Pressure in the left heart - part 1 | Circulatory system physiology | NCLEX-RN | Khan Academy

Watch the pressure in the left heart go up and down with every heart beat! Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.

About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.

For free. For everyone. Forever. #YouCanLearnAnything

[jborniard]

I wish this gentleman was my biology teacher. I've been struggling with this topic for months. Thank you so very much for a great teaching experience. Simple and to the point!!!!

[crock]

You are seriously my hero. The way you build intuition is amazing. Wanna do biochemistry next? 

[kokocipher]

the details made all the difference. thank you

[alighalibsheikh]

Quick question, thanks for the awesome video, aren't the AV valves slighty open as blood leaks into the ventricles as pressure increases in ventricles?

[gilllie]

I was taught the sounds are actually made by the turbulence in the blood after the valves shut. IE the valves shut quietly but the turbulence following cause the noises.

[jseanbrooks]

I love your videos very much, thank you for all you have done for us. If I had one tiny suggestion, I would really recommend buying a pop filter. You can get one for as little as $10, and it will noticeably improve the sound quality - very important for this style of videos. Thank you again for all of the supplemental lectures :)

[rainasajid]

Thank you so much, sir!
May Allah bless you always!

[yogeshnalam]

Hello. Can you tell me if the pressures shown when the ventricle is compressing before the aortic valve opens. Are those static pressures or they have a component of dynamic pressure? Thank you

[Anto__]

Thank you for this video but I have a question: what is the value of pression in the right atrium and in the left atrium?

[hellerebanditters]

I have a question: after the semilunar valves open as an effect of increased pressure inside the LV, the pressure from the LV and the aorta sort of matches because of resistance met from arteries connected to the aorta. I am not sure what causes this resistance? Can someone enlighten me? Is it like a basic blood pressure caused by the prior heart pressure phases?
thank you

[TehInspiration]

Correction:

The P wave is the depolarization of the atria. Due to the delay between action potential and muscle contraction, the atrial systole will not begin until the middle of the P wave. With to the AV valve being open, the blood from the atria will flow to the ventricle causing ventricular blood volume will increase till it reaches the R wave. Once the atrial systole ends at the R wave, the ventricle will have a much higher pressure (due to the increase in blood volume) which will close the AV valve (creating the first heart sound).

The Q wave marks the beginning of ventricular depolarization but the ventricular systole does not occur until the R wave due to the delay of action potential. With both valve's being closed, the ventricular systole will create even more ventricular pressure (or go through "isovolumic contraction"). This will cause the semilunar valves to open at the end of the S wave.

At the end of the S wave, the ventricle volume will significantly decrease due to the ejection of blood through the semilunar valves. With the ventricular volume/pressure decreasing and the arterial volume/pressure increasing, the semilunar valves will close to preventing the backflow of blood. The semilunar valve closes at the middle of the T wave, and it creates the second heart sound.

The T wave represents the repolarization of the ventricles. With the semilunar and AV valve closed, the atrial volume will begin to increase (or go through "isovolumic relaxation").

From here the atrial volume/pressure is higher than the ventricle pressure, causing the AV valve to open at the end of the T wave. Now that the AV valve is open, blood will begin to start flowing back into the heart passively. This marks the beginning of ventricular diastole. The ventricular pressure will slightly increase until the middle of the next P wave where the cycle repeats.

[Feel free to reply to this comment if I made any mistakes]

[KRon]

What engineered natural selection? The designer

[ericlucking]

Hi everyone! Does anybody know what software is used to record active drawing like this? It looks amazing!

[annellemorgan]

Okay. Non medical here. I have 23 mmHg LVDEP. What if anything can I do to lessen the pressure besides taking spironolactone. Or is my expiration date closer than I thought.

[catchme]

Hi! I didn't pass the physiology exam last time because I was asked about the isovolumic relaxation and the professor wanted to know why, despite the pressure falls, the volume doesn't change. I tried to tell her the obvious things (that the valves are both closed) but she started talking about the Laplace law and I didn't understand. Could you explain this to me?

[qubach]

Engineering would imply a designer my friend. The only engineer here is natural selection!

[elaineluther]

I found it very confusing that you kept referring to the aortic valve as the semilunar valve. This made the video hard to follow, and inaccurate, because you weren't talking about BOTH the pulmonic and aortic valves, which are the semilunar valves.

Similarly, it was confusing that you kept referring to the mitral valve as the AV atrio-ventricular valve. AV valve actually would mean BOTH the tricuspid and mitral valves, and you were only talking about the mitral valve.

Would you consider re-recording the audio to make the video more accurate and easier to follow?