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Questions and Answers
What defines a biosignal?
What defines a biosignal?
Which of the following is NOT a classification of biosignals based on their origin?
Which of the following is NOT a classification of biosignals based on their origin?
Which statement best describes deterministic signals?
Which statement best describes deterministic signals?
What is the main purpose of noise reduction in biosignal analysis?
What is the main purpose of noise reduction in biosignal analysis?
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Which type of biosignal is defined only at discrete points in time?
Which type of biosignal is defined only at discrete points in time?
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How can biological processes that are repetitive affect the biosignals generated?
How can biological processes that are repetitive affect the biosignals generated?
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What is the term for the process of reducing a continuous signal to a discrete signal?
What is the term for the process of reducing a continuous signal to a discrete signal?
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Which aspect is not typically significant for medical decision making when analyzing biosignals?
Which aspect is not typically significant for medical decision making when analyzing biosignals?
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What method uses the difference between two input voltages to help reduce noise in recording signals?
What method uses the difference between two input voltages to help reduce noise in recording signals?
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Which method relies on the physical property of capacitance to reduce noise effects?
Which method relies on the physical property of capacitance to reduce noise effects?
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How does electrostatic shielding reduce the influence of noise?
How does electrostatic shielding reduce the influence of noise?
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Which statement accurately describes quasiperiodic signals in living organisms?
Which statement accurately describes quasiperiodic signals in living organisms?
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Which of the following is NOT a method mentioned for reducing noise in recording systems?
Which of the following is NOT a method mentioned for reducing noise in recording systems?
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What characterizes random signals in biological processes?
What characterizes random signals in biological processes?
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In the context of noise reduction, what is the role of the differential amplifier when noise sources are distant?
In the context of noise reduction, what is the role of the differential amplifier when noise sources are distant?
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What aspect of the Earth's capacitance is leveraged in grounding to combat noise interference?
What aspect of the Earth's capacitance is leveraged in grounding to combat noise interference?
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Which of the following is a defining characteristic of a stationary signal?
Which of the following is a defining characteristic of a stationary signal?
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Which of the following statements is true about grounded systems in noise reduction?
Which of the following statements is true about grounded systems in noise reduction?
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How can signals be mathematically expressed?
How can signals be mathematically expressed?
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Which statement regarding biosignals is correct?
Which statement regarding biosignals is correct?
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What is a key feature of a conductor or mesh used in electrostatic shielding?
What is a key feature of a conductor or mesh used in electrostatic shielding?
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What are the three parameters needed to fully describe a sine wave signal?
What are the three parameters needed to fully describe a sine wave signal?
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Which biosignal reflects the electrical activity of neurons?
Which biosignal reflects the electrical activity of neurons?
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What differentiates transient signals from quasiperiodic signals?
What differentiates transient signals from quasiperiodic signals?
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What is the range of frequencies for blood pressure curves?
What is the range of frequencies for blood pressure curves?
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Which of the following describes the role of sensors in biosignal acquisition?
Which of the following describes the role of sensors in biosignal acquisition?
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Which type of sensor is designed to generate electric current directly?
Which type of sensor is designed to generate electric current directly?
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What is one characteristic of microelectrodes used in biomedical applications?
What is one characteristic of microelectrodes used in biomedical applications?
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What is the primary function of electrodes in biosignal detection?
What is the primary function of electrodes in biosignal detection?
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Which characteristic best defines passive sensors?
Which characteristic best defines passive sensors?
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What are signals that interfere with your biosignal of interest called?
What are signals that interfere with your biosignal of interest called?
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Which statement is true regarding the function of electronic signal processing in biosignal acquisition?
Which statement is true regarding the function of electronic signal processing in biosignal acquisition?
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Study Notes
Biosignals
- Biosignals are descriptions of physiological phenomena.
- Biosignals can be electric, mechanical, or chemical.
- Continuous biosignals are defined at any moment in time, while discrete signals are only defined at discrete points in time.
- Deterministic signals can be described by explicit mathematical relationships, while random signals cannot be exactly expressed.
- Repetitive biosignals may have a more or less deterministic waveform.
- Nonperiodic signals can be quasiperiodic or transient.
- Random signals are generated by random processes.
- Stationary signals have properties that do not change over time, while nonstationary signals have properties that change over time.
- Biosignals are usually functions of time, expressed as s(t), where 's' is the signal and 't' is time.
- Some signals can be described by a few parameters only.
- Complex biosignals could be a composition of several signals with different amplitudes and frequencies.
- The frequency spectrum of a signal is the collection of its frequencies and corresponding amplitudes or magnitudes.
Examples of Biosignals
- Electroencephalogram (EEG) reflects electrical activity of neurons.
- Amplitudes less than 0.1mV
- Frequency spectrum 3-200 Hz
- Electrocardiogram (ECG) reflects electric activity of the heart.
- Amplitudes less than 5mV
- Frequency spectrum 0.3-200 Hz
- Blood pressure curves are low-frequency biosignals of mechanical origin.
- Phonocardiogram (PCG) represents heart sounds.
- Biosignal of mechanical origin
- Frequency range 30-2000Hz
Biosignal Acquisition
- A sensor detects and converts biosignals to electrical signals.
- Sensors can be active or passive.
- Active sensors convert energy to electric power.
- Passive sensors detect biosignals directly or indirectly.
- Electrodes are a type of direct sensor used for detecting electric currents or voltages.
- Types of electrodes include:
- Microelectrodes: Small wires inserted into electrolyte-filled glass pipettes, used for recording potential inside a single cell.
- Small wire electrodes: Record potentials from many cells (around 100 from cardiac tissue).
- Large metal electrodes: Used for ECG recordings.
Noise during Biosignal Recordings
- Signals other than the signal of interest are called noise.
- Noise originates from internal and external sources.
- Noise reduction methods include:
- Differential amplifier: An electronic device with two inputs and one output, that amplifies the difference between input voltages to reduce noise from distant sources.
- Grounding: Connecting the recording object to the Earth to reduce noise from external electric fields.
- Electrostatic shield: Using a conductor to surround the recording space to reduce noise.
- Filtering: Removing unwanted frequency components from the signal.
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Description
Test your understanding of biosignals, including their types, properties, and distinctions between various signal categories. This quiz covers the fundamental concepts related to electric, mechanical, and chemical biosignals, as well as their classification based on determinism and periodicity. Explore how these signals are represented mathematically and their significance in physiological phenomena.