Electrical Properties of Cell & Tissues

1. Electrical Properties of Cell & Tissues

2. Lecture Objectives • Cell physiology • Electrical zones of the cell • Effect of changing the electrical environment of the nerve • Identify methods of ion transfer across cell membrane • Identify differences between electric & biological circuit • Explain causes & importance of current of injury • Discuss causes & importance of strain potential • Discuss the uses of bioelectricity

3. Cell physiology • The cell is the functional unit in organisms, it is the building block of the body • The cell is very very small • Cell membrane is composed of a a bilayer of phospholipids • Cell membrane is almost 5 – 5.7 nm

4. Cell physiology • Inside the cell there are electrical charges, these electrical charges move inside and outside of the cell • Some of the electrical charges are bound to be inside • Cells usually are bind together by junctions, forming tissues

5. Types of Tissue • Excitable tissue, like muscle & nerves • Non-excitable tissues, they have charges but the can not be stimulated like excitable tissues, e.g. skin, bone, adipose tissue, connective tissue & epithelial tissue

6. Electric Charges • Electric charges can be found either single or compound (multiple) • They can be found inside the cell or outside the cell • Because some ions are able to move from the inside to the outside or from the outside to the inside, they are creating what we call a the convection current.

7. Zones of The Cell • Each excitable cell has 4 electrical zones: • The innermost zone (central zone ) which is negative because it has proteins & amino acids • The inner zone, it is positive, it has cations such as potassium • The outer zone, it is positive, it has ions such as sodium, calcium and potassium • The outermost zone which is negative, it has glycolipids

8. Zones of The Cell • the most two important layers are the two negative layers • These two layer are responsible for the electrical charges of the cell, the are the ones which change the cell properties

9. Charges Across The Cell Membrane • Intracellular  high potassium (K+), low sodium (Na+) • Extracellular  low potasiom ,high sodium, hi calcium

10. Why Electricity of The Cell Is Important ? • It is one way in which the cells communicate with each other • Signals come to the cell in a form of electric charges • Failure in this communication will result in disease or malfunction • In order to correct that disease we give external electricity • When we treat patient with electric modalities we are trying to correct that electrical charges within the cell

11. Why Electricity of The Cell Is Important ? • Normally, the signals come to the cell thought what we call a first messenger (hormone or neurotransmitter) • When these signals reaches the cell it activates the second messenger (enzymes or calcium) • This will result in a change in cell function

12. Why Electricity of The Cell Is Important ? • In case of a disease the problem lies in the first messenger • We apply electricity to work as first messenger • So, electricity will activate the second messenger & will change cell function & will correct the disease

13. Resting Membrane Potential • The difference in potential across the cell membrane is what causes the resting membrane potential • Inside is more negative than the outside • Resting membrane potential for skeletal muscle is -80 • Resting membrane potential for nerve & smooth muscle is -70

14. Action Potential • First there is a stimulus (hormone, neurotransmitter, mechanical stimulus) • Then we have Depolarization, channels are open , ion are rushed in inside the cell • It reaches a peak then goes down (Repolarization) • Then we have a refractory period, in which the cell can not be stimulated again • Then back to the resting membrane potential

15. Action Potential

16. Action Potential • Action potential results from a chemical, electrical stimulus • To have an action potential the difference shouldn't be less than 15 from the original value of resting membrane potential (e.g. reversal of membrane potential from -90 to +30) • All or none (either there is an action potential or there isn’t

17. Nerve Impulse • Information come to the nerve through dendrites  nucleus of the cell  axon  dendrites of the other cell • Saltatory transmission happens in mylenated axons, the myelin sheath form nodes of Ranvair • Impulses within the nerve move in one direction orthodromic • If we stimulate a nerve artificially the signal will move in 2 directions, either orthodromic or antidromic

18. Nerve Impulse • The characteristics of the nerve determines the nature of the nature & the speed of the impulse • If we have large diameter nerve conduction will be faster • If we have a mylenated axon conduction will be faster

19. Movement of Ions Across The Cell Membrane • There are 4 methods in which ions could move across the cell membrane: • Diffusion • Facilitated diffusion • Active transport • Pinocytosis

