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Cardiovascular > Cardiac Cycle > Flashcards

Cardiac Cycle Flashcards

1
Q

What are the two types of circulation in the heart ?

A

1) systemic = high pressure

2) pulmonary = low pressure system

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2
Q

Define systole

A

Contraction and ejection of blood from ventricles

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3
Q

Diastole

A

Relation and filling of ventricles

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4
Q

Average stroke volume for a 70kg man

A

70ml blood

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5
Q

Define stroke volume

A

Volume of blood ejected from each ventricle per beat

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6
Q

Are cardiac action potentials longer or shorter than the usual action potentials in eg neuronal cells ?

A

Much longer - lasts for 280ms

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7
Q

What are chordae tendineae

A

They are also known as ‘ heart strings’

  • they are tendon resembling fibrous chords of connective tissue that connect the papillary muscles to tricuspid and bicuspid valve.
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8
Q

Functions of the papillary muscles

A
  • they are found in both ventricles
  • they attach to the tricuspid and bicuspid values via chordae tendineae.
  • they contract to prevents inversion of valves during systole
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9
Q

How many phases can the cardiac cycle be split into ?

A

7

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10
Q

List all 7 phases of the cardiac cycle

A

1) atrial contraction
2) isovolumetrric contraction
3) rapid ejection
4) reduced ejection
5) isovolumetric relaxation
6) rapid filling
7) reduced filling

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11
Q

What is the total duration of all 7 phases ?

A

0.9 s

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12
Q

In one heart beat , there are … systole and … diastole

A

1 and 1

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13
Q

Wiggers diagram

A

Insert image

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14
Q

What occurs during atrial contraction : the first phase ?

A
  • atria contract , which causes an increase in pressure
  • AV vales are open
  • semi lunar valves are closed
  • this is called an A wave.
  • on an ECG : this is called a P wave.
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15
Q

What percentage of ventricular filling does atrial contraction account for ?

A

10%

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16
Q

At the end of phase 1, are ventricular volumes maximal or minimal ?

A

Maximal

  • this is termed end diastolic volume ( EDV) - 120 ml
17
Q

What occurs during isovolumetric contraction ?

A

1) mitral valve closes because ventricular pressure exceeds atrial pressure
- ventricles contract which causes rapid rise in ventricular pressure
- ALL valves are closed
- QRS complex signifies onset of ventricular depolarisation
- EDV remains the SAME because no change in volume due to ALL valves being the same

18
Q

What occurs during phase 3: rapid ejection

A

1) AORTIC VALVE opens because ventricular pressure exceeds aortic pressure
- causes ejection of blood into aorta
- rapid decrease in ventricular volume as blood is ejected into aorta
- atrial pressure initially decreases as atrial base pulled downwards when ventricles contract = X descent

19
Q

What occurs during phase 4: reduced ejection

A

1) repolarisation of ventricles lead to a decline in tension and rate of ejection begins to fall
2) atrial pressure gradually rises due to continued venous return from lungs = V wave
3) T wave on ECG

20
Q

What occurs during phase 5: isovolumetric relation

A

1) aortic valves close because ventricle pressure falls below aortic pressure
2) dicrotic notch in aortic pressure curved caused by valve closure
3) rapid decline in ventricular pressure, but volume remains the same because all valves close

You get end systolic volume .

21
Q

WHat occurs during phase 6 : rapid filling

A

1) mitral valves open because atrial pressure exceeds ventricular
2) fall in atrial pressure after mitral valves open is called Y descent
3) rapid ventricular filling occurs

22
Q

What occurs during phase 7: reduced filling ?

A

Rate of filling slows down as ventricle reaches relaxed volume.

  • this is called diastatis
23
Q

What is responsible for the S1 sound in a phonocardiogram ?

A

Closure of the mitral valves during phase 2: isovolumetric contraction.

24
Q

What is responsible for the S2 sound in the phonocardiogram?

A

Closure of the semi lunar valves during phase 5: isovolumetric relaxation

25
Q

What is responsible for the S3 sound ?

A

Ventricular filling is normally silent . However m third heart sound sometimes present in children , but could be a sign of pathology in adults. Occurs during phase 6- rapid filling

26
Q

What are two forms of abnormal valve function ?

A

1) stenosis

3) regurgitation

27
Q

What is stenosis ?

A

Valve doesn’t open enough which results in obstruction to blood flow when valve would normally open

28
Q

What is regurgitation ?

A

Valve doesn’t close all the way , leads to back leakage when valve should be closed

29
Q

What causes aortic valve stenosis ?

A

1) chronic rheumatic fever which results in inflammation
2) congenital cause eg born with bicuspid form of valve
3) degenerative cause eg calcification

30
Q

What are the consequences for aortic valve stenosis ?

A
  • less blood can get through to valve
  • increased left ventricular pressure due to having to work much harder
  • results in left ventricular hypertrophy

OR it could lead to left sided heart failure which is characterised by angina ( tightening of the chest) and syncope ( fainting )

31
Q

What is the cause of aortic valve regurgitation?

A

1) aortic root dilation ( leaflets pulled apart)

2) valvular damage due to rheumatic fever

32
Q

What are the consequences of aortic valve regurgitation?

A
  • blood flows back into left ventricle during diastole
  • increases stroke volume as more blood is coming back so more blood to pump
  • systolic pressure increases and diastolic pressure decreases
  • leads to bounding pulse ( head bobbing , beds of nails go red and pale with each beat - QUINKES sign)
  • Left ventricular hypertrophy
33
Q

What is the main cause for mitral valve stenosis ?

A

Rheumatic fever (99.9% cases)

34
Q

What are the consequences for mitral valve stenosis ?

A

Increased left atrium pressure because harder for blood to flow from left atrium to left ventricle

35
Q

Left atria dilation is a consequence of increased left atrial pressure due to mitral valve stenosis , what are the consequences of increased left atrial dilation ?

A
  • these leads to left atrium dilation which could lead to oesophagus compression which then leads to dysphagia ( swallowing difficulties)
  • or the artrial dilation could lead to atrial fibrillation which would lead to thrombus formation.
36
Q

What are a few other consequences of increased left atrial pressure ( mitral valve stenosis) - other than left atrial dilation ?

A
  • pulmonary oedema (accumulation of fluid within the air spaces and tissues of the lungs) m
  • pulmonary hypertension ( increased blood pressure within the arteries of the lungs)
  • dyspnea ( shortness of breath)
37
Q

What are the causes of mitral valve regurgitation?

A

1) damage to papillary muscles after heart attack
2) myxomatous ( thickening and weakening of mitral leaflets and tendonae) degeneration can weaken tissue leading to prolapse
3) rhetumatic fever which leads to leaflet fibrosis
4) Left sided heart failure leads to left ventricle dilation which can stretch valve

38
Q

What are the consequences of mitral valve regurgitation?

A
  • as some blood leaks back into left atrium , this increases preload as more blood enters LV in subsequent cycles .. this causes hypertrophy of LV

Cardiovascular (18 decks)

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