Answer A There are two modes of tissue injury in electrical contacts: thermal injury and electroporation.Thermal injury, resultant from resistive heating of tissues, is a proportional response to tissue resistance, current density and duration of contact. Thermal injury occurs only along the current pathway. Given the energy requirements to heat tissue and the time constraints for heat diffusion, remote injury from tissue heating is often very limited High voltage, short pulsed electric fields (PEF) is a non-thermal ablation method, in which defined PEF irreversibly destabilize cell membranes, while preserving other tissue components such as the extracellular matrix (ECM) Tissue damage after electrical injury is mediated either thermally or electrically.When electricity passes through a solid conductor, heat is generated in proportion to the current strength, the duration of the current flow, and the resistance of the conductor. The greatest resistance encountered by the flow of current through the body is across the skin; this accounts for the burns and local coagulative tissue injury often seen at the points of electrical entry and exit. When electrical contact is brief, thermal injury and burns may be minimal but non-thermal injury may still cause damage by direct electrical effects causing electroconformational changes in membrane proteins, and the formation of pores in the cell membrane—electroporation.The vulnerability of a cell to non-thermal electrical damage is particularly related to its length in the direction of the electrical field, larger transmembrane potentials being induced in longer cells. Skeletal muscle cells and, particularly, nerve axons are thus especially susceptible to this type of non-thermal damage, which may disrupt peripheral nerve axons in isolation and in the absence of significant damage to surrounding tissue.The remarkable degree of peripheral nerve regeneration and recovery seen in this patient suggests that the axons were selectively injured, leaving the surrounding tissue including the Schwann cells intact to enable subsequent regeneration. This pattern of injury is consistent with acute non-thermal electrical injury. Answer B pH change is completely neutralized by the tissue buffer. Tissue injuries are evidenced as light red halos surrounding central red spots in the mucosa (corresponding to points where electrodes were placed). These injury halos can be the consequence, at least partially, of the extreme pH changes induced by the electric pulses applied. Answer C The severity of electrical injuiry depends on the type of source, the intensity of the current, the pathway through the body and the duration of the contact. Other factors are the applied current frequency , the phase of the heart cycle when the shock occurs and the general health ststus of the person. The effect of electrical shock decreases with applied signal frequency. High frequency currents donot exite muscles and do not cause cardiac arrhy.

1. Answer A
There are two modes of tissue injury in electrical contacts: thermal injury and
electroporation.Thermal injury, resultant from resistive heating of tissues, is a proportional
response to tissue resistance, current density and duration of contact. Thermal injury occurs only
along the current pathway. Given the energy requirements to heat tissue and the time constraints
for heat diffusion, remote injury from tissue heating is often very limited
High voltage, short pulsed electric fields (PEF) is a non-thermal ablation method, in which
defined PEF irreversibly destabilize cell membranes, while preserving other tissue components
such as the extracellular matrix (ECM)
Tissue damage after electrical injury is mediated either thermally or electrically.When electricity
passes through a solid conductor, heat is generated in proportion to the current strength, the
duration of the current flow, and the resistance of the conductor. The greatest resistance
encountered by the flow of current through the body is across the skin; this accounts for the
burns and local coagulative tissue injury often seen at the points of electrical entry and exit.
When electrical contact is brief, thermal injury and burns may be minimal but non-thermal injury
may still cause damage by direct electrical effects causing electroconformational changes in
membrane proteins, and the formation of pores in the cell membrane—electroporation.The
vulnerability of a cell to non-thermal electrical damage is particularly related to its length in the
direction of the electrical field, larger transmembrane potentials being induced in longer cells.
Skeletal muscle cells and, particularly, nerve axons are thus especially susceptible to this type of
non-thermal damage, which may disrupt peripheral nerve axons in isolation and in the absence of
significant damage to surrounding tissue.The remarkable degree of peripheral nerve regeneration
and recovery seen in this patient suggests that the axons were selectively injured, leaving the
surrounding tissue including the Schwann cells intact to enable subsequent regeneration. This
pattern of injury is consistent with acute non-thermal electrical injury.
Answer B
pH change is completely neutralized by the tissue buffer.
Tissue injuries are evidenced as light red halos surrounding central red spots in the mucosa
(corresponding to points where electrodes were placed). These injury halos can be the
consequence, at least partially, of the extreme pH changes induced by the electric pulses applied.
Answer C
The severity of electrical injuiry depends on the type of source, the intensity of the current, the
pathway through the body and the duration of the contact. Other factors are the applied current
frequency , the phase of the heart cycle when the shock occurs and the general health ststus of
the person.

