Cardiac Cycle

Question 1

What is the basic structures of the body’s pumping system?

Answer 1

the heart is two pumps in series with a low pressure pulmonary circulation and a high pressure systemic

Question 2

True or false, the output of the left and right sides of the heart must be equal over time

Answer 2

true

Question 3

what is systole and diastole

Answer 3

sys is the contraction and ejection of blood from the ventricles. dia is the relaxation and filling of the ventricles

Question 4

what are the typical pressures in the heart during systole and diastole

Answer 4

LA 8 to 10, LV 120/10, RA 0 to 4, RV 25/4

Aorta 120/80 (elastic recoil), PA 25/10

Question 5

what is the stroke volume

Answer 5

the amount of blood each ventricle pumps each beat about 70ml

Question 6

what allows the heart to contract so efficiently and coordinated

Answer 6

cell tightly integrated by gap junctions, allowing the wave to depolarisation to travel easily

Question 7

how long is a cardiac action potential

Answer 7

280ms for a single contraction

Question 8

what are the four heart valves and what causes them to open or close

Answer 8

the tricuspid (RAV), mitral (LAV), pulmonary and aortic. differential pressures in the chambers

Question 9

how are the cusps of the mitral and tricuspid prevented from inverting during systole

Answer 9

through chordae tendineae which attatch to papillary muscles

Question 10

Outline the electrical process of systole

Answer 10

pacemaker cells in SAN generate an action potential, which spreads over the atria causing atrial systole. Impulse reaches AVN where it is delayed for 120ms before spreading down the ventricular septum to apex. Ventricles contract from the apex to the base and from inner to outer myocardium forcing blood through the PV and AV

Question 11

what are the 7 phases of the cardiac cycle

Answer 11

1 atrial contraction, 2 isovolumetric contraction, 3 rapid ejection, 4 reduced ejection, 5 isovolumetic relaxation, 6 rapid filling, 7 reduced filling.

Question 12

which of the phases are diastole and which are systole and how long do they last

Answer 12

2-4 is systole and lasts 0.35s. 1,5-7 are diastole and can change depending on cardiac output need usually 0.55s for 67bpm

Question 13

Which two ways are the ventricles filled

Answer 13

90% passive filling, 10% through atrial contraction

Question 14

What are features of phase 1

Answer 14

A wave in wigger’s diagram due to atrial pressure rise during atrial systole

P wave in an ECG (atrial depolarisation)

Set up of End diastolic volume (EDV) 120ml

Mitral and tricuspid open. AV and PV closed

Question 15

What are the features of phase 2

Answer 15

C wave and S1 due to closing of mitral valve (LVP>LAP)
Rapid rise in ventricular pressure
Isovolumetric
QRS complex in ECG significes ventricular depolarised

Question 16

What are features of phase 3

Answer 16

X descent as atrial base pulled down by Ventricular contraction
Aortic valve opens (LVP>AorticP)
Rapid decrease in ventricular volume as blood ejected
AtrVen valves closed`

Question 17

what are the features of phase 4

Answer 17

V wave (Atrial pressure inc) due to venous return
Repolarisation leads to reduced ejection
T wave in ECG indicates ventricular repolarisation

Question 18

What are the features of phase 5

Answer 18

aortic valve closes (AorticP>LVP) causing S2 sound, dicrotic notch
Isovolumetic relaxation as all valves closed
Rapid decline in ventricular pressure
End systolic volume of 40ml giving SV of 80ml

Question 19

what are the features of phase 6

Answer 19

Y descent caused by opening of MV (falling AP)
Rapid Ventricular filling (LAP>LVP)
S3 sound in paediatrics, sign of pathology in adults

Question 20

what are features of phase 7

Answer 20

reduced ventricular filling as pressure gradient diminishes 90% full

Question 21

What is the result of abnormal valve function

Answer 21

stenosis- valve doesn’t open enough leading to obstruction to blood flow when normally open

regurgitation- valve doesn’t close fully so back leakage when valve should be closed

Question 22

What are the causes of aortic valve stenosis

Answer 22

degenerative (fibrosis/senile calcification), congenital (bicuspid form of valve), chronic rheumatic fever (inflammation so commissural fusion

Question 23

What occurs as a result of AorValSten

Answer 23

Increased LVP leading to LV hypertrophy, Left sided heart failure leading to angina and syncope.

Question 24

What are the causes of aortic valve regurgitation

Answer 24

aortic root dilation, valvular damage

Question 25

What occurs as a result of AorValRegur

Answer 25

diastolic backflow into LV. increased stroke volume, increased systolic pressure, decreased diastolic pressure, bound pulse and head bobbing, quincke’s sign (nails), LV hypertrophy

Question 26

what are the causes of mitral valve regurgitation

Answer 26

myxomatous degeneration leading to prolapse, damage to papillary muscle after MI, Left sided heart failure causing LV dilation and stretched valve, rheumatic fever so leaflet fibrosis

Question 27

why does mitral valve regurgitation cause LV hypertrophy

Answer 27

backflow into LA increases preload so more blood enters in subsequent cycles

Question 28

What are the causes of mitral valve stenosis

Answer 28

rheumatic fever (99.9% cases). Commissural fusion of valve leaflets

Question 29

what occurs as a resut of MitValSten

Answer 29

LA dilation leading to oesphageal compression and dysphagia or atrial fibrillation and thrombus formation. Increased LA pressure leading to pulmonary oedema, dyspnea (laboured breathing), pulmonary hypertension and consequently RV hypertrophy