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634: Electrotherapy Modalities > Basic Principles of Electricity (Part 2) > Flashcards

Basic Principles of Electricity (Part 2) Flashcards

1
Q

What are the 3 types of physiologic responses to electrical current?

A
  • Electrothermal effects
  • Electrochemical Effects
  • Electrophysical effects
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2
Q

Describe the electrothermal effect of electrical current?

A

When an electrical current is added charged particles begin to microvibrate which causes an associated frictional force which leads to the production of heat

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3
Q

Tissues of higher resistance should heat up ___ when electrical current passes through.

A

more

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4
Q

What is the thermal effect of electrical current used for stimulation of muscle and nerve?

A

These types of electrical current have low average current flow which allows for minimal thermal effects

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5
Q

Describe the electrochemical effects to electrical current

A

The unidirectional flow of DC redistributes sodium and chloride to form a new chemical compound in the tissue under the electrodes

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6
Q

Describe the migration of charged particles under the positive and negative poles and the type of reaction produced at each

A

At the positive pole negatively charged particles migrate and cause an acidic reaction.

At the negative pole positively charged particles migrate and cause an alkaline reaction

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7
Q

What is the body’s response to the acidic and alkaline reactions produced?

A

The body increases circulation in order to restore normal tissue pH

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8
Q

Practical elimination of chemical effects at the tissue level can be obtained if what type of current is used?

A

a pulsed current (PC) rather than direct current (DC) is used

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9
Q

Describe the electrophysical effects of electrical current

A

The charge developed by an electrical current in tissue causes movement of ions which can excite peripheral nerves and cause a muscle belly to jump a bit

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10
Q

The movement of sodium and potassium ions across the cell membrane may lead to what 3 different direct responses?

A
  • Contraction of skeletal or smooth muscles
  • Activation of endogenous analgesic mechanisms which reduces pain
  • Various vascular responses
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11
Q

What type of effect will occur with an electrical shock of 0-1 mA?

A

None, it is imperceptible

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12
Q

What type of effect will occur with an electrical shock of 1-15 mA?

A

Tingling sensation and muscle contraction

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13
Q

What type of effect will occur with an electrical shock of 15-100 mA?

A

Controlled muscle contraction on the low end

Painful electrical shock on the high end

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14
Q

What type of effect will occur with an electrical shock of 100-200 mA?

A

Cardiac or respiratory arrest

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15
Q

What type of effect will occur with an electrical shock greater than 200 mA?

A

Instant tissue burning and destruction

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16
Q

What are the 4 therapeutic uses of electricity?

A
  • To create muscle contraction via nerve or muscle stimulation
  • Stimulate sensory nerves to help in treating pain
  • To create an electrical field in biologic tissues to stimulate or alter the healing process
  • To create an electrical field on the skin surface to drive ions beneficial to the healing process into or through the skin
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17
Q

Electrical stimulation may alter the body’s physiology on what four levels?

A
  • Cellular
  • Tissue
  • Segmental
  • Systematic
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18
Q

How does electricity alter physiology on the cellular level?

A
  • Excitation of nerve cells
  • Changes in cell membrane permeability
  • Protein synthesis
  • Stimulation of fibroblasts and osteoblasts
  • Modification of microcirculation
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19
Q

How does electricity alter physiology on the tissue level?

A
  • Skeletal muscle contraction
  • Smooth muscle contraction
  • Tissue regeneration
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20
Q

How does electricity alter physiology on the segmental level?

A
  • Modification of joint mobility
  • Muscle pumping action to change circulation and lymphatic activity
  • Alteration of the microvascular system not associated with muscle pumping
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21
Q

How does electricity alter physiology on the systematic level?

A

They can produce analgesic effects in 2 ways:

  • as endogenous pain suppressors that are released and act at different levels to control pain
  • from the stimulation of certain neurotransmitters to control neural activity in the presence of pain stimuli
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22
Q

Physiological responses can be broken down into direct and indirect, explain the difference between the two.

A

There is always a direct effect along the lines of current flow and under the electrodes.
Indirect effects occur remote to the area of current flow and are usually the result of stimulating a natural physiologic event to occur (such as wrist extension)

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23
Q

If a certain effect is desired from stimulation, tissue response goals must be set. These response can be grouped into two basic physiological responses, what are they?

A

excitatory or non-excitatory

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24
Q

How do patients perceive excitatory responses?

A

As electric sensation, muscle contraction, and electric pain

25
Q

Excitability of nerves and muscles is dependent upon what?

A

the cell membrane’s voltage sensitive permeability

26
Q

What does the cell membrane’s voltage sensitive permeability produce?

A

An unequal distribution of charged ions on each side of the membrane which creates a potential difference between the charge of the interior and exterior of the cell. This makes the membrane polarized

27
Q

The potential difference between the inside and outside of the cell is known as what?