2. The effect of electrical shock decreases with applied signal frequency. High frequency currents
donot exite muscles and do not cause cardiac arrhythmias.
Typical effects of electrification of the human body by 50 or 60 Hz AC current.
Type of Circuit and discussions
One of the factors affecting the nature and severity of electrical injury is the type of circuit
involved, either direct current (DC) or alternating current (AC).
High-voltage DC contact tends to cause a single muscle spasm, often throwing the victim from
the source. This results in a shorter duration of exposure but increases the likelihood of traumatic
blunt injury.
Brief contact with a DC source can also result in disturbances in cardiac rhythm, depending on
the phase of the cardiac cycle affected, the electrophysiologic principle used with cardiac
defibrillators.
AC exposure to the same voltage tends to be three times more dangerous than DC. Continuous
muscle contraction, or tetany, can occur when the muscle fibers are stimulated at between 40 and
110 times per second.
Unfortunately, the frequency of electrical transmission used in the United States is 60 Hz, which
is near the lowest frequency at which an incandescent light will appear to be continuously lit.
The terms entry and exit are commonly used to describe electrical injuries.
The terms source contact point and ground contact point, however, are more appropriate when
referring to AC injuries.
The hand is the most common site of contact via a tool that is in contact with an AC electric
source. Since the flexors of the hand and forearm are much stronger than the extensors,
contraction of the flexors at the wrist, elbow, and shoulder will occur, causing the hand grasping
the current source to pull the source even closer to the body. Currents greater than the “let-go
threshold” (6 to 9 mA) can prevent the victim from releasing the current source, which prolongs
the duration of exposure to the electrical current.
Solution
Answer A
There are two modes of tissue injury in electrical contacts: thermal injury and
electroporation.Thermal injury, resultant from resistive heating of tissues, is a proportional
response to tissue resistance, current density and duration of contact. Thermal injury occurs only
along the current pathway. Given the energy requirements to heat tissue and the time constraints
for heat diffusion, remote injury from tissue heating is often very limited
High voltage, short pulsed electric fields (PEF) is a non-thermal ablation method, in which

3. defined PEF irreversibly destabilize cell membranes, while preserving other tissue components
such as the extracellular matrix (ECM)
Tissue damage after electrical injury is mediated either thermally or electrically.When electricity
passes through a solid conductor, heat is generated in proportion to the current strength, the
duration of the current flow, and the resistance of the conductor. The greatest resistance
encountered by the flow of current through the body is across the skin; this accounts for the
burns and local coagulative tissue injury often seen at the points of electrical entry and exit.
When electrical contact is brief, thermal injury and burns may be minimal but non-thermal injury
may still cause damage by direct electrical effects causing electroconformational changes in
membrane proteins, and the formation of pores in the cell membrane—electroporation.The
vulnerability of a cell to non-thermal electrical damage is particularly related to its length in the
direction of the electrical field, larger transmembrane potentials being induced in longer cells.
Skeletal muscle cells and, particularly, nerve axons are thus especially susceptible to this type of
non-thermal damage, which may disrupt peripheral nerve axons in isolation and in the absence of
significant damage to surrounding tissue.The remarkable degree of peripheral nerve regeneration
and recovery seen in this patient suggests that the axons were selectively injured, leaving the
surrounding tissue including the Schwann cells intact to enable subsequent regeneration. This
pattern of injury is consistent with acute non-thermal electrical injury.
Answer B
pH change is completely neutralized by the tissue buffer.
Tissue injuries are evidenced as light red halos surrounding central red spots in the mucosa
(corresponding to points where electrodes were placed). These injury halos can be the
consequence, at least partially, of the extreme pH changes induced by the electric pulses applied.
Answer C
The severity of electrical injuiry depends on the type of source, the intensity of the current, the
pathway through the body and the duration of the contact. Other factors are the applied current
frequency , the phase of the heart cycle when the shock occurs and the general health ststus of
the person.
The effect of electrical shock decreases with applied signal frequency. High frequency currents
donot exite muscles and do not cause cardiac arrhythmias.
Typical effects of electrification of the human body by 50 or 60 Hz AC current.
Type of Circuit and discussions
One of the factors affecting the nature and severity of electrical injury is the type of circuit
involved, either direct current (DC) or alternating current (AC).
High-voltage DC contact tends to cause a single muscle spasm, often throwing the victim from
the source. This results in a shorter duration of exposure but increases the likelihood of traumatic

4. blunt injury.
Brief contact with a DC source can also result in disturbances in cardiac rhythm, depending on
the phase of the cardiac cycle affected, the electrophysiologic principle used with cardiac
defibrillators.
AC exposure to the same voltage tends to be three times more dangerous than DC. Continuous
muscle contraction, or tetany, can occur when the muscle fibers are stimulated at between 40 and
110 times per second.
Unfortunately, the frequency of electrical transmission used in the United States is 60 Hz, which
is near the lowest frequency at which an incandescent light will appear to be continuously lit.
The terms entry and exit are commonly used to describe electrical injuries.
The terms source contact point and ground contact point, however, are more appropriate when
referring to AC injuries.
The hand is the most common site of contact via a tool that is in contact with an AC electric
source. Since the flexors of the hand and forearm are much stronger than the extensors,
contraction of the flexors at the wrist, elbow, and shoulder will occur, causing the hand grasping
the current source to pull the source even closer to the body. Currents greater than the “let-go
threshold” (6 to 9 mA) can prevent the victim from releasing the current source, which prolongs
the duration of exposure to the electrical current.