2.4.lecture 4BelSU  Institute of Medicine Department Biomedical Sciences

1. Student's uniform
Форма студентов на лекции !

2. Lecture № 3
Introduction to
Electrophysiology
Введение в электрофизиологию
September 7, 2019
BelSU. Institute of Medicine.
Code and name of course
31.05.01 General Medicine
2019/2020 academic year

3. • Prepare a checklist (diagram A5).
• Sign: group number, name, date.
• Give checklist the lecturer at the end
of the lecture with answers to the
lecturer's questions.

4. Литература основная
Guyton And Hall Textbook Of
Medical Physiology
P. 57–65,
66-67

5. P.P.64 – 70
Guyton & Hall
Textbook Of
Medical Physiology
• A South Asian
Edition
• 2013

6. Definition of
Electrophysiology
Question No 1.

7. Physiology of Excitable
Tissues
≈ Electrophysiology

8. Electrophysiology
• is the study of the electrical
properties of biological cells
and tissues.

9. Electrophysiology
• involves measurements of
voltage change or electric
current on a wide variety of
scales from single ion
channel proteins to whole
organs.

10. Electrophysiology
from Greek
• ἥλεκτρον, ēlektron, "amber" [see the
etymology of "electron"];
• φύσις, physis, "nature, origin"; and -λογία, -
logia)

11. A study of the
bioelectric
phenomena in living
tissues
Question No 2.

12. Animal electricity and the
birth of electrophysiology:
The legacy of Luigi Galvani
2.1

13. Luigi Aloisio Galvani
• 1737 – 1798
• was an Italian
physician, physicist
and philosopher
• Founder of
electrophysiology
• he discovered “animal
electricity”

14. Luigi Galvani's monument in
Piazza Luigi Galvani (Luigi
Galvani Square), in Bologna

15. The 1st Galvani’s
experiment
2.1.1

16. • During the 1780's,
biologist Luigi
Galvani performed
experiments at the
University of
Bologna involving
frogs.

17. • While cutting a frog’s
leg, Galvani's steel
scalpel touched a
brass hook that was
holding the leg in
place.
• The leg twitched.

18. The 1st Galvani’s experiment

19. The 1st Galvani’s experiment

20. The 1st Galvani’s experiment

21. • Further experiments confirmed this effect,
and Galvani was convinced that he was
seeing the effects of what he called
• animal electricity,
• the life force within the muscles of the frog.

22. • At the University of Pavia,
Galvani's colleague Alessandro
Volta was able to reproduce the
results,
• but was skeptical of Galvani's
explanation.

23. Alessandro Giuseppe Antonio
Anastasio Volta
• 1745 – 1827
• was
an Italian physicist kn
own for the invention
of the battery in the
1800s.

24. • By experiment Volta found that
it was the two dissimilar metals,
not the frog’s leg that produced
the electicity.
• The frog’s leg was just an
indicator of presence of the
electricity.

25. Aldini electrifies the body of a
"malefactor" (London, 1803)

26. A.Volta
• demonstrated that it was the wires in the
solution, rather than animal tissue, that
generated electric current.
• constructed the first galvanic cell, and later
stacked cells to form what became known
as ‘Volta’s pile’.
• Volta discovered «chemical electricity»,
chemical sources of electric current

27. The 2nd Galvani’s
experiment
2.1.2

28. The 2nd Galvani’s experiment
•without metal !!!

29. The 2nd Galvani’s experiment
Cut across the hip muscle of
the other leg of the frog
Place the buttock’s nerve of
the paw in the cross-section on
the leg muscle and observe the
reaction

30. Prepare the
rheoscopic leg
of the frog.
The 2nd Galvani’s experiment

31. sciatic nerve
+
calf muscle of
frog's leg
Neuromuscular rheoscopic leg:

32. Cut across the
hip muscle of
the other leg of
the frog
The 2nd Galvani’s experiment

33. Place the sciatic
nerve
(buttock’s nerve)
of the
rheoscopical paw
in the cross-
section on the leg
muscle and
observe the
reaction.
The 2nd Galvani’s experiment

34. Throw the nerve of
the rheoscopic leg
on the muscle cut
and the adjacent
area of the intact
muscle segment.
The 2nd Galvani’s experiment

35. The 2nd Galvani’s experiment

36. • When napping a nerve, excitement
• (action potential) occurs in the nerve fibers
that come in contact with the muscle cut
(cathode).

37. • When the nerve is released, agitation
• (action potential) arises in the nerve fibers
that come in contact with the intact muscle
region (anode).
• This anodic-staging excitation by E.Pfluger
(1859)

38. L. Galvani
• discovered something he
named "animal electricity“
• first registered a membrane
potential by method damage.
Key points:

39. Membrane potential
Question No 3.

40. Membrane potential :
Definition
3.1

41. Membrane potential
• also transmembrane potential or membrane
voltage
• is the difference in electric potential
between the interior and the exterior
of a biological cell.

42. What is the membrane
potential?

43. What is the membrane
potential?

44. What is the membrane
potential?

45. What is the membrane
potential?

46. What is the membrane
potential?

47. Do not speak!
• Membrane Potential is the difference
in electric potential between the
inner surface and outer surface of
the cell membrane.
• The electrical charge of the cell
membrane itself is different from the
transmembrane potential:
on the external surface it is negative, and
on the inner surface it is positive.

48. Membrane Potential
• is the difference in
electric potential
between
intracellular fluid and
extracellular fluid.

49. • Let's place the electrodes in different parts
of the cytosol and the external solution.
• MP does not change.

