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Cardiovascular system > Cardiac cycle > Flashcards

Cardiac cycle Flashcards

1
Q

What is Convection, in terms of Oxygen transport?

A

The mass movement of fluid caused by pressure difference

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2
Q

What is the main function of the heart?

A

Driving force (creates large pressure)

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3
Q

What is the main function of the Arteries?

A

Distribution (mostly in parallel alter blood flow)

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4
Q

What is the function of the Capillaries?

A

Exchange (found in a huge number, thin for ease of movement)

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5
Q

What is the function of the Veins?

A

Reservoir (2/3 of the blood volume are stored in veins and venues)

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6
Q

Why is Convection used to transport O2 instead of Diffusion?

A

Diffusion is very slow for distances greater than 1mm, therefore useless for whole body transport

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7
Q

Describe the Sinoatrial node (SAN)

A

Group of cells located in the wall of the right atrium

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8
Q

What are the functions of the SAN?

A
  • Ability to spontaneously produce action potential that travels through the heart via the electrical conduction system
  • Sets the rhythm of the heart, known as heart’s natural pacemaker
  • Rate of action potential production is influenced by nerves that supply it
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9
Q

Describe the Atrioventricular node (AVN)

A

A part of the electrical conduction system of the heart, that coordinates the top of the heart

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10
Q

What are the functions of the AVN?

A
  • Electrically connects the right atrium and right ventricle
  • Delays the impulse so that the atria have time to eject their blood into the ventricles (before ventricular contraction)
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11
Q

Describe Phase 4 of SAN pacemaker potentials:

A
  • Funny current ‘If’
  • After an SA action potential, the membrane repolarises below the ‘If’ threshold, which is approximately (-40/-50mV)
  • The funny current is then activated and supplies inwards current
  • At -50 mV the hyperpolarisation activates Na+ channels
  • Influx of Na+ ions into the cell causes a slow depolarisation: starts the diastolic depolarisation phase
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12
Q

What is the range for the normal resting negative voltage in the cell interior (compared to the cell exterior)?

A

-40 mV to -80 mV

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13
Q

What concentration of ions is high inside the SAN?

A

K+

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14
Q

What concentration of ions is high outside the SAN?

A

Na+ Cl-

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15
Q

How many ions does the sodium-potassium pump transport in and out? and what does it use to do this?

A
  • three sodium ions out of the cell
  • two potassium ions into the cell
  • uses ATP
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16
Q

Describe phase 0 of SAN pacemaker potentials?

A
  • As the cell depolarises, it reaches a threshold for voltage gated Ca2+ channels
  • This leads to a Ca2+ influx
  • RAPID depolarisation occurs
    (Voltage gated Na+ channels are not involved as in normal depolarisation)
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17
Q

Describe phase 3 of SAN pacemaker potentials?

A
  • Calcium channels switch off
  • Activation of voltage gated K+ channels
  • causes K+ efflux
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18
Q

Describe phase 0 of atria/ventricular action potentials

A

RAPID DEPOLARISATION:

  • Stimulus from SA node received, causing:
  • Voltage gated Na+ channels to open
  • Na+ influx
  • Voltage gated Ca2+ channels start to open very slowly
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19
Q

Describe phase 1 of atria/ventricular action potentials

A

EARLY DEPOLARISATION:

- Na+ channels close cells beginning to repolarise

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20
Q

Describe phase 2 of atria/ventricular action potentials

A

PLATEAU PHASE:

  • Voltage gated Ca2+ channels fully open
  • Ca2+ influx halts repolarisation
  • Voltage gated K+ channels start to open slowly
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21
Q

Describe phase 3 of atria/ventricular action potentials

A

RAPID DEPOLARISATION:

  • Ca2+ channels close
  • K+ channels open fully so K+ efflux
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22
Q

Describe phase 4 of atria/ventricular action potentials

A

RESTING PHASE:

  • Stable: Na+/K+ pump (3 Na+ out and 2K+ in)
  • Membrane slightly impermeable to Na+ but slightly permeable to K+
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23
Q

Describe the electrical conduction through the Heart

A
  • Electrical activity generated in the SA node spreads out via gap junctions into atria
  • At AV node, conduction is delayed to allow correct filling of ventricles
  • Conduction occurs rapidly through bundle of His into ventricles
  • Conduction through Purkinje fibres spreads quickly throughout the ventricles
    Ventricle contraction begins at the apex
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24
Q

P wave represents

A

Atrial depolarisation + contraction

25
Q

PR segment represents

26
Q

QRS complex represents

A

Ventricular depolarisation (atria repolarising simultaneously)

27
Q

ST segment represents

A

Time during which Ventricles are contracting and emptying

28
Q

T wave represents

A

Ventricular repolarisation

29
Q

TP interval represents

A

Time during which ventricles are relaxing and filling

30
Q

Where is electrical activity generated and conducted?

A

Electrical activity is generated at the SA node and conducted throughout the heart.

