12 Questions
Which heart sound is rarely heard in normal adults, especially when the ventricle is stiff or atrial pressure is high?
Fourth sound
What is the main cause of the second heart sound?
Vibrations associated with closure of aortic and pulmonary valves
What is the frequency range of the first heart sound?
25-45 Hz
In which phase of the cardiac cycle is the third heart sound typically heard?
Diastole
Where is the best location to hear the third heart sound in most individuals?
5th intercostal space
What causes reduplication (physiologic splitting) of the second heart sound?
Frequent aortic and pulmonary valve closure during expiration
Why does the A-V bundle myofibrils have a slow rate of conduction compared to the atrial and ventricular muscles?
Due to their small size and decreased number of gap junctions
Why is the opening of the heart valves not audible when listening with a stethoscope?
Because the process of valve opening is slow and noiseless
What causes the first heart sound (S1) to be low in pitch and relatively long-lasting?
Closure of the A-V valves when the ventricles contract
What contributes to the rapid snap sound heard when the aortic and pulmonary valves close at the end of systole?
Rapid closure of the aortic and pulmonary valves
What role do gap junctions play in the conduction of the cardiac action potential?
Facilitate rapid conduction between muscle cells
Why does one not hear the opening of heart valves even though they are moving?
The opening process is silent and slow
Learn about the different rates of conduction in the cardiac action potential, including the rapid conduction in atrial and ventricular muscles, and slower conduction in the A-V bundle myofibrils. Understand how gap junctions play a role in the conduction speed.
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