50. • A graph of the
voltage
recorded
between a
movable
micropipette
electrode and a
fixed electrode
in the
extracellular
fluid (ordinate)
against time
(abscissa).

51. • At the origin,
both the pipette
and the fixed
electrode are in
the
extracellular
fluid, and the
voltage
between them
is zero (A).

52. • When the
micropipette
penetrates the
membrane, the
voltage changes
to -70 mV,
inside with
respect to
outside (B).

53. • When the
electrode is
backed out of
the cell, the
potential
returns to zero
(C).
• The positions of VNa+
and VK+ are indicated
on the ordinate.

54. Measurement of the
membrane potential of cells
and fibre
3.2

55. Measurement of the membrane
potential of cells and fibre using …
• a damage
• a microelectrode

56. • When using the damage method,
a cut of many cells is made

57. L. Galvani
• first registered a membrane
potential by method damage.
Key points:

58. Measurement of the membrane potential of the
nerve fiber using a microelectrode

59. Measurement of the membrane
potential of the nerve fiber using a
microelectrode

60. • Intracellular recording involves measuring
voltage and/or current across the membrane
of a cell.

61. Resting Membrane Potential
(RMP)
Question No 4.

62. Resting Membrane Potential:
Definition
4.1

63. Resting Membrane Potential
(RMP)
• The relatively static
membrane potential of
quiescent cells is called the
resting membrane potential
(or resting voltage),
• as opposed to the specific dynamic
electrochemical phenomena called action
potential and graded membrane potential.

64. The Resting
Membrane Potential
of cells is negative
always.

65. • Typical values of membrane potential range
from –40 mV to –90 mV.

66. The resting membrane potential in
different cell types are
approximately:
• Skeletal muscle cells: − 95 mV
• Smooth muscle cells: – 60mV
• Astroglia: – 80 to – 90mV
• Neurons: – 60 to –70mV
• Erythrocytes: – 9mV

67. Resting Membrane Potential:
Generation
4.2

68. Calculation of the MP When the
Membrane Is Permeable to
Several Different Ions
RMP depends on three factors:
1. the polarity of the electrical charge of
each ion,
2. the permeability of the membrane to
each ion,
3. the concentrations of the respective
ions on the inside and outside of the
membrane.

71. The Goldman–
Hodgkin–Katz voltage
equation
• is used in cell
membrane physiology to determine
the reversal potential across a cell's
membrane, taking into account all
of the ions that are permeant
through that membrane.

72. The Goldman–Hodgkin–Katz
voltage equation
• Goldman equation
• GHK equation

73. GHK equation
The discoverers of this are
• David E. Goldman of Columbia
University,
• and the English Nobel laureates
Alan Lloyd Hodgkin and Bernard
Katz.

76. The main mechanism for generating
the resting potential is
• The main mechanism for generating resting
potential creating an asymmetry of the
concentration of K+ using a sodium-
potassium pump (ATPase)
• the conclusion of K+ from the cell through
potassium leakage channels
• anions do not leave the cell
• other cations do not enter the cell

77. Electrogenic Nature of the Na+-K+
Pump
• The Na+-K+ pump moves 3 Na+ to the
exterior for every 2 K+ to the interior means
that a net of one positive charge is moved
from the interior of the cell to the exterior
for each cycle of the pump.
• Therefore, the Na+-K+ pump is said to be
electrogenic because it creates an electrical
potential across the cell membrane.

78. Postulated mechanism of the
sodium-potassium pump

87. Functional characteristics of the Na+-K+
pump and of the K+-Na+ “leak” channels.

89. Types of membrane
potential changes
Question No 5.

90. • After a cell has established a resting
potential, that cell has the capacity to
undergo depolarization and
hyperpolarization.

91. Types of membrane potential
changes:
• Depolarization
• Hyperpolarization
• Repolarization

93. Depolarization
• represents a change within the cell during
which the cell undergoes a shift in the
distribution of the electric charge, which
results in a smaller negative charge inside
the cell.

94. Hyperpolarization
• is a change within the cell during which the
cell undergoes a shift in the distribution of
the electric charge, which leads to a greater
negative charge within the cell.

95. Repolarization
• is the return of the charge to the initial value
(rest potential).

96. Изменения пот енциала покоя

97. Types of membrane potential changes.
• Decrease of MP level is
depolarization
(MP becomes less negative)
• Increase of MP level is
hyperpolarization
(MP becomes more negative)

98. • Decrease of MP level is depolarization =
Increase of MP
• Increase of MP level is hyperpolarization =
Decrease of MP

99. Action Potential (AP)
Question No 6.

100. The Action Potential (AP)
• is specific changes in the membrane
potential as a manifestation of the excitation
of an excitable cell.

102. Action potentials

105. The period of exaltation according to NEVvedensky

107. Ionic mechanism of action
potential formation.
Question No 7.

130. Establishment of resting membrane potentials
in nerve fibers under three conditions:

131. Establishment of resting membrane potentials
in nerve fibers under three conditions:
when the membrane potential is caused by
diffusion of …
• A, … potassium alone ;
• B, … both sodium and potassium ions;
• C, … both sodium and potassium ions +
pumping of both these ions by the Na+-K+
pump.

132. In summary, the diffusion potentials
alone caused by potassium and sodium
diffusion would give a membrane
potential of about
• –86 millivolts, almost all of this being
determined by potassium diffusion.
• –4 millivolts is contributed to the membrane
potential by the continuously acting
electrogenic Na+-K+ pump, giving a net
membrane potential of –90 millivolts.

135. Changes in sodium and potassium
conductance during the course of the
action potential.

136. Ходжкин