20. Diffusion • It is a passive process, usually small ions use this method to move across the cell, it moves from high concentration to low concentration • The rate of concentration is governed by factors such as: • Ion concentration, • Temperature (temperature diffusion) • Electrical charges (repulsion & attraction between charges)

21. Facilitated Diffusion • A passive process • Molecules attached to protein carriers to pass through the membrane • Large molecules such as glucose & amino acid use this methods for transfer

22. Active Transport • An active process, energy is needed, it comes from ATP • Ions and molecules are moving against their concentration and electrical charges • We have pumps that will help them move across the membrane (e.g., Na+ pumps, K+ pumps) • Sodium, potassium, calcium, hydrogen & chloride, use this method of transport

23. Pinocytosis • It is used by large molecules • Part of the cell membrane surround the molecule, then detaches itself in a vesicle into the cell

24. Biological circuit: Electric charge in wet environment Atoms & ions Components of circuit are always changing There is a continuous leakage There need to be areas charge differences Short pathway Energy is needed all the time Slower, the response rate is in millisecond Electric circuit: Electric charge in dry environment Uses electrons Need occasional replacement of components Move electric charges without leakage (or there will be a shock) Long pathway Energy is needed only when the circuit is working Faster, the response rate is in nanosecond Differences Between Electric & Biological Circuit

25. Current of Injury • It occurs when there is a wound in the skin, always found in & around the traumatized & healing area • The skin has charges, the positive charges in the skin move to the site where there is a cut or a wound • It happens a distance of 3mm from the open wound the wound • This movement is associated with closure in the wound

26. Current of Injury • If there is large amount of current in the wound the closure will be faster • If there is a minimal current the closure will take longer • one of the factors that helps in closing the wound faster is moist • If the wound is most  current will be higher  closure will be faster

27. Strain Potential • Strain potential can be found when there is mechanical deformation, either compression or distraction • When there is compression there will be negative charge • When there is distraction there will be positive charge • Strain potential increase bone growth

28. Strain Potential • If we have a broken bone & they placed electrodes on either side of this bone, there will be a current • When we put pressure on the bone, the area where the bone is convex (distracted) the charge will be positive • The are where the bone in concave (compresses) the charge will be negative

29. Strain Potential • Strain potential may increase bone growth • Signals instruct cells to either increase or decrease formation • The current also forms in the connective tissue  remodeling of connective tissue alignment

30. Strain Potential • Scientist observed that the skin has a negative current compared to lower layers (dermis, epidermis) • Normally in bones, the midpoint is positive, and the periphery is negative • Scientist observed that there are positive charged areas around the brain, brachial & lumber plexuses, while the peripheries have negative charges

31. Strain Potential • Scientist observed that the circuit within the bone is affected by the metabolism of the body • Scientist observed that when they applied electricity on small animals, they can control where the head & tail grow

32. Strain Potential • The scientist put electrodes on the salamander’s tail to study it, normally there was a very low current, but once they cut it there will be charges & the current will increase & the tail will start to grow • The scientist put electrodes on the frog’s tail to study it, normally there was a minimal current, and once they cut it there wasn’t a change & the tail didn’t grow

33. How Can We Use Bioelectricity • We can use it in two ways: • Evaluation • Treatment

34. Evaluation • Electroencephalogram (EEG): • Used to record electrical activity of the brain • Electromyogram (EMG) • Used to observe the muscle function • Electrocardiogram (ECG) • Record the activity of the heart

35. Treatment • In some disease the second messenger may not be working because it is not getting impulses from the first messenger • We give electricity to act as a first messenger to initiate or change cell function • Frequency window: some cells are sensitive to certain frequencies of electromagnetic field

36. Treatment • In some disease their could be a first messenger but the signals the cell receiving are weak • The applied energy may strengthen the weak current to result in strong signals that could modify cell function

37. Other Therapeutic Uses • To educate a nerve or a muscle • To relief pain & other symptoms (spasm, swelling edema) • Improve neural growth (inflammation around the nerve) • Heating tissues • When giving some drugs (iontopherisis)

38.  Study Hard & Good Luck 