29 Questions
What is the main cause of heart sounds?
Vibrations created by closure of the heart valves
What is the phonocardiograph used for?
To record the sounds connected with the pumping action of the heart
What is the purpose of phonocardiography?
To graphically record heart sounds or murmurs
What is a phonocardiogram?
A high-fidelity recording representing the rhythmicity and heart rate
Why is phonocardiography used instead of electronic stethoscopes?
Because it can detect both heart sounds that are too low in intensity and too high in frequency
What is the advantage of phonocardiographs over electronic stethoscopes?
They provide a recording of the waveforms of the heart sounds
What can even subtle changes in breath sounds be detected with?
An electronic stethoscope
What can be impaired in the absence of an airtight seal between stethoscope and skin?
Physiologic sound transmission
What is not a capability of electronic stethoscopes?
Generating constructive interference of physiologic sound waves
What determines the quality of sound wave transmission?
The airtight seal between stethoscope and skin
What is the result of the mechanical working processes of the heart?
Production of sound indicating health status
According to the valvular theory, where do heart sounds emanate from?
Point sources located near the valves
What occurs during atrial systole in the late diastolic filling period?
Blood is forced into the ventricles
What is the characteristic of innocent murmurs?
They are present in normal hearts without any heart disease
What is the cause of pathologic murmurs?
Narrowing or leaking of valves
What is necessary for heart murmurs to occur?
Blood flow above the Reynolds number
How are heart murmurs graded?
By their intensity from I to VI
What is characteristic of a Grade I murmur?
It is faint and heard only with special effort
What is a common factor involved in the production of murmurs?
Decreased viscosity
What is the primary function of the filter in the instrumentation of murmurs?
To permit selection of suitable frequency bands
What type of microphone is often used in the instrumentation of murmurs?
Crystal microphone
What is the typical bandwidth of the filter used in the instrumentation of murmurs?
20-2000Hz
What is the purpose of the integrator in the instrumentation of murmurs?
To record the envelope of higher frequency signals
Why is Rochelle salt commonly used in microphones?
It has the largest voltage output for a given mechanical stress.
What happens when mechanical stress is placed on the crystal material in a microphone?
A voltage electromagnetic force is generated.
Why is the sound pressure in the air chamber kept constant?
To keep a flat response in the pass band.
What is a characteristic of dynamic microphones?
They consist of a moving coil with a fixed magnetic core.
Why is heart sound recording with a microphone valid for a particular frequency only?
Because the microphone does not transform acoustic oscillations into electrical potentials uniformly for all frequencies.
How is the sound wave coupled to the crystal in some microphones?
Indirectly, through a diaphragm mechanically linked to the crystal.
Learn about the mechanical activities of the heart during each cardiac cycle, including the production of heart sounds, factors involved, and the role of heart valves in their production. Understand the two main heart sounds and their relationship to systole and valve closure.
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