Electrical Stimulation Principles & Physiology

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Questions and Answers

Which type of electrical stimulation is primarily used for pain management?

  • NMES
  • FES
  • Iontophoresis
  • TENS (correct)

Iontophoresis is used for stimulating muscle contractions.

False (B)

What does NMES stand for?

Neuromuscular Electrical Stimulation

The type of electrical stimulation used for wound healing is _______.

<p>high volt</p> Signup and view all the answers

What is the primary function of FES?

<p>Orthotic substitute (B)</p> Signup and view all the answers

C fibers are responsible for sensory perception.

<p>False (B)</p> Signup and view all the answers

What is the all-or-none principle in relation to muscle fibers?

<p>It states that a muscle fiber will either respond fully or not at all when stimulated.</p> Signup and view all the answers

To achieve muscle contraction in a denervated muscle, _______ is required.

<p>direct current</p> Signup and view all the answers

Match the following types of electrical stimulation to their primary use:

<p>TENS = Pain relief High volt = Wound healing Iontophoresis = Drug delivery NMES = Muscle re-education</p> Signup and view all the answers

What factors can affect the speed of nerve conduction?

<p>Prolonged icing, pressure, anoxia/ischemia can slow nerve conduction; myelination can increase speed.</p> Signup and view all the answers

Which contraction occurs first when using electrical stimulation?

<p>Large motor units first (D)</p> Signup and view all the answers

Voluntary contractions are more fatiguing than electrically generated contractions.

<p>False (B)</p> Signup and view all the answers

What is the relationship between strength and duration in electrical stimulation?

<p>Inverse relationship</p> Signup and view all the answers

The only electrical stimulation unit capable of delivering enough charge to reach the threshold of the muscle membrane is _____ because it has a long duration.

<p>DC</p> Signup and view all the answers

Match the following responses to their descriptions:

<p>Sensory response = Buzzing tingling sensation Motor response = Weak contraction that strengthens Pain response = Discomfort felt during stimulation</p> Signup and view all the answers

What happens when the amplitude increases while duration remains constant during electrical stimulation?

<p>Motor response becomes stronger (D)</p> Signup and view all the answers

The threshold for activating sensory nerves is higher than for pain nerves.

<p>False (B)</p> Signup and view all the answers

Which type of motor unit recruitment pattern is seen during voluntary contractions?

<p>Small motor units recruited before large</p> Signup and view all the answers

Pulses with short durations require _____ amplitude to reach threshold.

<p>higher</p> Signup and view all the answers

What is the sequence of activation of nerves during electrical stimulation?

<p>Sensory - Motor - Pain (A)</p> Signup and view all the answers

Flashcards

Electrical Stimulation (E-Stim)

Using electrical currents to stimulate nerves and muscles for therapeutic purposes.

All-or-None Response

A nerve or muscle fiber either fully responds to a stimulus or doesn't, there is no partial response.

Strength-Duration Curve

A graph showing the relationship between the strength and duration of an electrical stimulus needed to elicit a response in a nerve or muscle.

Motor Point

The specific area on a muscle where electrical stimulation produces the greatest response.

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Motor Unit

A motor neuron and all the muscle fibers it controls.

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Sensory Neuron Stimulation

Electrical stimulation that activates sensory nerves.

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Denervated Muscle

A muscle that has lost its nerve supply.

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Conductors

Materials with low resistance to electrical current (e.g., nerves, muscles).

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Insulators

Materials with high resistance to electrical current (e.g., skin).

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NMES

Neuromuscular Electrical Stimulation - used to strengthen muscles, and treat edema.

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Voluntary Muscle Contraction

A smooth increase in muscle tension, achieved by recruiting small motor units first, followed by large ones, and asynchronous firing, allowing motor units to recover while others contract.

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Electrical Muscle Contraction

A quick and abrupt muscle contraction, involving the recruitment of large motor units before small ones, and synchronous firing that leads to fatigue as all motor units fire in unison.

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Motor Unit Recruitment

The process of activating additional motor units to produce greater force during muscle contraction, either voluntarily or electrically.

