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Flashcards in Cardiac cycle Deck (16)
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What are the phases of the cardiac cycle

1a. Rapid ventricular filling
1b. Diastasis - ventricular filling has slowed
1c. Atrial systole
2.Isovolumetric contractions- ventricles contract with no volume change as all valves are closed
3. Pressure in ventricles exceeds that of the aorta/pulmonary arteries so semilunar valves open and blood is ejected from the ventricles
4. Isometric relaxation - Ventricles relax with no change in volume as all valves are closed


What does the P wave show

The start of atrial muscle contraction


How much blood does atrial contraction add to the ventricles

Only a small amount - rapid filling stage has already taken place - Causes an increase in both atrial and ventricular pressures


What Occurs during the QRS complex

Ventricular depolarization


Why does pressure rise in the atria during ventricular depolarisation

Because mitral or tricuspid valve both push back into the atria due to the increased ventricular pressure


What is sound S1 produced by on the echocardiogram

The closing of the mitral and tricuspid valves


Does ventricular volume after systole drop to 0

No - end systolic blood volume remains


What increase occurs in the rate of flow through the aorta after ventricular systole

0-5m/s very rapidly - Rate then falls and even drops below 0 - retrograde flow - this blood goes into the coronary sinus


How is the S2 sound generated

Through the closure of the Aortic and pulmonary valves


What does the A wave for the jugular pulse reflect?

Atrial contraction


What does the jugular venous pressure mimic

Atrial pressure


What does the C wave reflect

Bulging of the bicuspid or tricuspid valve back up into the atria during ventricular systole


What does the X descent reflect

As the heart ejects blood is is laterally and caudally displaced - this stretches the veins attached to it and stretches them; increasing their volume and causing their pressure to fall


Why does the right atria contract before the left?

Because the SAN is found on the right atrial wall, so their muscles are depolarised first


Why does the left ventricle contract before the right?

Due to the anatomical distribution of the Purkinje fibres and Bundle of His


Why is ejection from the right ventricle before that of the left?

Because pulmonary artery pressure is lower than that of the aorta so less work is needed to increase the ventricular pressure above that of the pulmonary artery .