Questions: Question 2 of 5 The nurse is auscultating an apical pulse on a 39 -year-old client admitted with pneumonia. In counting the apical pulse, the nurse recognizes which characteristic about heart sounds? Each lub-dub is one beat. Heart sounds are caused by the opening of heart valves. Each lub-dub is two beats. The lub-dub sounds occur within 2 seconds of each other. SUBMIT ANSWER

The answer is the first one: Each lub-dub is one beat.

Explanation for each option:

1. Each lub-dub is one beat.

   • Correct. The "lub-dub" sounds heard during auscultation represent one complete heartbeat. The "lub" (S1) is the sound of the mitral and tricuspid valves closing, and the "dub" (S2) is the sound of the aortic and pulmonic valves closing.

2. Heart sounds are caused by the opening of heart valves.

   • Incorrect. Heart sounds are primarily caused by the closing of the heart valves, not their opening. The "lub" sound is due to the closure of the atrioventricular valves (mitral and tricuspid), and the "dub" sound is due to the closure of the semilunar valves (aortic and pulmonic).

3. Each lub-dub is two beats.

   • Incorrect. Each "lub-dub" represents one complete cardiac cycle or heartbeat, not two.

4. The lub-dub sounds occur within 2 seconds of each other.

   • Incorrect. The timing of the "lub-dub" sounds depends on the heart rate. At a normal heart rate, the sounds occur much more frequently than every 2 seconds. For example, at a heart rate of 60 beats per minute, each "lub-dub" would occur approximately every second.

Summary: The correct answer is that each "lub-dub" is one beat, as it represents one complete cardiac cycle.