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Questions and Answers
Which of the following is NOT a type of bioelectric signal commonly monitored?
Which of the following is NOT a type of bioelectric signal commonly monitored?
Which bioelectric signal monitoring technique is primarily used to assess the electrical activity of the brain?
Which bioelectric signal monitoring technique is primarily used to assess the electrical activity of the brain?
Which monitoring technique is used to assess the electrical activity of skeletal muscles?
Which monitoring technique is used to assess the electrical activity of skeletal muscles?
Which of the following bioelectric signals is primarily used for monitoring the electrical activity of the heart?
Which of the following bioelectric signals is primarily used for monitoring the electrical activity of the heart?
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Which bioelectric signal monitoring technique is used to assess the electrical activity of the eyes?
Which bioelectric signal monitoring technique is used to assess the electrical activity of the eyes?
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What is the primary function of motor neurons in the process of muscle contraction?
What is the primary function of motor neurons in the process of muscle contraction?
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Which type of EMG electrode is most suitable for capturing the electrical activity of individual muscle fibers?
Which type of EMG electrode is most suitable for capturing the electrical activity of individual muscle fibers?
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What is the significance of the neuromuscular junction in muscle contraction?
What is the significance of the neuromuscular junction in muscle contraction?
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What is the relationship between motor units and muscle fibers?
What is the relationship between motor units and muscle fibers?
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Which of the following factors LEAST directly influences the amplitude of an EMG signal?
Which of the following factors LEAST directly influences the amplitude of an EMG signal?
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Why is surface EMG recording considered non-invasive and safe for patients?
Why is surface EMG recording considered non-invasive and safe for patients?
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What is the significance of the combined waveform of many individual motor unit action potentials (MUAPs) recorded in an electromyogram (EMG)?
What is the significance of the combined waveform of many individual motor unit action potentials (MUAPs) recorded in an electromyogram (EMG)?
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What is the primary advantage of using a needle electrode for EMG recording?
What is the primary advantage of using a needle electrode for EMG recording?
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Which of the following statements accurately describes the relationship between the EMG signal and the force generated by a muscle?
Which of the following statements accurately describes the relationship between the EMG signal and the force generated by a muscle?
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A surface EMG electrode, compared to a needle electrode, typically captures a signal from a larger area of muscle tissue. What is the primary consequence of this difference?
A surface EMG electrode, compared to a needle electrode, typically captures a signal from a larger area of muscle tissue. What is the primary consequence of this difference?
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Flashcards
ECG
ECG
A test that measures the electrical activity of the heart.
EMG
EMG
A test that measures the electrical activity of muscles.
EEG
EEG
A test that records electrical activity in the brain.
Bioelectric Signals
Bioelectric Signals
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Monitoring
Monitoring
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Motor Unit
Motor Unit
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Motor Neurons
Motor Neurons
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Neuromuscular Junction
Neuromuscular Junction
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Action Potentials
Action Potentials
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Electromyogram (EMG)
Electromyogram (EMG)
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Factors affecting EMG amplitude
Factors affecting EMG amplitude
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Surface Electrode
Surface Electrode
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Needle Electrode
Needle Electrode
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Electromyography
Electromyography
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Study Notes
Chapter 2 - Bioelectric Signals Monitoring
- Learning Objectives: ECG, EMG, EEG, Sleep Study
Electrical Activities in the Muscles
- Motor Unit: Muscle Fibers + Neuromuscular Junctions + Motor Neurons
- EMG Recording: Combined waveform of many individual signals from each motor unit
- Individual signal trains from each individual motor unit (MUAP)
Electromyogram (EMG)
- Definition: Graphical recording of electrical activity in skeletal muscle.
- Muscle Activity at Rest: Little to no electrical activity.
- Muscle Flexion: Causes some electrical activity. Stronger contraction leads to more activity.
- Muscle Response: Pattern helps doctors determine if the muscle is responding correctly.
- Needle Insertion: Causes electrical activity, but this subsides after initial insertion.
- Raw EMG Signal: The difference in electrical potential measured between two recording electrodes. The signal's origins include electrical activity from various tissues.
- Motor Neuron Action Potential: Causes an end plate potential in motor units of muscle fibers.
- Muscle Membrane Depolarization: Directly depolarizes muscle membrane near the muscle fiber's center.
- Depolarization Wave: Travels from muscle surface along transverse tubules into fiber's interior and along membrane's surface creating a train of bipoles.
Electrical Activities in the Muscles - EMG
- EMG characteristics: Frequency response between 20Hz and 200Hz, maximum signal amplitude of 10mV.
- Kinesiological EMG : Scientific study of movements of body parts (functional anatomy, force development, reflexes).
- Diagnostic EMG: Used for diagnoses.
Electromyography (EMG) - Diagnostic and Clinical Applications
- Nerve and Muscle Integrity Testing: Strength-duration curves.
- Differentiating Nerve and Muscle Diseases.