A

resting potential

28
Q

Is there a greater concentration of diffusible positive ions on the inside or outside of the membrane?

A

outside

29
Q

What two things maintain the larger concentration of positive ions on the inside of the cell membrane?

A
  • Continuous activity of the sodium pumps that move Na+ from inside to outside the cell
  • Voltage-activated potassium channels allow K+ to move into the cell
30
Q

Is there a higher K+ concentration inside or outside the cell?

A

inside

31
Q

The overall charge difference between the inside and outside of the cell creates an electrical gradient at its resting level of -__ mV to -__ m

A

-70 mV to -90 mV

32
Q

What two conditions are necessary for the membrane potential to develop?

A
  1. The membrane must be semipermeable

2. The concentration of the diffusible ions must be greater on one side of the membrane than on the other side

33
Q

In order to create transmission of an impulse in the nerve tissue what must occur?

A

The resting membrane potential must be reduced below a threshold level for changes in the membrane’s permeability to occur. These changes then create an action potential which propagates the impulse along the nerve in both directions from the location of the stimulus

34
Q

As the charged ions move across the nerve fiber membranes beneath the anode and cathode what occurs?

A

membrane depolarization

35
Q

Dexcribe what occurs at the cathode and anode during depolarization.

A

The cathode is usually the site of depolarization, while the anode makes the nerve cell membrane potential more positive, increasing the threshold necessary for depolarization

36
Q

What is the absolute refractory period?

A

The brief period following excitement and propagation of the impulse along the nerve fiber during which the nerve fiber is incapable of reacting to a second stimulus

37
Q

Once the neurotransmitter crosses the synapse to the muscle effector organ what happens?

A

a twitch muscle contraction results

38
Q

The ____-____ curve is a graphic representation of the threshold for depolarization of a particular nerve fiber

A

strength-duration (SD) curve

39
Q

The strength-duration curve shows the relationship between what?

A

The current intensity (strength) and current duration in causing depolarization of a nerve or muscle membrane

40
Q

_____ is term that identifies the specific intensity of current necessary to cause observable tissue excitation, given a long current duration.

A

Rheobase

41
Q

_____ identifies the specific length of time or duration required to cause observable tissue excitation, given a current intensity of two times rheobasic current

A

Chronaxie

42
Q

In reference to the strength-duration curve, what are 3 important concepts to keep in mind?

A
  1. The shape of the curve relates the intensity of the electrical stimulus and the length of time necessary to cause the tissue to depolarize
  2. The rheobase describes the minimum intensity of current necessary to cause tissue excitation when applied for a maximum duration
  3. The chronaxie describes the duration required for a current of twice the strength of the rheobase current to produce tissue excitation
43
Q

The chronaxie is always ___ as large as the rheobase.

A

twice

44
Q

Describe the concept of the all-or-none response

A

Once a stimulus reaches a depolarizing threshold it will either cause depolarization (the all) or it will not cause depolarization (the none)

45
Q

In the absence of muscle innervation, is it possible for a muscle to contract? How?

A

Yes, by using electrical current that causes the muscle membrane to depolarize (rather than the motor nerve)

46
Q

What is the purpose for electrically stimulating denervated muscle?

A

To help minimize the extent of atrophy during the time that the nerve is regenerating

47
Q

How can e-stim be used to cause pain modulation?

A

By activating either the gate control or endogenous opiate mechanisms

48
Q

____-volt currents are used for a variety of clinical purposes: to elicit muscle contraction, for pain control, and for reducing edema

A

High

49
Q

High-volt currents are characterized by a ___-rate frequency and ___ amplitude

A

high

low

50
Q

Frequencies around __ pps may be optimal for pain relief

A

60

51
Q

A ____ pulse duration seems to selectively stimulate larger diameter myelinated afferent fibers

A

short

52
Q

How does e-stim accelerate the healing process of wounds?

A

Enhancing wound circulation by promoting the growth of new blood vessels

53
Q

What type of electrical current has been shown to have a bacteriostatic action in open wounds?

A

Low intensity direct current

54
Q

What has been shown to effectively reduce post-traumatic edema?

A

Rhythmic muscle contraction, either voluntary or electrically induced

55
Q

“Low rate” stimulation may be more effective if the electrodes are placed over what?

A

Motor points since a motor response is a desired outcome

56
Q

What are the 2 types of electrodes?

A
  • Surface (transcutaneous): electrodes placed in contact with the skin
  • Invasive : electrodes that penetrate the skin
57
Q

As electrode contact area decreases, current density ______

A

increases

58
Q

Larger electrodes have ____ impedance

A

lower

634: Electrotherapy Modalities (11 decks)

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