concentration cell after electrochemical equilibrium has been established.
The flow of an infinitesimal amount of K+ generated an electrical potential difference across the membrane that is equal to the equilibrium potential for K+.

12. برقراری پتانسيل انتشار در غشای فيبر عصبی به صورت شماتيک

13. Where EX is the chemical potential and z is the charge of ion X
THE NERNST EQUATION
The cytoplasmic and extracellular concentrations of an ion
determine the chemical driving force for that ion and
the equilibrium membrane potential if this is the ONLY ion
that is permeable through the membrane
EX =
58 mV z
log
[X]out
[X]in
Nernst Equation
Where EX is the chemical potential and z is the charge of ion X
z = +1
[K+]in = 130 mM
[K+]out = 5 mM
For potassium:
58 mV 5
EK+ =
log
= mV 1
130

14. RESTING POTENTIAL SET BY RELATIVE PERMEABILITIES
OF K+, Na+, & Cl- IONS
Nernst Potential Relative Permeability (P)
EK = mV
ENa = mV
ECl = mV
Resting membrane potential reflects the relative permeabilities
of each ion and the Nernst potential of each ion
PK EK + PNa ENa + PCl ECl
PK + PNa + PCl
Vm =
When the resting membrane potential is achieved, there is
ongoing influx of sodium and a matching efflux of potassium.
Na/K ATPase is continually needed to keep the ion gradients
from running down over time

15. PK[K+]o + PNa[Na+]o + PCl[Cl-]i PK[K+]i + PNa[Na+]i + PCl[Cl-]o
THE GOLDMAN EQUATION
PK EK + PNa ENa + PCl ECl
PK + PNa + PCl
Vm =
from before
EX =
58 mV z
log
[X]out
[X]in
Nernst equatiion
Vm = 58 mV log10
PK[K+]o + PNa[Na+]o + PCl[Cl-]i
PK[K+]i + PNa[Na+]i + PCl[Cl-]o ( )
Goldman equation
The greater an ion’s concentration and permeability, the more
it contributes to the resting membrane potential
When one ion is by far the most permeable, Goldman eq. reduces to Nernst eq.

16. PK[K+]o + PNa[Na+]o + PCl[Cl-]i PK[K+]i + PNa[Na+]i + PCl[Cl-]o
THE GOLDMAN EQUATION & THE RESTING POTENTIAL ) (
PK[K+]o + PNa[Na+]o + PCl[Cl-]i
Vm = 58 mV log10
PK[K+]i + PNa[Na+]i + PCl[Cl-]o
[K+]o
= 5 mM
[Na+]o
= 145 mM
[Cl-]o
= 100 mM
[K+]i
= 130 mM
[Na+]i
= 5 mM
[Cl-]i
= 8 mM PK
= 1
PNa
= 0.05
PCl
= 0.2
Vm = mV

17. Rest During Action Potential
INCREASING SODIUM PERMEABILITY UNDERLIES SODIUM INFLUX
AND MEMBRANE DEPOLARIZATION DURING ACTION POTENTIAL
During action potential, the number of open sodium channels increases dramatically
EK = - 82 mV
ENa = + 85 mV
ECl = - 64 mV
Nernst Potential Prest Paction-potential
Rest During Action Potential
- 70 mV
+ 36 mV
GOLDMAN EQUATION-PREDICTED Vm
When sodium channels open, sodium ions flow in rapidly because of the
negative membrane potential and the strong inward sodium battery
Inward sodium current depolarizes membrane and moves it towards the
positive potential predicted by Goldman’s equation
(this positive potential is never fully achieved due to additional channel dynamics)

19. اندازه گيری پتانسيل غشای فيبر عصبی با کمک ميکروالکترود

21. پمپ سديم پتاسيم و کانالهای نشتی سديم، پتاسيم

22. برقراری پتانسيل استراحت در سه حالت: A) زمانی که پتانسيل غشاء صرفا“ ناشی از انتشار K+ باشد. B) ناشی از Na+ و K+ باشد. C) ناشی از Na+، K+ و پمپ سديم پتاسيم باشد.

23. پتانسيل عمل ثبت شده (به صورت شماتيک)

24. ويژگی کانالهای سديمی و پتاسيمی (وابسته به ولتاژ بودن)

25. Na Selectivity Filter

26. روش voltage clamp برای مطالعه جريان يون از کانال های خاص

27. تغيير هدايت کانالهای سديمی و پتاسيمی در زمان ايجاد پتانسيل عمل

28. تغييرات هدايت سديم و پتاسيم در طی پتانسيل عمل
نسبت هدايت سديم به پتاسيم

29. روش Patch clamp برای مطالعه کانالهای يونی غشاء سلول در حالتهای مختلف

31. Action Potential (HyperPhysics, Georgia State University)

32. گسترش پتانسيل عمل در هر دو جهت طول يک فيبر هدايتی

33. Action Potential Propagation (BiologyMad.com)

34. Action Potential Propagation (BiologyMad.com)

35. Action Potential Propagation (BiologyMad.com)

36. Action Potential Propagation
myelin
stealth
Ranvier nodes
(ion channels only)
axon
nerve cell

37. توليد حرارت در فيبر عصبی در حالت استراحت و حالت تحريک

38. پتاسيل عمل کفه دار

39. پتانسيل عمل ريتميک

40. آکسون، سلول شوان و غلاف ميلين

41. هدايت جهشی در طول آکسون ميلين دار

42. Transmission of a nerve impulse

43. The passive spread of
an electrical signal

44. Conduction down the axon is
fundamentally different
It proceeds by saltatory jumps

45. SODIUM CHANNELS ONLY AT NODES
ROLE OF MYELIN IN FAST ELECTRICAL TRANSMISSION
Unmyelinated
Axon
(SLOW CONDUCTION)
Myelinated
Axon
(FAST CONDUCTION)
SODIUM CHANNELS ONLY AT NODES
AT VERY HIGH DENSITY
Action potential at one point along unmyelinated axon produces current that only
propagates short distance along axon, since current is diverted through channels
in axon membrane. So action potential can only next occur short distance away
Myelin reduces effective conductance and capacitance of
internodal axon membrane. (how???)
Action potential at node of Ranvier produces current that propagates
0.5-5 mm to next node of Ranvier, generating next action potential

46. اثر محرکها بر پتانسيلهای غشاء تحريک پذير

47. اسيلوسکوپ اشعه کاتدی برای ثبت پتانسيلهای عمل گذرا

48. Figure 3-11 The action potential of nerve and the associated absolute and relative refractory periods.
© 2005 Elsevier

49. تزريق جريان و ثبت تغييرات پتانسيل غشاء

50. A, Responses of an axon of a shore crab to a subthreshold rectangular pulse of current recorded extracellularly by an electrode located different distances from the current-passing electrode. As the recording electrode is moved farther from the point of stimulation, the response of the membrane potential is slower and smaller.
© 2005 Elsevier

51. حافظ از باد خزان در چمن دهر مرنج فکر معقول بفرما گل بی خار کجاست