Exam5 Phases of Cardiac Cycle

Question 1

(beginning @ SA node)
If (funny current) channels are open allowing Na+ to go in faster than K+ leaves. This depolarization causes the opening of the voltage-gated Ca++ channels to reach threshold and generate an action potential

Answer 1

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Question 2

Propagation of the action potential is conducted as ionic movement thru the gap junctions of the atrial intercalated discs resulting in depolarization of the atrial membrane (P wave)

Answer 2

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Question 3

Atrial contraction fxns to “top off” the ventricular filling

Answer 3

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Question 4

Simultaneously, depolarization is conducted to the AV node (which hesitates due to a minimal concentration of gap junctions) allowing for ventricular coordination

Answer 4

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Question 5

Depolarization continues thru the AV bundle (bundle of His) where there are more gap junctions and therefore more speed of propagation to

Answer 5

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Question 6

the apex of the heart to the Purkinje fibers where there are the greatest number of gap junctions and therefore the quickest speed of propagation

Answer 6

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Question 7

This disruption of the depolarization wave of the ventricles is seen as the QRS complex which masks the atrial repolarization

Answer 7

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Question 8

Ventricular contraction causes an increased ventricular pressure and a drop in atrial pressure

Answer 8

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Question 9

When the ventricular pressure exceeds the atrial pressure it forces the AV valves to close prompting the FIRST HEART SOUND

Answer 9

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Question 10

All heart valves are closed and the ventricles begin to contract leading to ISOVOLUMETRIC CONTRACTION

Answer 10

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Question 11

Once ventricular pressure surpasses the pressure of the conducting vessels, the SLV open ejecting a stroke volume of blood

Answer 11

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Question 12

causing the voltage-gated Ca++ channels to inactivate resulting in repolarization of the ventricular membranes viewed as ventricular relaxation (T wave)

Answer 12

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Question 13

As ventricular pressure falls below the conducting arteries’ pressure, the SLVs close generating the SECOND HEART SOUND

Answer 13

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Question 14

At this time, 2 events happen simultaneously:

a) Aortic rebound occurs exposing the coronary artery forcing perfusion of blood into the heart wall
b) Ventricles reach ISOVOLUMETRIC RELAXATION

Answer 14

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Question 15

When ventricular pressure is less than atrial pressure the AV valves open forcing blood flow into the ventricles starting ventricular filling

Answer 15

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