Timing of The Human Heart

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Summary:

How does the human heart work:
A question about the timing of the 4 chambers.

Main Question or Discussion Point

Greetings
I am a high school science teacher and music teacher. I am finishing a unit for high school biology and 5th grade science about the human body systems. I have a question about the heart. It involves timing.

I heard that the sound of the heart comes from the closing of the valves. Smaller bum for atrium valves, louder dum for vertical valves. But there are two main sounds, loud soft, loud soft. Does this mean the atrium and ventricle valves open and shut at same time for both sides of the heart?

Following is how I imagine the timing of the heart. Is this correct? (RA= right atrium, LA= left atrium, RV= right ventricle, LV= left ventricle.)
Step one- RA opens, RV closes, LA closes, LV opens.
Step two- RA closes, RV opens, LA opens, LV closes.
Back and forth. Is this correct?
Thank You!!
Steven Faivus
 

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  • #2
phyzguy
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This is not correct. The softer sound is the two atria pumping, and the louder sound is the two ventricles pumping. The two atrial valves open at the same time. Here's a video from the American Heart Association.
 
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  • #3
pinball1970
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Summary:: How does the human heart work:
A question about the timing of the 4 chambers.

Greetings
I am a high school science teacher and music teacher. I am finishing a unit for high school biology and 5th grade science about the human body systems. I have a question about the heart. It involves timing.

I heard that the sound of the heart comes from the closing of the valves. Smaller bum for atrium valves, louder dum for vertical valves. But there are two main sounds, loud soft, loud soft. Does this mean the atrium and ventricle valves open and shut at same time for both sides of the heart?

Following is how I imagine the timing of the heart. Is this correct? (RA= right atrium, LA= left atrium, RV= right ventricle, LV= left ventricle.)
Step one- RA opens, RV closes, LA closes, LV opens.
Step two- RA closes, RV opens, LA opens, LV closes.
Back and forth. Is this correct?
Thank You!!
Steven Faivus
Just to add if you can hear sounds relating to valves this can be indicative of disease. 'leaky' opening and closing resulting in back flow and turbulence. Some are harmless and common in children. Goggle heart murmurs.
 
  • #4
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This is not correct. The softer sound is the two atria pumping, and the louder sound is the two ventricles pumping. The two atrial valves open at the same time. Here's a video from the American Heart Association.
Thank you for that! I watched the video from the AHA several times. Although it did not directly address my question about the timing between the four chambers, I inferred the following.

From the animation and sound at :11- :15, it looks like both sides contract and expand in unison. The expansion ends with the softer sound production. The contractions ends with the louder sound production. It appears that in the expansion, the two atria contract, pumping their blood to the ventricles, which expand. At the end of this general heart expansion, the two valves between the atria and ventricles shut, producing the heart's softer sound. Then the heart contracts. During this part of the cycle, the two atria expand, pulling in blood from the lungs and body, and the two ventricles close, pumping blood out to the lungs and body. At the end of this part of the cycle, the ventricle valves shut, making the louder heart sound.

By my symbols the cycle would go:
1) RA closes, RV opens, LA closes, LV opens
2) RA opens, RV closes, LA opens, LA closes

Is this correct?
In a related note, I used to tell students the loud soft from the heart was from left right, as the left side is bigger and makes a louder sound. I guess I was wrong. But in the video, the right side looks bigger. The left is bigger and stronger because it pumps to the whole body, while the right pumps to the nearby lungs. Am I correct? Is the left side bigger? Does is make a louder, lower pitched sound? Why do we hear two beats and not four?
 
  • #5
phyzguy
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Thank you for that! I watched the video from the AHA several times. Although it did not directly address my question about the timing between the four chambers, I inferred the following.

From the animation and sound at :11- :15, it looks like both sides contract and expand in unison. The expansion ends with the softer sound production. The contractions ends with the louder sound production. It appears that in the expansion, the two atria contract, pumping their blood to the ventricles, which expand. At the end of this general heart expansion, the two valves between the atria and ventricles shut, producing the heart's softer sound. Then the heart contracts. During this part of the cycle, the two atria expand, pulling in blood from the lungs and body, and the two ventricles close, pumping blood out to the lungs and body. At the end of this part of the cycle, the ventricle valves shut, making the louder heart sound.

