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CVS II > Cardiac cycle > Flashcards

Cardiac cycle Flashcards

1
Q

Why can’t you rely of diffusion for O2 transport?

A

slow for distances >1 mm

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2
Q

Whens diffusion used + for which distances?

A

O2 at lungs 0.3μm

O2 at tissues 10μm

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3
Q

Define convection

A

mass movement of fluid due to p diff

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4
Q

Role of heart in convection?

A 
driving force (creates large pressures)
ejects blood into arteries
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5
Q

Role of arteries in convection?

A

distribution (alter blood flow)

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6
Q

Role of capillaries in convection?

A

solute/fluid exchange (many 1 cell thick)

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7
Q

Role of veins in convection?

A

reservoir (2/3ths of blood v)

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8
Q

What’s the SAN?

A

in RA generates pacemaker potentials

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9
Q

Describe the phases of pacemaker potential

A 
4= unstable RMP due to Iᶠ (hyperpolarision-activated Na channel), Na+ influx - depolarisation
0= threshold reached, depolarisation activates vgcc, Ca2+ influx
3= vgcc switch off, vgKc activated, K+ efflux, repolarisation back to 4
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10
Q

How’s Iᶠ activated?

A

hyperpolarision-activated Na channel

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11
Q

Describe the phases of atrial + ventricular contraction

A

0= activated vgNac, Na+ inlfux, rapid depolarisation
1= vgNa switch off, repolarisation
2= plateau due to vgcc activated, Ca2+ influx, CICR, refractory period so no AP
3=vgcc close, vgKc repolarisation, K+ efflux, back to RMP

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12
Q

What happens during plateau phase?

A

vgcc activated, Ca2+ influx:

CICR + refractory period so no AP (no twitching cardiac muscle fibrillation) to allow refilling

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13
Q

Describe conduction through the heart

A
  • SAN electrical activity spreads out via gap junctions into atria
  • AVN slows electrical activity to allow ventricles to fill
  • rapid conduction at Bundle of His L+R branches to ventricles
  • conduction via Purkinje fibres spread throughout ventricles
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14
Q

Where does contraction begin?

A

apex depolarised first to allow ejection

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15
Q

What does ECG represent?

A

electrical activity + conduction

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16
Q

What’s P wave?

A

atrial depolarisation

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17
Q

What’s PR segment?

A

AVN delay

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18
Q

What’s QRS complex?

A

Ventricular depolarisation (atria repolarising simultaneously)

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19
Q

What’s ST segment?

A

Time when ventricles contract+empty

20
Q

What’s T wave?

A

ventricular repolarisation

21
Q

What’s TP interval?

A

Time when ventricles relax + fill

___________

22
Q

How long is systole + dystole?

A
  1. 34s

0. 66s

23
Q

Describe the blood flow via heart

A
  • venous return from SVC + IVC -RA
  • tricuspid valve
  • pul valve
  • pul arteries
  • LUNG CIRCULATION
  • pul veins
  • LA
  • mitral valve
  • LV
  • aortic valve
  • aorta
  • SYSTEMIC CIRCULATION
24
Q

What are the systolic/diastolic p in the heart in mmHg?

A 
RA: 1-5
RV: 25/5
Pul Artery: 25/10
LA: 5
LV: 120/5
Aorta: 120/80
25
Q

Describe stages of cardiac cycle

A

1) Diastole - ventricle filling, atrial contraction
2) Systole - ventricular isovolumetric contraction (v stays same but p increases)
3) Diastole - eject, atrial filling
4) Systole - ventricular isovolumetric relaxation

26
Q

Describe 1) of cardiac cycle

A

Ventricular filling/atria contraction

  • blood enters atria, moves into ventricles
  • atria p > ventricles
  • tri/bicuspid valves open
  • filling aided by atria contraction
27
Q

Describe 2) of cardiac cycle

A

Isovolumetric contraction

  • ventricle p > atria
  • tri/bicuspid valves close
  • contraction on closed ventricle
  • p ↑ in chamber
28
Q

Describe 3) of cardiac cycle

A

Ejection

  • ventricle p> aorta/pul artery
  • aortic/pul valves open
  • ejection
  • blood also enter atria
29
Q

Describe 4) of cardiac cycle

A

Isovolumetric relaxation

  • aorta/pul artery p> ventricles
  • aortic/pul valves close
  • ventricle relaxes to receive blood
30
Q

How much blood does the LV hold?

A

120ml is End Diastolic Volume

31
Q

What’s the End Systolic Volume?

A

40ml

32
Q

What’s SV?

A

EDV - ESV = SV

120 - 40 = 80ml

33
Q

What’s ejection fraction?

A

SV/EDV

34
Q

What are the features of p-v loop curve?

A
  • Loop area = stroke work (change in ventricle p x change in v)
  • E consumption during cardiac cycle
  • Shows O2 demand of heart
35
Q

What’s A wave?

A

Increase in venous p due to atrial contraction, tricuspid opens

36
Q

What’s X wave?

A

Drop in atrial/venous p due to atrium relaxing, then filling, tricuspid closes

37
Q

What’s V wave?

A

Increase in p due to refilling atria, atrium tense, tricuspid closed

38
Q

What’s Y wave?

A

Drop in atrial p due to atria emptying, tricuspid opens

39
Q

What are the pulsatile collapse in neck veins?

A

X + Y drops in p

40
Q

Why measure JVP?

A

see if p in RA raised

41
Q

Why would there be a greater height of venous distension?

A

R heart failure, pul artery hypertension

RV ejects less blood so left in chamber after systole so atria pumps against greater p

42
Q

What’s S1?

A

“Lub”

Closure of tricuspid/mitral values beginning of ventricular systole

43
Q

What’s S2?

A

“Dup”

Closure of aortic/pul valves beginning of ventricular diastole

44
Q

What’s S3?

A

Occasional

Turbulent blood flow into ventricles heard at end of first 1/3 diastole

45
Q

What’s S4?

A

Pathological in adults

Forceful atrial contraction against stiff ventricle

CVS II (19 decks)

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