Physiology Brown Cardiac Electrophysiology/cardiac Cycle

Front 1

What initiates the heartbeat?

Back 1

spontaneous depolarization of the SA node

Front 2

What are I(f) channels and what ion do they transport?

Back 2

funny channels open to Na+ during phase 4 (slow diastolic depolarization)

Front 3

How does the autonomic system modulate the rate of SA node firing?

Back 3

Sympathetics: decrease the length of phase 4 depolarization by increasing funny channel activity; Parasympathetics: increase the length of phase 4 depolarization by increasing the activity of I(K+) channels and decreasing the activity of funny channels

Front 4

What is overdrive suppression of a pacemaker and which pacemaker exhibits this characteristic

Back 4

Overdrive suppression is the concept of the fastest pacemaker taking control over the heart rate. The SA node does this in the human heart

Front 5

Why is there a delay between atrial contraction and ventricular contraction?

Back 5

The 'AV Block'. The AV node conducts action potentials slowly, creating a delay between the atrial and ventricular contractions

Front 6

AV nodal conduction is dependent on what type of channels?

Back 6

voltage gated Ca++ channels

Front 7

What two things prevent re-excitation of the atria via ventricular depolarization?

Back 7

annulus fibrosis cordis and AV node refractoriness

Front 8

How is the action potential propagated through the ventricular tissue?

Back 8

passive current

Front 9

What determines if a valve is open or closed?

Back 9

the pressure differential across the valve

Front 10

What phase of the cardiac cycle is the first part of systole?

Back 10

phase 2 - Isovolumetric contraction

Front 11

During what phase is ventricular filling complete?

Back 11

phase 1b - atrial systole

Front 12

What phase is the 'C wave' seen in and what causes it?

Back 12

phase 2 - isovolumetric contraction of the ventricles causes the mitral and tricuspid valves to press into the atria, increasing their pressures as well

Front 13

During which phase is S1 heard and what causes it?

Back 13

phase 2 - isovolumetric contraction, the sound is caused by the slamming shut of the mitral and tricuspid valves

Front 14

During what phase does ejection occur?

Back 14

phase 3 - ventricular systole

Front 15

What phase is the 'V wave' seen in and what causes it?

Back 15

phase 3 - ventricular systole, the v wave is caused by blood entering the atria while the mitral and tricuspid valves are still closed, increasing the atrial pressure

Front 16

What phase is S2 heard in and what causes it?

Back 16

phase 4 - isovolumetric relaxation of the ventricles causes the aortic and pulmonary valves to slam shut

Front 17

What is the ejection fraction?

Back 17

the percent of the blood volume in the ventricles that is ejected during systole

Front 18

During what phase would you hear S3?

Back 18

phase 4 - isovolumetric relaxation

Front 19

During what phase does passive ventricular filling occur?

Back 19

phase 1a

Front 20

Label the action of the valves at each point

Back 20

Front 21

At what point in the cardiac cycle would a murmur from aortic stenosis be heard?

Back 21

between S1 and S2

Front 22

At what point in the cardiac cycle would a murmur caused by aortic incompetence be heard?

Back 22

following S2

Front 23

At what point in the cardiac cycle would a murmur caused by tricuspid or mitral valve incompetence be heard?

Back 23

between S1 and S2