Biomedical Instrumentation Questions and Answers for Entrance exams on “Measurement of Respiration Rate”.
1. Which of the following instrument is used for recording the electrical activity of the muscles?
a) ECG
b) EMG
c) PCG
d) EEG
Answer: b
Clarification: Electromyograph is an instrument used for recording the electrical activity of the muscles to determine whether the muscle is contracting or not; or for displaying on the CRO and loudspeaker the action potentials spontaneously present in a muscle or those induced by voluntary contractions as a means of detecting the nature and location of motor unit lesions; or for recording the electrical activity evoked in a muscle by the stimulation of its nerve.
2. EMG is recorded by using surface electrodes.
a) True
b) False
Answer: a
Clarification: EMG is usually recorded by using surface electrodes because the surface electrodes may be disposable, adhesive types or the ones which can be used repeatedly.
3. Whose measurements are important for myoelectric control of prosthetic devices?
a) VCG
b) ECG
c) EEG
d) EMG
Answer: d
Clarification: EMG measurements are also important for the myoelectric control of prosthetic devices (artificial limbs). This use involves picking up EMG signals from the muscles at the terminated nerve endings of the remaining limb and using the signals to activate a mechanical arm. This is the most demanding requirement from an EMG since it depends on the working of the prosthetic device.
4. What is used to display EMG waveforms?
a) Cathode Ray Oscilloscope
b) Analog storage Oscilloscope
c) Digital Oscilloscope
d) Dual-beam Oscilloscope
Answer: a
Clarification: The Cathode Ray oscilloscope displays EMG waveforms. Electromyograph is an instrument used for recording the electrical activity of the muscles to determine whether the muscle is contracting or not; or for displaying on the CRO.
5. The amplitude of EMG signals depend upon which of the following factor?
a) Respiration
b) Position of electrode
c) Blood Resistivity
d) Ventricular Volume
Answer: b
Clarification: The amplitude of the EMG signals depends upon various factors, e.g. the type and placement of electrodes used and the degree of muscular exertions. The needle electrode in contact with a single muscle fibre will pick up spike type voltages whereas a surface electrode picks up many overlapping spikes and therefore produces an average voltage effect.
6. What is the typical range of EMG signals?
a) 0.025 to 0.050 mV
b) 0.050 to 0.1 mV
c) 0.1 to 0.5 mV
d) 0.5 to 1 mV
Answer: c
Clarification: A typical EMG signal ranges from 0.1 to 0.5 mV. They may contain frequency components extending up to 10 kHz.Such high frequency signals cannot be recorded on the conventional pen recorders and therefore, they are usually displayed on the CRT screen.
7. EMG instrument contain frequency component extending up to ____________ Khz.
a) 1
b) 5
c) 10
d) 15
Answer: c
Clarification: A typical EMG signal ranges from 0.1 to 0.5 mV. They may contain frequency components extending up to 10 kHz.Such high frequency signals cannot be recorded on the conventional pen recorders and therefore, they are usually displayed on the CRT screen.
8. What is included in the system to facilitate playback and study of EMG sound waveforms at a later convenient time?
a) Preamplifier
b) Oscilloscope
c) Tape Recorder
d) Ground Electrode