Cardiac cycle

Question 1

Heart cycle?

Answer 1

1) late diastole: both sets of chambers are relaxed and ventricles passively fill
2) atrial systole: atrial contraction forces a small amt of additional blood into the ventricles
3) isovolumetric ventricular contraction: first phase of ventricular contraction pushes AV valves closed (ventricle pressure exceeds atrial pressure) but doesnt create enough pressure to open semilunars
4) Ventricular ejection: as ventricular pressure rises and exceeds pressure in the arteries, the SL valves open and blood is ejected
5) isovolumic ventricular relaxation: ventricles relax, pressure falls so blood flows back into cups of SL valves and snaps them closed

Question 2

Does diastole or systole take up majority of cardiac cycle?

Answer 2

• diastole

Question 3

What valve do you worry about with MI that involved circumflex?

Answer 3

• mitral valve involvement

Question 4

Cardiac conduction?

Answer 4

• Sa node depolarizes
• elect activity goes to AV node via internodal pathways
• depolarization spreads more slowly across atria, conduction slows through AV node to allow for ventricle filling
• depolarization then moves through AV bundle (bundle of His) and rapidly through ventricular conducting system (L and R branches) to apex of the heart
• depolarization wave spreads from purkinje fibers upward from apex of ventricles

Question 5

Difference in membrane potentials in autorhythmic cells and contractile cells?

Answer 5

–autorhythmic cells: depolarizations rapidly spread to adjacent contractile cells through gap junctions

Question 6

When does repolarization of ventricle begin?

Answer 6

• in systole

Question 7

What causes first heart sound - lubb?

Answer 7

• av valves closing - leaflets coming together, tensing of chordae

Question 8

What will happen to lubb if mitral stenosis?

Answer 8

• sound is soft, valves are calcified

Question 9

Sound of Dupp? second heart sound?

Answer 9

• pressure drops in ventricles so blood flows retrograde back towards L ventricle and fills SL valves

Question 10

When do coronary arteries fill?

Answer 10

• during diastole

Question 11

What is louder, closing of aortic valve or pulmonic valve?

Answer 11

• pressure on aortic valve higher than pulmonic so A2 is louder than P2, A2 occurs before P2 becasue aortic ejection more rapid

Question 12

What causes splitting of S2 on inspiration?

Answer 12

• increase venous return to heart so increase pressure on R atrium and so increasing the amt of filling of right atrium and it takes longer for blood to get through pulmonary arteries and this increase in volume delays closing of pulmonic valve
• this prolongs gap between A2 and P2, more noticeable, called splitting