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BMS10 > Regulation of Cardiac Function 1 > Flashcards

Regulation of Cardiac Function 1 Flashcards

1
Q

What are the steps of the cardiac cycle?

A
  1. Diastole (passive filling)
  2. Atrial systole
  3. Ventricular systole (isovolumetric contraction)
  4. Systole (ejection)
  5. Diastole (isovolumetric relaxation)
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2
Q

What occurs during diastole (passive filling)?

A

Blood flows into heart from vena cava and pulmonary veins

AV valves open; semilunar valves closed

Consistent pressure increase in atria and ventricles

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3
Q

What occurs during atrial systole?

A

Last of blood ejected from atria into ventricles

Small increase in pressure in both atria and ventricles

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4
Q

What occurs during ventricular systole (isovolumetric contraction)?

A

No flow as all valves closed

Pressure increases sharply in ventricles with no change in volume

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5
Q

What occurs during systole?

A

Ejection of blood

Ventricular pressure > outflow vessel pressure so semilunar valves open

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6
Q

What occurs just before and during diastole (isovolumetric relaxation)?

A

Ejection slows as ventricular contraction loses force

When ventricular pressure falls below pressure of outflow vessels, semilunar valves close

Rapid decrease in ventricular pressure without changing volume

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7
Q

What aids ventricular filling?

A

Elastic recoil of ventricle walls

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8
Q

What is the dicrotic notch?

A

Aortic pressure trace dips when aortic valve closes due to brief backflow of blood against valve

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9
Q

What percentage of ventricular filling is accounted for by atrial systole?

A

<20%

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10
Q

Why does the atrial pressure increase slightly during systole?

A

Ventricular contraction causes flexible AV valve to bulge into atrium

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11
Q

What does an electrocardiogram do?

A

Measures electrical activity of heart

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12
Q

What are the waves shown on a typical electrocardiogram caused by?

A

P - atrial depolarisation

QRS complex - ventricular depolarisation

T - ventricular repolarisation

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13
Q

Approximately how much time passes between P and R on an ECG?

A

120ms

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14
Q

Approximately how much time passes during the QRS complex on an ECG?

A

80ms

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15
Q

Approximately how much time passes between Q and T on an ECG?

A

300ms

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16
Q

What does a phonocardiogram do?

A

Measures heart sounds

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17
Q

What causes the S1 on a phonocardiogram?

A

AV valves closing (initiation of ventricular systole)

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18
Q

What kind of sound does the closing of the AV valves create?

A

Low frequency ‘lub’

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19
Q

What causes the S2 on a phonocardiogram?

A

Semilunar valves closing

20
Q

What kind of sound does the closing of the semilunar valves create?

A

High frequency, short ‘dup’

21
Q

What causes the S3 on a phonocardiogram?

A

Opening of AV valves and rapid refilling

22
Q

What causes the S4 on a phonocardiogram?

A

Atrial systole (due to blood flow in) when end diastolic pressure is raised

23
Q

What happens to the heart sounds when end diastolic pressure is raised?

A

S4 is heard

S3 and S4 give rise to a galloping rhythm

24
Q

What causes heart murmurs?

A

Turbulent blood flow

25
Q

What causes turbulent flow in the heart?

A

Increased blood velocity

Exercise

26
Q

What can increase blood velocity in the heart?

A

Stenosis

27
Q

What kind of murmur does mitral stenosis cause?

A

Diastolic murmur as ventricle fills

28
Q

What kind of murmur does aortic stenosis cause?

A

Systolic murmur

29
Q

What murmur does mitral valve incompetence cause?

A

Systolic murmur (“lush” from blood flowing into left atrium during contraction)

30
Q

What murmur does aortic valve incompetence cause?

A

Early diastolic murmur with softening and prolongation of S2 (blood flows into heart from aorta)

31
Q

How can pulsing veins in the neck show valve incompetence?

A

Reclining patient sat upright - if pulsing stops then pulse was in jugular vein

Incompetence of tricuspid valve

32
Q

What can cause valve incompetence?

A

Endocarditis

33
Q

What is endocarditis?

A

Rare life-threatening inflammation of lining of heart muscles/valves

34
Q

What can cause endocarditis?

A

Bacterial infection during dental procedures

Severe gum disease

35
Q

What influences stroke volume?

A

Energy of ventricular contraction

Resistance to outflow from left ventricle/TPR

36
Q

What affects the energy of ventricular contraction?

A

Preload/filling pressure of right heart which in turn influences diastolic stretch

Sympathetic innervation

37
Q

What was the Otto Frank experiment?

A

Frog hearts connected to a fluid reservoir at varying heights to see effect of filling pressure on contractile force

38
Q

How does filling pressure affect contractile force (relationship)?

A

Increased filling pressure increases contractile force (and ventricular pressure)

39
Q

What is the Frank-Starling law?

A

Energy of heart contraction increases as a function of diastolic distention/stretching

40
Q

Why does increased filling pressure increase contractile force?

A

Increased stretch/distention

Increased initial muscle fibre length

Increased cross-bridging

Increased tension

41
Q

What is the optimal length of a sarcomere to maximise contractile force?

A

1.75-2.25um

42
Q

Why would overstretching a sarcomere result in no/less tension formed?

A

Little/no overlap of actin and myosin

So little/no cross-bridging

43
Q

Why does heart failure decrease contractile force?

A

Enlargement of cardiac myocytes and ventricles

Inappropriate alignment of actin and myosin

44
Q

How does sympathetic stimulation affect the EDP/stroke volume graph and why?

A

Upward shift

Stimulation affects contractility not EDP/volume entering

45
Q

How will increasing the stroke volume of the left heart affect the stroke volume of the right heart?

A

Increase as it’s a closed/loop system

BMS10 (13 decks)

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