A & P - Cardiovascular System, The Heart - Cardiac Cycle

Front 1

What is the function of the papillary muscles?

Back 1

The papillary muscles contract when the ventricles contract, working to stabilize the atrioventricular valves against the rising ventricular pressure.

When the ventricles contract, blood pressure pushes the valves closed. Pressure in the ventricles can be very high, however, and the contraction of the muscles keeps the valve leaflets steady to prevent backflow into the atria

Front 2

Describe blood flow through the systemic and pulmonary circulations, beginning with deoxygenated blood at the tissues:

Back 2

1) Deoxygenated blood from tissues flows through capillaries, then venules, then veins to either the superior or inferior vena cava, finally entering the right atrium of the heart.

2) Flows past the tricuspid valve in the right ventricle of the heart

3) Flows past the pulmonary valve into the pulmonary trunk and on into the right and left pulmonary arteries

4) Flows through arterioles and eventually pulmonary capillaries where it undergoes gas exchange with the alveolar air (external respiration)

5) Oxygenated blood flows through pulmonary veins (x4) to the left atrium

6) Flows past the mitral valve into the left ventricle

7) Flows past the aortic valve into the ascending aorta and onwards to the tissues

Front 3

At what point during the cardiac cycle is blood perfusing the myocardium? Why is this?

Back 3

Perfusion occurs during ventricular diastole because the contractions of the ventricles during systole squeeze shut the penetrating coronary vessels

Front 4

At what point during the cardiac cycle is the volume of blood in the ventricles at its maximum?

Back 4

At the very end of ventricular diastole, just after the atria have contracted

The volume of blood in the ventricles at this time is called the end diastolic volume (EDV)

Front 5

What is the etymology of diastole?

Back 5

Greek, a drawing up or contraction

Front 6

What is the etymology of diastole?

Back 6

Greek, a putting asunder or dilation

Front 7

What's happening during ventricular diastole?

Back 7

Blood flows through the atria and into the ventricles, pressure in the ventricles rises ever so slowly as they fill

The cusps of the AV valves begin to close

At the end of diastole, the atria contract (atrial systole) pushing a final bolus of blood into the ventricles before they contract

Front 8

What is the isovolumetric contraction phase of the cardiac cycle?

Back 8

Time during which ventricles are contracting but blood is neither leaving nor entering the ventricles

Occurs during ventricular systole when ventricular pressure is great enough to shut the AV valves but not yet great enough to push blood through the semilunar valves

Front 9

Which phase follows the isovolumetric contraction phase of the cardiac cycle?

Back 9

Ventricular ejection phase

Occurs when pressure inside ventricles exceeds systemic pressure (80 mmHg) and blood bursts through the SL valves into the ascending aorta and pulmonary trunk, respectively

Front 10

What phases and events occur during ventricular diastole?

Back 10

Ventricular myocardium depolarizes and begins to contract

Pressure within ventricles increases substantially

AV valves forced shut, contraction of papillary muscles keeps them from prolapsing

Isovolumetric contraction phase

Ventricular ejection phase (blood pushes through SL valves and into the pulmonary trunk and ascending aorta)

Front 11

What is the volume of blood remaining in the ventricles after systole called?

Back 11

End systolic volume (ESV)

Front 12

Beginning in early ventricular diastole, describe the events of the cardiac cycle:

Back 12

1) AV valves are open and blood from the atria is filling the ventricles

2) Atrial systole occurs and end-diastolic volume is reached

3) Ventricles contract and pressure in them rises dramatically, forcing the AV valves closed

4) Isovolumetic contraction phase

4) Pressure in the ventricles exceeds pressure in the aorta and pulmonary trunk and the SL valves are forced open

5) Ventricular ejection phase

6) Pressure in the ventricles drops to the point that backflow closes SL valves and increased pressure in atria forces open the AV valves

Front 13

At what point in the cardiac cycle do the AV valves open? Why?

Back 13

Ventricular diastole, when pressure in the atria exceeds that in the ventricles

Front 14

At what point in the cardiac cycle do the AV valves close? Why?

Back 14

Ventricular systole, when pressure in the ventricles exceeds that in the atria

Contraction of the papillary muscles ensures they stay closed against the rising tide

Front 15

At what point in the cardiac cycle do the SL valves open? Why?

Back 15

Ventricular systole, after the isovolumetric contraction phase

Pressure in the ventricles exceeds that in the aorta and pulmonary trunk, forcing the valves open

Front 16

At what point in the cardiac cycle doe the SL valves close? Why?

Back 16

Ventricular diastole, after the ventricular ejection phase

Pressure in the ventricles drops below that in the aorta and pulmonary trunk, causing backflow towards the SL valves, forcing them shut

Front 17

What mechanical event is responsible for S1?

Back 17

The closing of the AV valves causes S1.

S1 thus marks the end of diastole and the beginning of systole

Front 18

What mechanical event is responsible for S2?

Back 18

The closing of the SL valves causes S2.

S2 thus marks the end of the ventricular ejection phase (systole) and the beginning of diastole

Front 19

Which phase of the cardiac cycle happens between S1 and S2?

Back 19

Ventricular systole (isovolumetric contraction, ventricular ejection)

Front 20

What phase of the cardiac cycle happens between S2 and S1?

Back 20

Ventricular diastole (ventricular filling, atrial systole at the very end)

Front 21

Must make a card about the various pressures of the heart during different times of the cardiac cycle

Back 21

...

Front 22

Describe the timing of papillary muscle contraction in relation to ventricular contraction

Back 22

Papillary muscles depolarize and contraction a fraction ahead of the ventricular myocardium so as to allow them time to close before blood is pushed hard against the valves