Cardiac Cycle

Question 1

What sort of process is the opening and closing of the AV and semilunar valves

Answer 1

PASSIVE - dependent on pressure difference across valve

Question 2

Definition of cardiac cycle

Answer 2

1 complete set of contraction (systole) and relaxation (diastole)

Question 3

DIASTOLE 1

• _____ ventricular relaxation
• valves
• ventricular vol
• change in blood vol
• change in blood flow
• pressure in atria vs ventricle
• beginning of ______ _______

Answer 3

• isovolumetric/isometric ventricular relaxation
• valves are shut
• ventricular volume is at a minimum - ESV (60 ml)
• No change in blood vol
• no change in blood flow
• pressure in atrium < pressure in ventricle initially, then flips as blood is filling atria => AV valves open passively
• beginning of ventricular filling

Question 4

DIASTOLE 2

• how long is ventricular filling
• how much of ventricular filling occurs PASSIVELY down a PRESSURE GRADIENT

Answer 4

• 0.5s at rest

- 80%

Question 5

DIASTOLE 3

• _____ contraction
• what does atrial pressure rise to and what does this result in
• blood vol ejected
• blood vol in ventricle

Answer 5

• atrial contraction
• AP rises to 5 mmHg => P wave on ECG (atrial depolarisation)
• final 20% of blood ejected from atrium -> ventricle
• EDV (130ml)

Question 6

SYSTOLE 1

• _____ ventricular contraction
• what happens to ventricles (3)
• what valve closes
• what valves are already closed
• 1st heart sound
• where is pressure generated

Answer 6

• isovolumetric/isometric ventricular contraction - 0.05s
• ventricles *depolarise - QRS complex on the ECG
• contract
• develop tension
• AV (mitral) valve rapidly closes
• AV and semilunar valves are closed
• closure of AV valves => first heart sound
• pressure is generated in ventricle

Question 7

What is the pressure change for the aortic valve

Answer 7

80 mmHg

Luuuuuuuub dub

Question 8

SYSTOLE 2

• ventricular ______
• LVP >/< AP => what valve opens
• blood vol
• arterial P
• what increases in parallel
• when does 2/3rds of blood ejection occur
• late systole
• what happens to ventricles
• ventricular vol

Answer 8

• ventricular ejection
• LVP > AP so aortic valve opens
• increase in arterial blood vol
• increase in arterial pressure
• LVP and AP increase in parallel, reaching max mid-systole
• 2/3rd of blood ejection occurs in 1st 1/3 ventricular ejection - RAPID
• late systole - reduced ejection - LVP and AP are decreasing
• Ventricles repolarise - T wave on ECG
• Ventricular vol - ESV (60ml)

Question 9

What is longer at rest - systole or diastole

Answer 9

DIASTOLE (2/3)

Systole (1/3)

Question 10

What is diastole composed of

Answer 10

Isovolumetric relaxation - short

Ventricular filling

Question 11

What is systole composed of

Answer 11

Isovolumetric contraction - short

Ventricular ejection

Question 12

DIASTOLE
LVP
A (aortic) P
Arterial pulse pressure (P in systole - P in diastole)

Answer 12

• 0 mmHg
• 80 mmHg
• 40 mmHg

Question 13

SYSTOLE
LVP
A (aortic) P
Arterial pulse pressure (P in systole - P in diastole)

Answer 13

• 120 mmHg
• 120 mmHg
• 40 mmHg

Question 14

EDV

Answer 14

130 ml

Question 15

ESV

Answer 15

60 ml

Question 16

Stroke vol (EDV - ESV)

Answer 16

70 ml

Question 17

RVP in diastole vs systole

Answer 17

0 mmHg (D)
25 mmHg (S)

Question 18

PAP in diastole vs systole

Answer 18

8 mmHg (D)
25 mmHg (S)

Question 19

Duration of cardiac cycle

Answer 19

1 s
=> Diastole = 0.66 s
systole - 0.34 s
EXERCISE - 180 beats/min
D = 0.13 s
S = 0.2 s
As blood flows in almost passively, atria contract almost simultaneously