Electrical properties of cell tissues
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Electrical Properties of Cell & Tissues. 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

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Electrical Properties of Cell & Tissues

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Electrical Properties of Cell & Tissues


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


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


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


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


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.


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


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


Charges Across The Cell Membrane

  • Intracellular  high potassium (K+), low sodium (Na+)

  • Extracellular  low potasiom ,high sodium, hi calcium


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


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


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


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


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


Action Potential


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


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


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


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


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)


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


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


Pinocytosis

  • It is used by large molecules

  • Part of the cell membrane surround the molecule, then detaches itself in a vesicle into the cell


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


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


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


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


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


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


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


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


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


How Can We Use Bioelectricity

  • We can use it in two ways:

  • Evaluation

  • Treatment


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


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


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


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)


 Study Hard & Good Luck 


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