Mechanical Pump/Activity of the Heart

Question 1

atria vs ventricles

Answer 1

Atria = low pressure primer pumps

Ventricles = high pressure pumps that generate force to drive blood to tissues

Question 2

separate the atria from the ventricles, and the ventricles from the great arteries (aorta, pulmonary artery)

Answer 2

valves

Question 3

The right side of the heart pumps to the ______. The left side of the heart pumps to the ______.

Answer 3

Right = lungs 
Left = peripheral circulation

Question 4

function of valves

Answer 4

• prevents the backflow of blood between the heart chambers

- open/closes in response to pressure gradients

Question 5

When do valves open? Close?

Answer 5

Valves open when the forward pressure gradient forces blood into the downstream chamber/vessel.

Valves close when the backwards pressure gradient forces blood into the upstream chamber.

Question 6

thin, flimsy valves that prevent the backflow of blood from the ventricles to the atria during systole (a little backflow causes closure)

Answer 6

AV valves

Question 7

Two AV vales:

Answer 7

Right: tricuspid valve
Left: mitral valve

Question 8

attached to the AV vales and contract during systole, pull valves inward to prevent bulging

Answer 8

papillary muscles

Question 9

stronger, heavier valves that snap to closed position when arterial pressure exceeds ventricular pressure

Answer 9

semilunar valves (aortic and pulmonary valves)

Question 10

The velocity of blood ejection across semilunar valves ___ AV valves.

Answer 10

> >

Question 11

Relative to the ventricles, AV vales are _____ valves while the semilunar valves are _____ valves.

Answer 11

inlet / outlet

Question 12

Damage to or dysfunction of chordae or papillary muscles can result in…

Answer 12

excess bulging during systole and leakage of blood in the atria.

Question 13

Which valves are more subject to abrasion?

Answer 13

semilunar valves (because of high ejection velocities)

Question 14

Most common valve disorders occur on the _____ side of the heart. Name two disorders.

Answer 14

left side

• mitral valve regurgitation
• aortic valve stenosis

Question 15

diastole vs systole

Answer 15

diastole = relaxation 
systole = contraction

Question 16

7 parts of the cardiac cycle:

Answer 16

1. ) atrial systole
2. ) isovolumic ventricular contraction
3. ) rapid ventricular ejection
4. ) reduced ventricular ejection
5. ) isovolumic ventricular filling
6. ) rapid ventricular filling
7. ) reduced ventricular filling

Question 17

waves of an EKG

Answer 17

P wave: atria contract
QRS complex: ventricles contract
T wave: ventricles relax

Question 18

What does a prolonged P-R interval on an EKG indicate?

Answer 18

delayed conduction of the SA nodal impulse to the ventricles (first-degree AV block)

Question 19

uncoordinated atrial contractions resulting from electrical signals emanating from a site other than the SA node

Answer 19

Afib

Question 20

What does the EKG look like for someone with Afib?

Answer 20

no discernable P wave

Question 21

consequences of Afib

Answer 21

leads to rapid and irregular heartbeat and symptoms such as palpitations, shortness of breath, fatigue, dizziness, chest pain, or no symptoms at all

Question 22

Why does Afib increase your risk for stroke?

Answer 22

due to the pooling of blood in the aria (particularly in the poorly stirred appendage) and development of blood clots

Question 23

Treatment options for Afib:

Answer 23

• anticoagulation (anti-thrombin or anti-factor Xa for clot prevention
• cardioversion to restore normal rhythm
• catheter ablation to scar aberrant sites of signal generation
• pacemaker implantation
• closure of left atrial appendage

Question 24

What happens during atrial systole?

Answer 24

• about 80% of blood from the great veins flows directly through the atria into the ventricles before the atria contract
• at resting HR, atrial contraction increases ventricular filling by an extra 20%
• atrial systole begins with the P-wave in an EKG
• pressure rises equally in the atria and ventricles
• 4th heart sound (S4) is caused by atrial systole

Question 25

When is ventricular volume the highest?

Answer 25

during atrial systole (end diastolic volume-- EDV)

Question 26

What happens during isovolumic ventricular contraction?

Answer 26

- ventricle begins to contract (QRS wave) - when ventricular pressure > atrial pressure, AV valves close - semilunar valves are also closed so the volume cannot change - ventricular pressure rises from atrial pressure to aortic pressure - aortic pressure at lowest point (diastolic pressure) at end of isovolumic period - when ventricular pressure > aortic pressure, semilunar valves open - 1st heart sound (S1) is produced by the closure of AV valves and the opening of the semilunars

Question 27

What happens during rapid ventricular ejection?

Answer 27

- with open semilunar valves, 2/3 of SV is ejected into the great arteries - pressures in the great arteries and ventricles is rising - pressure in the aorta reaches its peak (systolic pressure) at the end of this period

Question 28

What happens during reduced ventricular ejection?

Answer 28

- the remaining 1/3 of SV is ejected into the great arteries - pressures in the great arteries and ventricles is falling - pressures in the atria are rising as blood accumulates - ventricles are not completely empty at the end of the ejection period (~50% of EDV) - T-wave (repolarization) appears just before the end of ventricular contraction

Question 29

end systolic volume

Answer 29

the volume of blood remaining in the ventricles at the end of reduced ventricular filling

Question 30

What happens during isovolumic ventricular relaxation?

Answer 30

- as the ventricles relax, aortic pressure > ventricular pressure so the semilunars close - closure of the semilunars produce S2 - both semilunars and AV valves are closed to maintain a constant volume - ventricular pressure falls toward atrial pressures

Question 31

What happens during rapid ventricular filling?

Answer 31

- as ventricular pressures fall below atrial pressures, the AV valves open - blood stored in the atria during systole rushes into the ventricles - turbulent flow into the ventricles produces S3 (more prominent in children) - ventricular volume rises rapidly - aortic pressure falls as blood flows out into periphery

Question 32

What happens during reduced ventricular filling?

Answer 32

- ventricles continue to fill with blood flowing from the veins - ventricular volume is rising at a reduced rate - aortic pressure continues to fall

Question 33

SV

Answer 33

EDV - ESV

Question 34

ejection fraction

Answer 34

SV / EDV

Question 35

CO

Answer 35

SV x HR

Question 36

preload vs afterload

Answer 36

Preload = tension (degree of stretch) on/of muscles in the ventricle when it begins to contract (EDV) Afterload = load against which the ventricle exerts its contractile force (aortic pressure for the left heart, pulmonary artery pressure for the right)

Question 37

Describe the length-tension curve.

Answer 37

the amount of tension that develops as a function of the length of the sarcomere (actin-myosin overlap)

Question 38

Frank-Starling mechanism

Answer 38

greater distension during diastole = greater force of contraction during systole

Question 39

Three factors that affect SV:

Answer 39

contractility venous filling pressure (preload) aortic pressure

Question 40

effects of increasing contractility on SV

Answer 40

- increases in cytosolic Ca++ in a cardiomyocyte increases force generation at any given muscle length - moves point C and D in pressure-volume loop to the left (smaller ESV) - EDV unchanged, ESV reduced - SV increased due to reduced ESV

Question 41

effects of increasing venous filling pressure (preload) on SV

Answer 41

- moves points A and B in pressure-volume loop to the right (larger EDV) - increased EDV, no change in ESV - SV is increased due to larger EDV

Question 42

effects of increasing aortic pressure (afterload) on SV

Answer 42

- increasing aortic pressure increases afterload as well as EDV, leading to decreased SV - moves points C and D in the pressure-volume loop to the right (larger EDV)