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Asynchronous Firing

Sequential activation of motor units to allow for recovery and prevent fatigue during voluntary muscle contractions.

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Synchronous Firing

Simultaneous activation of motor units that rapidly leads to muscle fatigue during electrical stimulation.

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Threshold of Nerve/Muscle

The minimum stimulus needed to trigger a response on the nerve or muscle membrane.

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Amplitude & Motor Recruitment

The amplitude of stimulation directly influences the number of motor units recruited, leading to a corresponding increase in the strength of the contraction.

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Sensory Stimulation Threshold

Sensory nerves' threshold is lower than pain nerves' threshold, requiring less stimulus for activation.

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Sensory vs. Motor response to E-stim

Sensory response starts with buzzing/tingling, Motor response starts as a weak contraction that intensifies as more motor units are recruited, pain is last.

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Study Notes

Electrical Stimulation Principles

  • Clinical Applications:
    • Pain relief (TENS, IFC)
    • Edema reduction (high volt, NMES)
    • Muscle re-education/strengthening (NMES, Russian)
    • Range of motion (ROM) improvement (NMES)
    • Wound healing (high volt)
    • Denervated muscle activation (direct current)
    • Drug delivery (iontophoresis)
    • Muscle spasm/guarding (NMES)
    • Functional electrical stimulation (FES) for orthotics (e.g., drop foot, anterior tibialis) (NMES)

Physiology of Electrical Stimulation

  • Action Potential Basics: Electrical stimulation works by creating action potentials in nerve and muscle fibers. The strength and duration of the stimulus must reach the tissue's threshold to initiate this response.

  • Stimulus Characteristics:

  • Strength: Intensity and amplitude influence the stimulus's ability to reach threshold.

  • Duration: Longer pulses generally need less intensity to reach threshold than shorter pulses.

  • Rise Time: The speed of the pulse's increase also affects its ability to excite tissue.

  • Charge: The area under the stimulus waveform. Critically important for depolarization.

  • Sensory vs. Motor Stimulation: Sensory, motor or pain stimulation of nerve stimulation depends on the type of nerve fibers activated (sensory, motor, or pain fibers).

  • Denervated Muscle Stimulation: Denervated muscles require higher stimulus intensity and longer duration (DC) due to a higher threshold compared to normally innervated muscles.

  • Conduction Speed: Factors like prolonged icing, pressure and ischemia all negatively impact nerve conduction speed. Myelin sheath promotes faster conduction through saltatory conduction.

  • Conductors and Insulators:

    • Conductors: Nerve, muscle, blood, motor points, trigger points have low electrical resistance.
    • Insulators: Skin, adipose tissue, hair, callus, scar tissue have high electrical resistance.

Motor Units

  • Motor Unit: A motor neuron and the muscle fibers it innervates.
    • Small Motor Units: Fine motor control (e.g., eye muscles, 1:5 nerve-to-muscle fiber ratio).
    • Large Motor Units: Gross motor control, force production (e.g., quadriceps muscles, 1:50 ratio).

Voluntary vs. Electrically Generated Contractions

  • Voluntary Contractions:

    • Gradual recruitment of motor units.
    • Asynchronous firing for recovery.
    • Less fatiguing.

  • Electrical Stimulation Contractions:

    • Abrupt recruitment of motor units.
    • Synchronous firing; Fatigue more quickly.
    • Amplitude directly relates to the muscle recruitment strength.

Strength-Duration Curve Interpretation

  • Inverse Relationship: Shorter pulses need higher intensity, while longer pulses need lower intensity to reach the same threshold.
  • Nerve Stimulation Sequence: Sensory → Motor → Pain (sensory threshold is lowest).
  • Amplitude Increase (Constant Duration): Higher amplitude with constant duration will progressively create a stronger contraction as more motor units are recruited.

Threshold Considerations

  • Muscle vs. Nerve Thresholds: Muscle membrane has a higher threshold for activation by electrical stimulation than nerve membranes, thus requiring differing stimulus parameters.

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