31
Q

What is electrical activity converted into and what does this lead to?

A

Electrical activity is converted into myocardial contraction which creates pressure changes within the chambers.

32
Q

Where does blood flow from and to in the heart?

A

Blood flows from an area of high pressure to an area of low pressure, unless flow is blocked by a valve.

33
Q

What does the opening and closing of a valve depend on?

A

Valves open and close depending on pressure changes in chambers

34
Q

Flow of blood through the heart

A 
Vena Cavae
Right atrium 
Tricuspid valve (AV)
Right ventricle
Pulmonary (semilunar) valve 
Pulmonary arteries 
Lung circulation 
Pulmonary veins 
Left atrium 
Bicuspid (mitral) valve (AV)
Left ventricle 
Aortic (semilunar) valve 
Aorta 
Systemic circulation
35
Q

Mean systolic/diastolic pressure in the right atrium

36
Q

Mean systolic/diastolic pressure in the left atrium

37
Q

Mean systolic/diastolic pressure in the right ventricle

38
Q

Mean systolic/diastolic pressure in the right ventricle

39
Q

Mean systolic/diastolic pressure in the pulmonary artery

40
Q

Mean systolic/diastolic pressure in the aorta

41
Q

Describe the cardiac cycle in terms of pressure and valve opening/closing: VENTRICULAR FILLING/ ATRIAL CONTRACTION

A
  • Blood enters atria and move into ventricles
  • Pressure in atria is greater than in the ventricles
  • The mitral/tricuspid valves then open, which is aided by atria contraction
42
Q

Describe the cardiac cycle in terms of pressure and valve opening/closing: ISOVOLUMETRIC CONTRACTION

A
  • Pressure in full ventricles is greater than in the atria
  • This closes the mitral and tricuspid valves
  • There is contraction of the closed ventricles
  • The pressure rises
43
Q

Describe the cardiac cycle in terms of pressure and valve opening/closing: EJECTION

A
  • Pressure in ventricles is greater than in the aorta/pulmonary artery
  • This causes the aorta and pulmonary valves to open, ejecting the blood
  • Blood enters the atria
44
Q

Describe the cardiac cycle in terms of pressure and valve opening/closing: ISOVOLUMETRIC RELAXATION

A
  • Pressure in the aorta/pulmonary artery is greater than in the ventricles
  • Aortic/pulmonary valves close
  • Closed ventricles relaxes ready to receive blood
45
Q

Equation for work

A

Work = Change in ventricle pressure x Change in volume

46
Q

Describe the ventricular pressure-volume loop

A

The loop relates to the amount of energy consumption during the cardiac cycle.

47
Q

What does the area inside the ventricular pressure-volume loop equal to?

A

The amount of stroke work done

48
Q

Describe pressure changes in left ventricle and the effects

A
  1. Contraction of left atrium, so ventricular pressure rises slightly. The mitral valve closes the ventricle, and so the pressure is greater than atrial pressure.
  2. Pressure rises during isovolumetric contraction
  3. When ventricle pressure increases in the aorta, the aortic valve opens and blood is ejected
  4. The ventricle empties and so ventricle pressure is decreased in the aortic valve and so the valve closes. Isovolumetric relaxation occurs and a large pressure drop means that the mitral valve opens
49
Q

Describe volume changes in the left ventricle and the effects

A
  1. Filling of the ventricles result in the contraction of the atria (end diastolic volume=120ml)
  2. Full ventricle means the higher pressure closes the mitral valve. Systole occurs and so no change in volume.
  3. Ventricular pressure overcomes aortic valve and so blood is ejected
  4. When ventricular pressure falls, the aortic pressure closes aortic valve, isovolumetric ventricular relaxation.
50
Q

End Diastolic Volume

51
Q

End Systolic Volume

52
Q

Stroke Volume

A

EDV - SV = 120 - 40 = 80 ml

53
Q

Describe the sounds of the heart

A

They are vibrations induced by closure of cardiac valves, vibrations in ventricular chambers or turbulent blood flow through the valves

54
Q

what causes S1: ‘Lub’?

A

Closure of tricuspid/mitral valves at the beginning of ventricular systole

55
Q

what causes S2: ‘Dub’?

A

Closure of aortic/pulmonary valves (semilunar valves) at the end of ventricular systole

56
Q

what causes S3: ‘Occasional’?

A

Turbulent blood flow into ventricles, detected near end of first 1/3 diastole (especially in older people)

57
Q

what causes S4: Pathological in adults?

A

Forceful atrial contraction against a stiff ventricle less so in young people

58
Q

Summary of cardiac cycle (7 points)

A
  1. Atrial contraction
  2. Isovolumetric ventricular contraction
  3. Rapid ventricular ejection
  4. Reduced ventricular ejection
  5. Isovolumetric ventricular relaxation
  6. Rapid ventricular filling
  7. Reduced ventricular filling

Cardiovascular system (16 decks)

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