- Assessing Weakness and Sensory Abnormalities: Due to peripheral nerve / muscle issues.
- Nerve Compression/Injury: Nerve conduction velocity test.
- Nerve Root Injury: Detected by EMG.
- Firing Characteristics of Motor Neurons/Motor Units: Including fibrillation.
- Partial Paralysis Detection.
Electrical Activities in the Muscles - Electromyogram (EMG)
- Factors Affecting EMG Amplitude: Electrode type and placement, level of muscular exertion. Need electrodes are in contact with single muscle fiber and pick up spikes of voltages
- Surface electrode picks up many overlapping spikes, thus producing an average voltage effect.
Electromyograph
- Definition: The machine/instrument to record electrical activity in a skeletal muscle.
- Function: Detects electrical potential generated by muscle cells when activated electrically or neurologically. Components; Signal processor, ADC (analog-to-digital converter), Filtering & Conditioning , Amplifier and EMG Recording Unit
Electrodes Used in EMG
- Surface Electrodes/Ag-AgCl; Small metal disc on skin overlaying muscle (0.5-1.5 cm long). Used to record EMG superficial muscles. Surface EMG recording uses self-adhesive sensors placed on the skin to detect electrical impulses from the muscle. Noninvasive, painless, and safe.
- Hypodermic-Needle/Inserted/Concentric Electrode: Inserted into muscle; records deep muscle EMG. Needle EMG recording uses a needle electrode, directly penetrating the muscle. provides info about a single muscle fiber instead of the overall condition of the muscle.
Electromyography
- Method : Recording electrical activity in skeletal muscle. Usually involves testing and recording neuromuscular activity from electrical stimulation of nerves.
- EMG Waveform: The presence, size, and shape of the EMG waveform provides information about the muscle's response to nervous stimulation.
- High Impedance: Due to high impedance of electrode/skin or electrode/muscle interfaces, EMG amplifiers need very high input impedance for appropriate amplification of the acquired raw EMG signal from the electrodes.
Evoked EMG Measurements/ENG
- Nerve Identification: Locating the termination/distal point of the nerve under study.
- Electrode Placement: Two EMG electrodes placed at the termination point to record muscle signal.
- Stimulator Placement: Stimulator attached near the nerve's origin to send a pulse.
- Pulse and Recording: Pulse is sent. Recorded signal from the muscle's innervated by the nerve.
Time Measurement in ENG
- Normal Response Time: Normal nerves respond in less than 10 milliseconds. This result in a healthy single wave.
- Pathological Response Time: Pathological conditions cause waveforms with multiple waves and durations always greater than 10 milliseconds.
Nerve Conduction Velocity Test (NCV)
- Function: This method is used to diagnose nerve damage/destruction and diseases of nerve/muscle.
- Electrode placement: Surface electrodes at specific nerve locations are necessary.
- Stimulation: Electrical impulses from the electrodes stimulate the nerve.
- Recording: The resulting electrical activity is recorded to assess the speed of impulses travelling between electrodes to calculate nerve speed.
EMG Signal Processing
- Rectification: Negative content of the EMG is flipped to positive.
- Filtering: High pass filter to remove unnecessary electrical noise.
- Digital Smoothing: Applying algorithms to identify patterns in the EMG signal. Steep amplitude spikes are removed, thus creating a linear envelope
Signal to noise ratio
- Signal to noise ratio of acquired signal: Methods include large surface areas for detection, electrodes, using conductive electrolytes to improve contact, and removing dead dermis from skin
- Methods: Large detection surfaces, conductive electrolytes for skin contact, and removal of dead dermis.
Bandwidth
- Inter-detection Surface Spacing/Nerve Conduction: Bandwidth is affected by inter-detection surface spacing and nerve conduction velocity of action potentials along muscle fibers
- Specified Frequency: For a conduction velocity of 4 mm/ms and 1.0 cm spacing, the frequency should be 200 Hz.
- Filter Cut-off: 200 Hz filter cut-off frequency is necessary to capture the full frequency spectrum and lower noise at higher frequencies.
Muscle Sample Size
- Size Consideration: Muscle sample size doesn't need to be large, since motor units are distributed.
- Sample Representation: A smaller muscle sample with detection surface of electrodes provides a representative sample of EMG for a group of active motor units.
Cross-Talk Susceptibility
- Overlooked Issue: Cross-talk is often overlooked for detection surfaces with size and distance between the electrodes for detecting signals from adjacent muscles.
- Larger Electrodes: Increases susceptibility to signals from adjacent muscles/lower electrode sizes.
- Reduced Electrode Size: This helps prevent signal interference from adjacent muscles.
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Description
Explore the fundamental concepts of bioelectric signals in Chapter 2. This quiz covers topics such as ECG, EMG, EEG, and important sleep study techniques. Test your understanding of electomyograms and the electrical activities of muscles with a focus on motor units and their recordings.