By my symbols the cycle would go:
1) RA closes, RV opens, LA closes, LV opens
2) RA opens, RV closes, LA opens, LA closes

Is this correct?
In a related note, I used to tell students the loud soft from the heart was from left right, as the left side is bigger and makes a louder sound. I guess I was wrong. But in the video, the right side looks bigger. The left is bigger and stronger because it pumps to the whole body, while the right pumps to the nearby lungs. Am I correct? Is the left side bigger? Does is make a louder, lower pitched sound? Why do we hear two beats and not four?
Yes, the left ventricle is bigger for the reason you state. The softer beat is for the atria (both atria pump at the same time), and the louder beat is for the ventricles (both ventricles pump at the same time). As @pinball1970 said, I don't think you are hearing the valves, you are hearing the contractions.
 
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  • #6
BillTre
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the two atria expand, pulling in blood from the lungs and body
A correction here.
The atria expand passively as blood flows into them from the veins. All muscles lengthen (or expand in the case of the heart muscles) passively, usually due the powered contraction of an opposing muscle, but in this case from the in-flowing blood.

The power in the cardiovascular system comes from the heart pumping blood out.
Body movements, gravity, and contraction of skeletal muscle (by squeezing on veins in different areas of the body) can power the return of blood to the heart.
 
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  • #7
berkeman
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Summary:: How does the human heart work:
A question about the timing of the 4 chambers.

I am a high school science teacher and music teacher. I am finishing a unit for high school biology and 5th grade science about the human body systems. I have a question about the heart. It involves timing.
Good for you. Fun topic to cover for your students. Are you looking at the corresponding electrical signals at all? Maybe that's too much for your single lesson on the heart, but at least from a practical perspective, we use electrical signals (via ECG/EKG) a lot more than the heart sounds in EMS.

Do you plan a lab where students can use stethoscopes to listen to heart sounds? I guess it would have to be after the shelter-in-place orders are lifted and you are back in session next school year, and you should of course clean the shared stethoscope between users.

https://en.wikipedia.org/wiki/Electrocardiography
 
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Thank you for the suggestions about including the EKG as another big indication of the heart's activity besides sound!

The main point of this model and unit is to explore how the circulatory, respiratory and digestive systems work together to serve every cell. It is an overview model leading to studying the systems and organs in more detail. The model also shows a map of how a red blood cell moves through the body. All of this gets very confusing with words but a lot more clear with a creative, well-researched interactive model.

To get back to the question, is it true to say that as the heart beats, the upper part with the atria contracts as the lower part with the ventricles expand? Then the upper atria expand and the lower ventricles contract? Do you agree the sound comes from the ventricles and atria hitting their surroundings as they pump, or is the noise from the valves?
 
  • #9
berkeman
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To get back to the question, is it true to say that as the heart beats, the upper part with the atria contracts as the lower part with the ventricles expand? Then the upper atria expand and the lower ventricles contract? Do you agree the sound comes from the ventricles and atria hitting their surroundings as they pump, or is the noise from the valves?
Do you have a stethoscope yet? It would help a lot for you to listen to your own heart or your partner's heart. That will make this much more real and understandable for you. You don't need an expensive stethoscope to hear basic heart/lung sounds.

The heart sounds that I listen to on my patients (Pts) are mostly heart pump sounds, not valve sounds. But to be honest, I only listen to heart sounds if I'm having trouble palpating (feeling) a pulse on my Pt. That happens when they are more obese or have other issues with their radial artery anatomy with respect to their distal arm structure (buried artery).

There are lots of EMS training websites for heart and lung sounds that you can listen to -- try doing a web search to find some of those audio recordings.

The normal heart contraction sequence is guided/triggered by the SA node at the top of the heart, which puts out a pacing trigger signal about once per second to the rest of the nerves that lead down the body of the heart. The atria are the first muscles to repond to that stimulus that is descending the heart, and the ventricles are the second set of muscles to respond to that descending nerve stimulus.

In a healthy heart, all of that works well. I mostly deal with hearts that are no longer healthy, and have one of several impairments that lead to loss of heart function (cardiac arrest).
 
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thank you for your comment. yes, I have stethoscopes and have also successfully used cups against students backs. I found a good video which explains what you are saying about how the heart works with the electricity and how the EKG signal creates the cycle. Thank you!
 
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