Cardiac cycle

Question 1

What proportion of the heart beat does systole and diastole take up and how many phases comprise each?

Answer 1

Diastole-4 phases-Lasts 2/3 of each beat

Systole-3 phases-Lasts 1/3 of each beat

Question 2

List the 7 phases of a heartbeat

Answer 2

Isovolumetric contraction
Rapid ejection
Slow ejection

Isovolumetric relaxation
Rapid passive filing
Slow passive filling
Atrial systole

Question 3

How do you calculate ejection fraction?

Answer 3

Stroke volume/End diastolic volume

Question 4

What heart sound will you hear with congestive heart failure, pulmonary embolism or tricuspid incompetence?

Answer 4

4th heart sound

Question 5

What makes the 1st heart sound? (lub)

Answer 5

AV valves closing

Question 6

What phase marks the end of systole?

Answer 6

Reduced ejection

Question 7

What causes the t-wave on an ECG

Answer 7

Repolarisation of the ventricular muscle

Question 8

What causes the QRS complex on an ECG

Answer 8

Ventricular muscle contraction

Question 9

What causes the p-wave on an ECG

Answer 9

Atrial contraction

Question 9

What occurs under isovolumetric contraction?

Answer 9

The ventricular muscles contract isometrically(muscle contracts but fibres stay the same length), applying pressure on the blood but not ejecting it

Question 10

What is the pressure in the pulmonary circuit and how does the pressure pattern vary with the pattern on the left side of the heart?

Answer 10

25/5mmHg

-Identical pressure pattern, just lower on the right side

Question 11

At what point on a pressure volume loop do the ventricles encounter afterload?

Answer 11

Right as the ventricles begin to contract in ejection(SL valves open
(Top right on this diagram)

Question 12

What is ESPVR?

Answer 12

ESPVR: End systolic pressure-volume relationship

ESPVR is the maximal pressure that can be developed by the ventricle at any given volume

Question 13

What is the relationship between increased preload causing increased stroke volume?

Answer 13

Frank-Starling relationship

Question 14

How does increased preload affect stroke volume loops?

Answer 14

Stroke volume increases(FSR)
Loop widens to the right

Question 15

How does increased afterload affect a stroke volume loop

Answer 15

Stroke volume decreases
Loop narrows to the right(Left edge moves right) and gets taller by proxy(ESPVR)
(Greater pressure required to open aortic valve)

Question 16

What increases heart contractility and what is the mechanism?

Answer 16

Contractility: Strength of heart contraction

Sympathetic stimulation-Causes increased delivery of Ca2+ to myofilaments(Ionotropy)

Question 17

What feature controls the ESPVR line in a PV loop?

Answer 17

Heart muscle contractility

Question 18

How does noradrenaline/adrenaline affect heart muscle contractility?

Answer 18

Nor/adrenaline activates a g-protein coupled receptor, activating the protein kinase pathway which phosphorylates the
L-type Ca2+ channel,
SR Ca2+ release channel
SR Ca2+ ATPase
which increases delivery of Ca2+ to myofilaments and increases contractility

Question 19

What causes the 2nd heart sound(dub)

Answer 19

Closure of the pulmonary/aortic valves

Question 20

What is and what causes the dichrotic notch on an aorta pressure chart

Answer 20

Aortic valve closure - rebound pressure as distended aortic wall relaxes

Question 21

What causes the 3rd heart sound?

Answer 21

May signify turbulent ventricular filling
Can be due to severe hypertension or mitral incompetence

Question 22

When do the ventricles encounter preload?

Answer 22

When the ventricles start to be filled with blood by the atria

Question 23

Give the ways a pressure volume loop changes during exercise

Answer 23

-The loop expands in width due to increased metabolic demand
-ESPVR line steepens due to sympathetic activation
-Loop gets taller, due to increased pressure(caused by contractility)

Question 24

Why does afterload increase during exercise?

Answer 24

Increased arterial pressure means the ventricles have o generate higher pressures to open the semi-lunar valves

Question 25

What is the longest phase of the cardiac cycle

Answer 25

Reduced passive filling