What percent of blood pass from the atria to the ventricles before the atrial walls contract?

Which part of the heart delays the electrical impulse to allow for atrial emptying of blood before ventricular contraction?

The AV node slows down the impulse giving the atria time to contract before the ventricles contract.

Do atria contract before the ventricles?

Yes, atria contracts before the ventricles.

What percentage of the blood from the atria passes into the ventricles before the atrial walls contract?

About 60-70%, but decreases in case of tachycardia, it may even reach about 50% in case of severe exercise

Which ecg wave must occur before the ventricles can relax?

The QRS complex causes the ventricles to contract. This has to happen before they can relax.

What wave must occur before the ventricles can contract?

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How much blood from the aorta passes into the ventricles before the atria contract?

lots :)

What is AV nobes?

I think you mean 'AV Node'. If so, then it is part of the hearts pace maker called the Atrio-ventricular node. It emits an electric pulse across the ventricles to make them contract (ventricular systole). This pulse would have come from the SA (Sino-atrial) node, which would have made the atria contract before the electric pulse reached the AV node.

What occurs during left ventricular relaxation?

open

What are junctional fibers?

On the Net, you can find different things being said about the cardiac "junctional fibers". I am going to offer what I understand makes the most sense. The junctional fibers are cardiac muscle cells which are specialized for slowing down the cardiac impulse just before it goes into the atrioventricular node. This delay gives the atria time to empty their blood into the ventricles before the cardiac impulse goes on to stimulate the ventricles to contract. Notes: (1) These junctional fibers are not nerve cells, but are muscle cells which are specialized for conducting the cardiac impulse. You may know how more-narrow nerve axons are slower at passing on an action potential, while wider axons can pass on an action potential faster. Well, these junctional fibers are like nerve fibers, in this way > because these junctional fibers are very narrow, they can slow down the cardiac impulse. (2) So, where do you think these narrow junctional fibers need to be, in order to slow down the cardiac impulse at the right place and time? If the cardiac impulse were to go from the atria right on to to the ventricles, then the ventricles would be stimulated to contract while the atria were still trying to empty blood into the ventricles. And so, the ventricular blood pressure would be pushing back against the blood that was trying to get from the atria into the ventricles. This would not be good. So . . . the heart needs to slow that impulse, just after it leaves the atria . . . slowing it long enough so the ventricles stay relaxed while they receive blood from the atria. (3) And, lo and behold . . . the junctional fibers are located right after the atria; and they receive the impulse which comes from the atrial muscles; then it delays the impulse before letting it go into the atrioventricular node. This slow-down gives the atrial muscles just enough time to finish contracting before the atrioventricular node sends on the cardiac impulse to stimulate the ventricles to contract. (4) You might notice on an EKG how there is the P wave showing atrial depolarization. Then the line goes flat for a little bit before the QRS complex. At the beginning of that flat time at the end of the atrial depolarization, this is where the junctional fibers are slowing down the cardiac impulse before it shows as the QRS which shows the impulse being fired by the atrioventricular node to the ventricles, I understand.

How does the impulse to contract slow down slightly before it is transferred into the ventricles?

junctional fibers leading into the AV node have very small diameters

What causes the normal delay in transmission at the AV node What is the importance of this delay for cardiac function?

The delay occurs within the fibres of the AV node. It is important because it allows the atria to complete their contraction and empty their blood into the ventricles before the ventricles contract. There is a short delay (1 m/second) in transmission of the impulse to the ventricles.

At what structure in the transmission sequence is the impulse temporarily delayed and why?

ATRIOVENTRICULAR (AV) NODE; THIS DELAY IS IMPORTANT BECAUSE IT ENSURES THAT THE ATRIA HAVE EJECTED THEIR BLOOD INTO THE VENTRICLES FIRST BEFORE THE VENTRICLES CONTRACT. as found in easy notecards .com