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Bioregulatory systems 3 > Cardiac cycle > Flashcards

Cardiac cycle Flashcards

1
Q

What are the 2 main phases of each heart beat?

A

Diastole(relaxation-ventricles fill with blood)-lasts approx 2/3 of each beat

Systole(contraction-ventricles eject blood into arteries)-approx 1/3 of each beat

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2
Q

What is the end diastolic volume?

A

When the ventricles are filled with blood completely(before contraction) 108ml

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3
Q

What is end systolic volume?

A

the remaining volume in the ventricle When the blood is ejected from ventricles 36ml

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4
Q

What is stroke volume at rest?

A

End diastolic volume- end systolic volume= stroke volume (72ml)

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5
Q

What is the ejection fraction? How do you calculate it?

A

the percentage of blood ejected from the heart 100x stroke volume/end diastolic volume 100x72/108=67%

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6
Q

How is ejection fraction used?

A

Used clinically to describe the contractility of the heart in a patient who is breathless and has heart failure they would have an ejection frsaction close to 35/40%

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7
Q

What is the first stage of the cardiac cycle?

A

ATRIOLE SYSTOLE-atria almost from passive filling driven by pressure gradient

Atria contract to top up the volume of blood in the ventricles

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8
Q

How is atrial systole represented on an ECG?

A

P-wave

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9
Q

What is the 4th heart sound?

A

abnormal sound in the ATRIOLE SYSTOLE part of the cardiac cycle caused by cognitive heart failure, pulmonary embolism or tricuspid incompetence indicated on the ECG by s4

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10
Q

What is the second phase of the cardiac cycle?

A

ISOVOLUMETRIC CONTRACTION:

  • Interval between the AV valves closing and the SL valves opening (so both valves are closed)
  • contraction of the ventricles with NO CHANGE IN VOLUME but increased pressure caused by VENTRICULAR DEPOLARISATION
  • QRS COMPLEX -marks the start of ventricular depolaristion
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11
Q

What is the 1st heart sound(S1)?

A

LUB sound due to the closure of the AV valves and assosiated vibrations

-Part of Isovolumetric contraction phase

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12
Q

What is the 3rd stage of the cardiac cycle?

A

RAPID EJECTION:

  • opening of the aortic and pulmonary valves mark the start of this phase
  • as the ventricles contract the pressure within them exceeds pressure in the aorta and pulmonary arteries
  • SL valves open, blood pumped out and the volume of the ventricles DECREASES
  • no heart sound for this phase
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13
Q

What is the 4th phase of the cardiac cycle?

A

REDUCED EJECTION:

  • this phase marks the end of systole
  • the AORTIC AND PULMONARY valves begin to close due to reduced pressure gradient
  • blood flow from the ventricles to the arteries( aorta and pulmonary) decrease and ventricular VOLUME DECREASES more slowly
  • pressure in the ventricles fall below pressure in the aorta/arteries causing blood to begin to flow backward and therefore causing the SL valves to shut close
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14
Q

What is the 5th stage of the cardiac cycle?

A

ISOVOLUMETRIC RELAXATION:

  • no change in volume occuring because all sets of valves are closed
  • AV valves remain closed until the ventricular pressure drops below atrial
  • atrial pressure RISES
  • s2 heart sound(dub) due to the closure of the SL valves
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15
Q

What is the 6th stage of the cardiac cycle?

A

RAPID PASSIVE FILLING:

  • blood passively fills the ventricles once AV valves open
  • occurs during isoelectric ECG between cardiac cycles
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16
Q

What is the abnormal heart sound that could occur during rapid passive filling?

A

3rd sound -usually abnormal and may signify turbulent ventricular filling

-can be due to severe hypertension or mitral incompetence

17
Q

What is the last stage of the cardiac cycle?

A

REDUCED PASSIVE FILLING :

  • can also be called diastasis
  • ventricular volume fills more slowly
  • The ventricles will continue to fill quite a lot without atrial contraction,till eventually the cycle starts again with atriol systole
18
Q

How are the patterns of pressure changes different in the left and right ventricle?

A
  • basically identical
  • however proportionately the pressure in the right heart and pulmonary circulation are much lower
  • despite the lower pressure the right ventricle still ejects the same VOLUME of blood
19
Q

Where do pressure changes take place in the heart?

A
  • Right atrium to the right ventricle(via tricuspid valve)
  • right ventricle to pulmonry artery via pulmonary velave
20
Q

Describe pressure volume loops?

A

A-At the end of diastole the Left ventricular volume is high because the ventricle is filled with blood but it is relaxed so the pressure is LOW

B-then before the aortic pressure is encountered the pressure in the ventricles increase greatly. No change in volume(isovolumetric contraction)

C- At the end of systole the volume of the left ventricle is decreased as the ventricles have emptied themselves of blood but the pressure is the same(reduced ejection)

D-Then the pressure in the left ventricle decreases due to ISOVOLUMIC RELAXATION (atrium filling) but the volume is the same Then the cycle starts again

21
Q

What are the clinical relevance of pressure volume loops?

A

They give you an idea of the contractility of the heart

22
Q

How does changing the preload and afterload effect the pressure volume loops?

A

The volume of blood filling the ventricles during diastole determines the PRELOAD that stretches the resting venticular muscle(point A) -The blood pressure in great vessels(aorta and pulmonary artery) represent the AFTERLOAD(point B)

23
Q

What does an increase in preload cause?

A

increase in stroke volume Frank starling relationship -

24
Q

What does an increase in afterload cause?

A

decreases stroke volume because the amount of shortening of the muscles that occur decreased

25
Q

How do calculate cardiac output?

A

heart ratex stoke volume

26
Q

What 3 things effect the heart rate and stroke volume?

A

Preload Afterload contractility

27
Q

What is the definition of contractility?

A

the measure of the strength of contraction of the heart and it is changed by sympathetic stimulation

28
Q

What is the diachrotic notch?

Where in the cardiac cycle does it occur?

A

It is the green line in the yellow zone of the picture

In the 5th part of the cardiac cycle

increase in aortic pressure due to rebound pressure from the closure of the aortic valve.

Bioregulatory systems 3 (11 decks)

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