1. Electrical properties of the cell membrane
Transduction of signals at the cellular level
Resting Membrane Potential
Action Potential
Olga Vajnerová
DEPARTMENT OF PHYSIOLOGY
Second Medical School Charles University Prague, Czech Republic

2. Transmission of the signal in NS
EPSP AP
Neurotransmitter releasing

3. Transmission of the signal along the skeletal muscle fibre

4. Cardiac Electrical Activation

5. Smooth muscle

6. Preliminary knowledge
Cell membrane
Na/K ATPase
Ion channels

7. Cell membrane Phospholipid bilayer
glycerol - fatty acids (hydrophobic)
- fosfate (hydrophilic)
Membrane does exist in the aqueous environment only.
Proteins peripheral
integral non penetrating
penetrating (transmembrane)

8. Cell membrane proteins peripheral
integral non penetrating
penetrating (transmembrane)

9. Integral penetrating cell membrane proteins
Na+- K+ pump

10. Extrudes 3 Na+ ions Brings 2 K+ ions in
Na+- K+ pump
Extrudes 3 Na+ ions
Brings 2 K+ ions in
Unequal distribution
of ions
Na+ and Cl - extracelullary
K+ and A- intracelullary

11. Ion channels Resting channels - normally open
Integral penetrating cell membrane proteins
Ion channels
Resting channels - normally open
Gated channels - closed when the membrane is at rest
opening is regulated by
1. Membrane potential (voltage gated)
2. Ligand (chemicaly gated)
3. Membrane potential plus ligand binding (Voltage and chemicaly gated)
4. Membrane stretch (mechanicaly gated)

12. Resting (nongated) channels
Potassium leak channel

13. Voltage gated potassium channel
Gated channels
Voltage gated potassium channel
Two states
Activated (open) After depolarisation
Resting (closed)

14. Voltage gated sodium channel
Gated channels
Voltage gated sodium channel
Three states:
Resting (closed)
After depolarisation
Activated (open)
Inactivated (closed)

15. Resting membrane potential
Every living cell
in the organism

16. Membrane potential is not a potential
Membrane potential is not a potential. It is a difference of two potentials so it is a voltage, in fact.

17. When the membrane would be permeable for K+ only

18. When the membrane would be permeable for K+ only
Na+
Cl-
Chemical driving force
Diffusion
Outward movement of K+

19. When the membrane would be permeable for K+ only
K+ escapes out of the cell along concetration gradient
A- cannot leave the cell
Greater number of positive charges is on the outer side of the membrane K+ Ai + - K+
Na+
Cl-

20. When the membrane would be permeable for K+ only
Greater number of positive charges is on the outer side of the membrane
electrical driving force emerges
inward movement of K+ K+ K+ K+

21. When the membrane would be permeable for K+ only
Chemical gradient equals electrical gradient
No net movement of ions
Steady state is balanced

22. When the membrane would be permeable for K+ only
Negative membrane potential
Equilibrium membrane potential for potassium

23. When the membrane would be permeable for Na+ only
Cl- ???
Membrane voltage positive ?
null ?
negative ?

24. When the membrane would be permeable for Na+ only
Na + influx into the cell
Cl- stay on the outer surface of the membrane
Stabilization of balance – equilibrium membrane potential
for sodium is positive

25. When the membrane would be permeable for Cl- only
Na +???
Membrane voltage positive ?
null ?
negative ?

26. When the membrane would be permeable for Cl- only
Cl- influx into the cell
Na + stay on the outer surface of the membrane
Stabilization of balance – equilibrium membrane potential
for chlorine is negative

27. Equilibrium potential for K+ and Na+
When the membrane would be permeable
for K+ only for Na+ only

28. How to calculate the magnitude of the membrane potential
R – universal gas constant
T – absolute temperature
Ce , Ci – ion concentration
E – potential difference
n – charge of ion
F – Faraday’s constant
Osmotic work
The work, which must be done to move 1 mol of the substance from concentration Ceto concentration Ci
Ao= R.T.ln [Ce] /[Ci ]
Electric work
The work, which must be done to move 1 mol of the substance across the potential difference E
Ae = E. n. F

29. How to calculate the magnitude of the membrane potential
When the systém is in balance then osmotic work equals electric work
R – universal gas constant
T – absolute temperature
Ce , Ci – ion concentration
E – potential difference
n – charge of ion
F – Faraday’s constant
Ao= Ae
R.T.ln [Ce] /[Ci ] = E. n. F
E =
Nernst equation
E = RT/nF . ln [Ce] /[Ci ]

30. Resting membrane potential
Membrane permeability
K : Na : Cl-
1 : ,03 : 0.1

31. Membrane permeability
K : Na : Cl-
1 : ,03 : 0.1
Goldman equation

32. Action potential Conductive Membranes: Axon of neurons
Skeletal muscle fibre
Smooth muscle cell
Heart muscle

34. Action potential
Membrane permeability
K : Na : Cl-
1 : : 0.1

35. Conductance of the membrane for Na+ and K+
Membrane potential
Depolarization
Achievment of threshold
Opening of voltage gated Na + chanels
AP overshoot to positive values
Conductance of the membrane for Na+ and K+

36. Terms
- Depolarisation
- Repolarisation
- Hyperpolarisation

37. Propagation of the action potential along the axon

38. Propagation of the action potential along the axon

39. Action potential - all or nothing law - propagation without decrement

40. Transmission of the signal in NS
Processing of information – local potential (in receptors)
- Action potentials
EPSP AP
Neurotransmitter releasing

41. Transmission of the signal along the skeletal muscle fibre
AP – T tubulus – DHPR receptor – RYR receptor – Ca2+
axon
Muscle fiber
Neuromuscular junction

42. Cardiac Electrical Activation

43. Smooth muscle Multiunit
Single unit (unitary) – Nerve fiber - varicosity
Receptors on the muscle surface
gap junctions

44. Thanks for your attention
The end
Thanks for your attention
The seed was planted 
Questions ??? Comments ???