The Heart As A Pump

Question 1

What type of vessels are found in the arterial blood supply? Why?

Answer 1

Resistant vessels

Restrict blood flow to drive supply to hard to perfused areas of body

Question 2

What type of vessels are found in the venous blood supply? Why?

Answer 2

Capacitance vessels

Enable system to vary amount of blood pumped around body

Question 3

What are the valves of the heart?

Answer 3

Tricuspid (RA to RV)
3

Semilunar/pulmonary (RV to P)
2

Mitral (biscuspid) (LA to LV)
3

Semilunar/aortic (LV to A)
3 (1-2%- congenital defect=2 cusps)

Question 4

What is systole?

Answer 4

Contraction and ejection of blood from ventricles

Question 5

What is diastole?

Answer 5

Relaxation and filling of ventricles

Question 6

What is the stroke volume?

Answer 6

Volume of blood pumped out by heart with every beat (~70ml)

Question 7

What is the approx volume of blood in the body?

Answer 7

5 litres (70 ml x 70bpm=4.9 litres per minute)

Question 8

List some features of heart muscle (6)

Answer 8

• striated
• discrete cells but interconnected electrically (intercalated discs)-functional syncytium
• formed of cardiomyocytes/myocardiocytes
• single nucleus
• branched structure
• have diads (1 T tubule+terminal cisterna of SR)

Question 9

How long is the average cardiac action potential?

Answer 9

~280 ms

Question 10

What structures prevent the valves inverting during systole?

Answer 10

Chordae tendineae attach to the valves and are held in place by the papillary muscles

Question 11

How long does the AV node delay the action potential in the heart?

Answer 11

~120ms

Question 12

After the action potential in the heart has spread down the septum between the ventricles, how does it spread through the ventricular myocardium?

Answer 12

From endocardial to epicardial

In to out

Question 13

List the 7 phases of the cardiac cycle

What stages are systole and which are diastole?

Answer 13

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

(2-4)systole
(5-1) diastole

Question 14

During exercise what part of the heart cycle reduces to allow the heart to pump faster?

Answer 14

Diastole

Question 15

Which side of the heart is more susceptible to abnormal valve function

Answer 15

The left valves (mitral and aortic)

Question 16

What are the two main types of valve abnormalities? Explain them

Answer 16

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

Regurgitation (incompetence/insufficiency)-valve doesn’t close all the way-back leakage when valve should be closed

Question 17

Describe Aortic valve regurgitation: causes, impact and sounds

Answer 17

Causes:

• Aortic root dilation (leaflets pulled apart)
• valvular damage (endocarditis rheumatic fever)

Impact:

• blood flow back into LV during diastole
• increase stoke volume
• systolic pressure increases
• diastolic pressure decreases (because we lose blood in the aorta)
• bounding pulse (quincke’s sign)
• LV hypertrophy

Sound:
Early decrescendo diastolic murmur (lub, dub, whoosh)

Question 18

Describe mitral valve regurgitation: causes, impact and sounds

Answer 18

Causes:

• myxomatous degeneration weakens the tissue leading to prolapse
• damage to papillary muscle after heart attack
• Lsided heart Failure=LV dilation which can stretch valve
• rheumatic fever can lead to leaflet fibrosis which disrupts seal formation

Impact:
Blood leaks back into LA, increases preload as more blood enters LV in subsequent cycles…can cause LV hypertrophy

Sound:
Holosystolic murmur (lub, whoosh-no change in intensity, dub)

Question 19

Describe Aortic valve stenosis: causes, impact and sounds

Answer 19

Cause:

• degenerative (senile calcification/fibrosis)
• congenital (bicuspid form of valve)
• chronic rheumatic fever-inflammation-commissary fusion

Impact:

• less blood through valve
• increase LV pressure- hypertrophy
• Lsided heart failure (reduced blood supply)-syncope (in NS)/angina (in heart)
• microangiopathic haemolytic anaemia (shear stress as blood is forced through and RBCs are damaged)

Sound:
Crescendo-decrescendo murmur (lub-whoosh-dub)

Question 20

Describe mitral valve stenosis: causes, impact and sounds

Answer 20

Causes:

• rheumatic fever (99.9% of cases)- consequence of severe strep throat
• commissary fusion of valve leaflets

Impact:

• Increased LA pressure
• pulmonary oedema, dyspnea, pulmonary hypertension= RV hypertrophy
• LA dilation= atrial fibrillation and thrombus formation/ oesophagus compression and dysphagia (difficulty swallowing)