Biomedical Instrumentation: ECG, EEG, and EMG Basics Quiz Quiz

Explore essential concepts of biomedical instrumentation focusing on ECG, EEG, and EMG basics. This quiz covers electrode placement, physiological signals, and interpretation to help learners solidify their understanding of common biomedical devices and their applications.

1. ECG Electrode Placement

   Which standard limb lead in an electrocardiogram (ECG) records the electrical potential difference between the right arm and left arm electrodes?

   1. Lead III
   2. Lead IV
   3. Lead I
   4. Lead II

   Explanation: Lead I measures the voltage difference between the right arm and the left arm electrodes, which is essential in standard 12-lead ECG interpretation. Lead II records between the right arm and the left leg, while Lead III is between the left arm and left leg. There is no standard ‘Lead IV’ in ECG; this is a distractor.

2. EEG Brainwave Frequencies

   When recording an EEG, which frequency range most commonly corresponds to the alpha rhythm, typically observed when a person is awake but relaxed with eyes closed?

   1. 14–30 Hz
   2. 1–4 Hz
   3. 8–13 Hz
   4. 35–50 Hz

   Explanation: Alpha waves are most prominent within the 8–13 Hz range and appear during relaxed, wakeful states with closed eyes. Beta waves (14–30 Hz) occur during active thinking and alertness, delta waves (1–4 Hz) during deep sleep, and the 35–50 Hz range exceeds normal physiological brain rhythms, making these distractors incorrect.

3. EMG Signal Interpretation

   In an electromyogram (EMG), what does an increase in the amplitude of the recorded signal usually indicate about the muscle’s activity?

   1. The muscle is becoming denervated
   2. Electrode placement is incorrect
   3. A reduced muscle contraction force
   4. A greater number of motor units are active

   Explanation: A higher amplitude in EMG signals typically reflects that more motor units are being recruited or that their action potentials are summing. Denervation often leads to changes in firing patterns, not necessarily amplitude. Incorrect electrode placement may reduce the signal, and reduced contraction force would cause lower, not higher, amplitudes.

4. Biomedical Signal Artifacts

   Which of the following is a common source of artifact in EEG recordings that can mimic genuine brain activity?

   1. Pulse oximetry error
   2. Glucose level
   3. Skin impedance
   4. Eye movement

   Explanation: Eye movement, particularly blinking and rolling, produces large electrical signals that can contaminate EEG recordings and may be mistaken for brain activity. High skin impedance affects signal quality but does not mimic neural patterns. Pulse oximetry error and glucose levels do not directly affect EEG signals.

5. Signal Characteristics: ECG, EEG, vs. EMG

   Which statement best describes the frequency characteristics of EMG signals when compared to ECG and EEG signals?

   1. EMG and ECG have the same frequency range
   2. EMG signals are predominantly low-frequency like EEG delta waves
   3. EMG signals generally have higher frequency content than ECG and EEG signals
   4. EMG frequencies are similar to the alpha rhythm in EEG

   Explanation: EMG signals typically have higher frequency components, often ranging from 10 to 500 Hz, reflecting rapid muscle activity. EEG alpha rhythms are lower in frequency, and EMG is not predominantly low-frequency. The frequency ranges of EMG and ECG overlap somewhat, but EMG predominates in higher frequencies, unlike the relatively lower-frequency ECG.