S2L1 - The Heart as a Pump

Question 1

What is the period when the ventricles contract called?

Answer 1

Systole

Question 2

What is the period when the ventricles relax called?

Answer 2

Diastole

Question 3

What is myocardium and what does it consist of?

Answer 3

Myocardium is the muscular tissue of the heart and is the middle of three layers forming the heart wall. It consists of individual cells joined bhy low electrical resistance connections.

Question 4

Define heart rate:

Answer 4

Heart rate = beats per minute

Question 5

Define stroke volume:

Answer 5

Stroke volume - volume of blood (ml) ejected per heart beat

Question 6

Define cardiac output:

Answer 6

Cardiac output (ml/min) = heart rate x stroke volume.

Question 7

What stages of the Wigger’s diagram do the letters a to g correspond to?

Answer 7

a = atrial contraction
b = isovulumic contraction
c = rapid ejection
d = reduced ejection
e = isovulumic relaxation
f = rapid ventricle filling
g = slow ventricle filling

Question 8

What are the four normal heart sounds?

Answer 8

S1 = Mitral (and tricuspid) closure ('lub')
S2 = Aortic and pulmonary valve closure ('dub')
S3 = Passive LV filling - early diastole (not always heard)
S4 = Active (atrial kick) LV filling - late diastole (not always heard)

Question 9

What is the significance of the JVP?

Answer 9

The JVP is normally a double pulse with each beat, but with atrial fibrilation or a leaking tricuspid valve there is only one pulse.

Question 10

Mitral stenosis: where is it heard, what does it sound like and what causes it?

Answer 10

Heard at the apex
Low pitched mid-diastolic rumble
Rheumatic fever; also uncommonly calsification of leaflets and congenital stenosis.

Question 11

Mitral Regurgitation: where is it heard, what does it sound like and what causes it?

Answer 11

Heard at the apex
High-pitched blowing, holosystolic murmur
Most common cause is endocarditis (s.aureus); rhumatic heart disease; annulus/chordae tendinae/papillary muscle pathology
most common form of valvular heart disease

Question 12

Aortic stenosis: where is it heard, what does it sound like and what causes it?

Answer 12

Heard in the right upper sternal boarder, second intercostal space.
Harsh systolic, cresendo-decresendo murmur.
Calcification of the aortic valve (>50% age related; 30-40% congenital); 10% accute rheumatic fever.

Question 13

Aortic regurgitation/insufficiency: where is it heard, what does it sound like and what causes it?

Answer 13

Heard left upper sternal boarder while patient is seated, leaning forward and on expiration.
Early diastolic decresendo murmur.
50% caused by aortic root dilation; also innate bicuspidal aortic valve and retraction of the cusps due to endocarditis/RF.

Question 14

What receptors do catecholamines (eg. adrenaline) act on? What affect do they have on the heart and how does this come about?

Answer 14

Catecholamines act on beta-receptors, mainly beta-1. They increase contractility (inotropic) and heart rate (chronotropic) by increasing intracellular calcium ions.

Question 15

What two types of hypertrophy are there, and what causes each?

Answer 15

Concentric - caused by pressure overload;

Eccentric - caused by volume overload.