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Questions and Answers
Which materials are typically considered good conductors of electricity?
What is the unit of electrical current defined as movement of 6.25 x 1018 electrons per second?
According to Ohm's Law, how is current intensity related to voltage and resistance?
Which factor does NOT affect electrical resistance?
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What happens to skin resistance as its temperature increases?
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Which of the following is NOT a method to minimize impedance?
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Which tissues are considered poor conductors due to low water content?
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When is resistance likely to decrease?
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What is the primary aim of electrical stimulation in muscle therapy?
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Which statement accurately defines electric stimulation (ES)?
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What must be present for electrical current to flow?
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What does the net movement of electrons create?
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Which of the following describes electrical potentials?
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What is essential for creating an electrical field in biological tissues?
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How does electricity primarily arise in materials?
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Which condition is NOT required for a current to flow?
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What does the horizontal axis X represent in electrical stimulation parameters?
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What is meant by 'Isoelectric zero'?
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Which statement is true about Direct Current (DC)?
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How does Alternating Current (AC) prevent skin irritation?
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What does waveform represent in electrical stimulation?
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Which characteristic is NOT associated with Direct Current?
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What benefits does AC provide over DC in terms of skin contact?
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Which parameter does NOT describe waveform characteristics?
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What is the phase called when the membrane potential becomes more negative than the resting state?
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During which period can a neuron not fire another action potential?
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How is pulse duration typically expressed?
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Which frequency range is classified as low frequency currents?
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What effect do high frequency currents primarily produce?
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What is the main characteristic of the pulse period?
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What type of effects do medium frequency currents primarily produce?
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Which of the following examples represents a high-frequency current?
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What effect does increasing pulse duration have on nerve fiber diameter?
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Which of the following accurately describes the rate of rise in amplitude?
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What is the primary reason for the accommodation phenomenon in nerve fibers?
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Which ion is predominant inside a resting neuron?
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What is the consequence of a higher peak amplitude in stimulation?
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What triggers the depolarization phase in a neuron?
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Which of the following best describes the falling phase of an action potential?
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What does the all-or-none rule state in relation to action potentials?
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Study Notes
Electric Stimulation in Physical Therapy
- Electric Stimulation (ES) is the application of therapeutic electrical currents to excitable tissues. ES aims to generate muscle contraction, stimulate sensory nerves for pain control, and create electrical fields for injury healing.
- Basic Physics of Electrotherapy: All matter contains atoms with charged particles called ions. The net movement of electrons constitutes an electrical current.
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Electrical Potentials: A difference in electrical potential creates an electrical current.
- A battery has a higher potential at one terminal compared to the other, resulting in a flow of charges from the higher to lower potential.
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Current Flow requires a source of energy and a conducting pathway.
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Conductors offer little resistance to current flow.
- Metals like copper, gold, and silver, along with electrolyte solutions, have free electrons and facilitate conductivity.
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Insulators resist current flow.
- Air, wood, and glass have fewer free electrons and limit conductivity.
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Conductors offer little resistance to current flow.
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Current Intensity (Ampere, mA, µA): Measures the movement of electrons per second.
- 1 Ampere = 1 Coulomb per second.
- 1 milliampere (mA) = 1/1000th of an Ampere.
- 1 microampere (µA) = 1/1,000,000th of an Ampere.
- Ohm's Law: Relates current, voltage, and resistance. Current intensity is directly proportional to voltage and inversely proportional to resistance.
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Factors Affecting Resistance:
- Material Composition: High water content reduces impedance and improves conductivity (e.g., nerve and muscle). Bone, fat, tendons, and fascia have lower water content and act as insulators.
- Body Temperature: Increased temperature promotes conductivity by increasing surface salt content and moisture.
- Injury and Disease: Resistance decreases in open wounds and abrasions.
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Minimizing Impedance:
- Cleaning the skin with alcohol removes dirt and body oils.
- Removing excess hair reduces impedance.
- Warming the area before stimulation increases conductivity.
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Electrical Current Parameters:
- Horizontal Axis (X): Represents time or duration (millisecond-microsecond).
- Vertical Axis (Y): Represents magnitude or intensity (milliampere-microampere).
- Isoelectric Zero: Demarcation between positive and negative charge, where no net charge exists.
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Waveform: Visual representation of the current pulse.
- Shape, Amplitude (strength), and Duration (length of time) are key characteristics of the waveform.
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Current Direction (Polarity):
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Direct Current (DC): Constant direction, positive or negative, monopolar.
- Can cause electrolysis (breakdown of water molecules) due to constant polarity.
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Alternating Current (AC): Rapidly changes direction, positive and negative, multidirectional.
- Minimizes risk of electrolysis and chemical reactions due to rapid switching.
- Reduces skin impedance, improving tissue stimulation efficiency.
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Direct Current (DC): Constant direction, positive or negative, monopolar.
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Current Intensity and Nerve Fiber Diameter:
- Lower Intensity: Stimulates thicker, large-diameter nerves (e.g., motor nerves).
- Higher Intensity: Stimulates thinner, small-diameter nerves (e.g., sensory nerves).
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Pulse Duration and Nerve Fiber Diameter:
- Longer Pulse Duration: Stimulates thicker fibers.
- Shorter Pulse Duration: Stimulates thinner fibers.
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Amplitude (Peak Amplitude): Refers to the depth of current penetration.
- High peak amplitude penetrates deeper into the tissues.
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Rate of Rise and Decay of Pulse:
- Rise Time: How quickly the pulse reaches its maximum amplitude in each phase.
- Decay Time: How quickly the pulse returns to baseline from its peak.
- Faster rise time promotes excitability in nervous tissue due to the "accommodation phenomenon" (nerve fibers becoming less responsive to sustained stimulation).
Electrotherapy Waveform Parameters
- Direction/Polarity: Positive or negative.
- Shape: Rectangular, triangular, sinusoidal, etc.
- Duration: Time the current flows in one cycle.
- Intensity: Magnitude or strength of the current.
- Frequency: Number of pulses delivered per second (Hz).
- Burst Frequency: Number of bursts delivered per second.
Types of Electrical Currents
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Low Frequency (1-1000 Hz):
- Stimulates both sensory and motor nerves.
- Examples: Faradic current, Diadynamic current, High Voltage Pulsed Stimulation (HVPS), Transcutaneous Electrical Nerve Stimulation (TENS), Microcurrent.
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Medium Frequency (1000-10,000 Hz):
- Primarily stimulates sensory and motor nerves through modulation.
- Examples: Interferential currents, Russian currents.
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High Frequency (>10,000 Hz):
- Does not stimulate sensory or motor nerves.
- Primarily produces thermal effects.
- Examples: Shortwave diathermy, microwave, ultrasound.
Key Considerations for Stimulation
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Action Potential: The mechanism by which electrical stimulation triggers nerve and muscle responses.
- Involves changes in membrane potential due to movement of ions (sodium and potassium).
- Pulse Duration: Length of time the current flows in one cycle.
- Frequency: Number of pulses delivered per second.
- Burst Frequency: Number of bursts delivered per second.
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Description
This quiz covers the fundamentals of electric stimulation in physical therapy, focusing on the application of therapeutic electrical currents and the physics behind electrotherapy. Understand the role of electrical potentials, current flow, and the materials that facilitate or resist this flow. Test your knowledge about how electric stimulation can help in therapeutic settings.
