1. Physiology as the science. Bioelectrical phenomena in excitable tissues

2. Defining of “physiology” notion
Physiology is the science about the regularities of organisms‘ vital activity in connection with the external environment.

3. Method of physiology a) Observation
This is the method in which the scientists don‘t mix in course of vital processes. They only make use of vision and description of all changes. On the base of this changes they make conclusions.
b) Experiment
There are two kinds of experiments: acute and chronic. Acute experiment was doing with the helps of anesthesia. It may be accompanied by cut off the nerves, introduction the different substances. The chronic experiment was doing in vital animals, for example, after the acute experiment scientists can used the observation.

4. Method of physiology c) Examination
This is the method of examine the patient with different diseases, for example, with using the different apparatuses.
d) Simulation
We can simulation different processes as a laboratory simulation or realistic simulation, for example, apparatus of artificial kidney or apparatus of artificial circulation. It may be the simulation the different processes by means of computers.

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

12. Basic Concepts Forces that determine ionic movement
Electrostatic forces
Opposite charges attract
Identical charges repel
Concentration forces
Diffusion – movement of ions through semipermeable membrane
Osmosis – movement of water from region of high concentration to low

13. Basic mechanisms of transport

14. Gating of protein channels provides a means of controlling ion permeability of the channels.

15. I. Membrane Resting Potential
A constant potential difference across the resting cell membrane
Cell’s ability to fire an action potential is due to the cell’s ability to maintain the cellular resting potential at approximately –70 mV (-.07 volt)
The basic signaling properties of neurons are determined by changes in the resting potential

16. Concept of Resting Potential (RP)
A potential difference across the cell membrane at the rest stage or when the cell is not stimulated.
Property:
It is constant or stable
It is negative inside relative to the outside
Resting potentials are different in different cells.

17. Resting Membrane Potential
Na+ and Cl- are more concentrated outside the cell
K+ and organic anions (organic acids and proteins) are more concentrated inside.

18. Active Transport
Movement of molecules and ions against their concentration gradients.
From lower to higher concentrations.
Requires ATP.
2 Types of Active Transport:
Primary
Secondary

19. Primary Active Transport
ATP directly required for the function of the carriers.
Molecule or ion binds to carrier site.
Binding stimulates phosphorylation (breakdown of ATP).
Conformational change moves molecule to other side of membrane.

20. 4. The Na+ diffuse away from the carrier protein.
Extracellular fluid
1. Three sodium ions (Na+) and adenosine triphosphate (ATP) bind to the carrier protein.
Carrier protein
Na+
Cytoplasm
ATP binding site 1
ATP
Na+ 3
2. The ATP breaks down to adenosine diphosphate (ADP) and a phosphate (P) and releases energy. K+
3. The carrier protein changes shape, and the Na+ are transported across the membrane.
Carrier protein changes
shape (requires energy) P
Breakdown of ATP
(releases energy) 2
ADP 4
4. The Na+ diffuse away from the carrier protein.
Na+ K+ 5
5. Two potassium ions (K+) bind to the carrier protein.
6. The phosphate is released. 6 P
Carrier protein resumes
original shape
7. The carrier protein changes shape, transporting K+ across the membrane, and the K+ diffuse away from the carrier protein. The carrier protein can again bind to Na+ and ATP. 7 K+

21. Intracellular vs extracellular ion concentrations
Ion Intracellular Extracellular
Na mM mM
K mM mM
Mg mM mM
Ca mM mM
H M (pH 7.2) M (pH 7.4)
Cl mM mM

22. Resting Membrane Potential
Potassium ions, concentrated inside the cell tend to move outward down their concentration gradient through nongated potassium channels
But the relative excess of negative charge inside the membrane tend to push potassium ions out of the cell

23. Resting Membrane Potential
Na+ is more concentrated outside than inside and therefore tends to flow into the cell down its concentration gradient
Na+ is driven into the cell by the electrical potential difference across the membrane.
But what about sodium?
Electrostatic and Chemical forces act together on Na+ ions to drive them into the cell
The Na+ channel close during the resting state

24. Resting Potential

26. Postulated mechanism of the sodium-potassium pump

27. The formation of resting potential depends on:
Concentration difference of K+ across the membrane
Permeability of Na+ and K+ during the resting state
Na+-K+ pump

28. Factors that affect resting potential
Difference of K+ ion concentration across the membrane
Permeability of the membrane to Na+ and K+.
Action of Na+ pump

29. Basic Electrophysiological Terms I:
Polarization: a state in which membrane is polarized at rest, negative inside and positive outside.
Depolarization: the membrane potential becomes less negative than the resting potential (close to zero).
Hyperpolarization: the membrane potential is more negative than the resting level.

30. Basic Electrophysiological Terms I:
Reverspolarization: a reversal of membrane potential polarity.
The inside of a cell becomes positive relative to the outside.
Repolarization: restoration of normal polarization state of membrane.
a process in which the membrane potential returns toward from depolarized level to the normal resting membrane value.

31. Effect of stimuli of increasing voltages to elicit an action potential

32. Typical action potential

34. II Action Potential Successive Stages: Resting Stage
Depolarization stage
Repolarization stage
After-potential stage
(2)
(3)
(1)
(4)

36. The Action Potential Components/characteristics RMP
Depolarizing stimulus
Threshold
Rapid Na+ entry (depolarization)
Isopotential
Overshoot
Repolarization (K+ moves out)
Undershoot (after-hyperpolarization)
Absolute refractory period
Relative refractory period

37. Propagation of action potentials in both directions along a conductive fiber

39. Saltatory conduction along a myelinated axon
Saltatory conduction along a myelinated axon. Flow of electrical current from node to node is illustrated by the arrows.