Session 2.1

Question 1

What kind of junctions are between cardiac myocytes?

Answer 1

Gap junctions so contract in synchrony

Question 2

Why are cardiac action potentials relatively long?

Answer 2

1 contraction = 1 heartbeat and you want it to be smooooooth

Question 3

What is the purpose of chord tendons??

Answer 3

Anchor valve to stop it inverting

Question 4

Briefly describe the conduction.

Answer 4

1) pacemaker cells in SAN generate an action potential in RA
2) activity spreads over the atria = atrial systole
3) reaches the atrioventricular node and delayed for 120ms
4) from a-v node excitation passes though septum between ventricles
5) then spreads through ventricular myocardium from inner endocardial to outer epicardial surface.
6) ventricles contract from atria upwards

Question 5

What are the 7 phases of the cardiac cycle and which bits are systole And which are Diastole?

Answer 5

1) atrial contraction
2) isovolumetric contraction
3) rapid ejection
4) reduced ejection
5) isovolumetric relaxation
6) rapid filling
7) reduced filing

Stages 2-4 are systole, rest are diastole.

Question 6

What happens to Systole and diastole when heart rate gets faster respectively ?

Answer 6

Systole stays the same, diastole gets shorter.

Question 7

What side of the heart are wiggers diagrams plotted for?

Answer 7

The left side

The right side would be the same sort of diagram but at lower pressure

Question 8

What is the name given to the maximum ventricular volume?

Answer 8

The end diastolic volume (EDV). Get at the end of phase 1 (atrial contraction) of the cardiac cycle

Question 9

How would you work out stroke volume?

Answer 9

End diastolic volume - end systolic volume = stroke volume

Question 10

How can you get stenosis?

Answer 10

Valve doesn’t open enough = get obstruction to blood flow = stenosis

This could be

• degenerative.
• congenital
• a result of infection

Question 11

How can you get regurgitation?

Answer 11

Valve doesn’t close all the way = back leakage when valve should be closed.

Question 12

Where are defect valves most commonly found?

Answer 12

The left side - mitral and aortic valve.

Question 13

What are the consequences of aortic valve stenosis?

Answer 13

• increased LV pressure = less ventricular hypertrophy

- left sided heart failure = syncope (faint as lack of blood to brain), angina (less o2 supplied to heart)

Question 14

What are the causes of aortic valve regurgitation?

Answer 14

• aortic root dilation (leaflets pulled apart)
• vlavular damage (endocarditis rheumatic fever)
• blood flows back into LV during diastole
• increase stroke volume
• systolic pressure increases
• diastolic pressure decreases
• LV hypertrophy
• bounding pulse (quinkes sign = beds of nails flush with colour in synchrony with heart)

Question 15

What causes mitral valve regurgitation?

Answer 15

• damage to papillary muscles after heart attack
• left sided heart failure leads to LV dilation which can stretch valve
• rheumatic fever can lea to leaflet fibrosis which disrupts seal formation
• as some blood leaks back into LA, this increases preload as more blood enters LV in subsequent cycles = can LV hypertrophy.

Question 16

What is rheumatic fever?

Answer 16

Fusion of the leaflets

Question 17

What causes mitral valve stenosis and what are the consequences?

Answer 17

Rheumatic fever
Causes increased LA pressure
= pulmonary oedema, dypnea and pulmonary hypertension = RV hypertrophy

Also LA dilation = atrial fibrillation (and thrombus formation) as well as oesophagus compression so get dysphagia

Question 18

What is the definition of afterload and preload?

Answer 18

Afterload - the load the heart must eject blood supply against
Preload - amount the ventricles are stretched during diastole

Question 19

What is the total peripheral resistance?

Answer 19

Resistance to blood flow offered by all systematicc vasculature