Electrical Properties of Cell
& Tissues
Lecture Objectives
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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
1.
Excitable tissue, like muscle & nerves
2. 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
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Each excitable cell has 4 electrical zones:
1.
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
2.
3.
4.
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 ?
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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
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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
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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:
1. Diffusion
2. Facilitated diffusion
3. Active transport
4. Pinocytosis
Diffusion
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1.
2.
3.
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
Differences Between Electric
& Biological Circuit
Biological circuit:
1. Electric charge in wet
environment
2. Atoms & ions
3. Components of circuit are always
changing
4. There is a continuous leakage
5. There need to be areas charge
differences
6. Short pathway
7. Energy is needed all the time
8. Slower, the response rate is in
millisecond
Electric circuit:
1. Electric charge in dry environment
2. Uses electrons
3. Need occasional replacement of
components
4. Move electric charges without
leakage (or there will be a shock)
5. Long pathway
6. Energy is needed only when the
circuit is working
7. Faster, the response rate is in
nanosecond
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:
1. Evaluation
2. Treatment
Evaluation
1.
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Electroencephalogram (EEG):
Used to record electrical activity of the brain
2.
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Electromyogram (EMG)
Used to observe the muscle function
3.
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Electrocardiogram (ECG)
Record the activity of the heart
Treatment
1.
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
1.
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 