Basics

Question 1

What are the 3 factors affecting diffusion?

Answer 1

1. Area
2. Diffusion ‘Resistance’:
3. Concentration Gradient:

Question 2

What is the rate of bloodflow at rest vs during strenuous exercise?

Answer 2

Rest: 5L/min Exercise: can go up to 25L/min

Question 3

How much bloodflow do the following tissues require? a) Brainb) Heartc) kidneys d) skeletal muscle and the gut

Answer 3

Brain/kidneys - high constant flow
Heart - high flow that increases during exercise
Skeletal muscle/gut - high amount post exercise/meal

Question 4

Give 4 descriptive features for a cardiac myocyte

Answer 4

1. Striations
2. 1-2 centrally positioned nuclei
3. Intercalated discs (electrical and mechanical coupling with adjacent cells)
4. Branching

Question 5

What are the 2 types of myocardial cells?

Answer 5

1. Contractile cells (99%)

2. Conducting cells (1%): smaller, fewer myofibrils/filaments (don’t do contractions), similar to neurons

Question 6

Describe the process that occurs after a pacemaker generates one AP

Answer 6

1. SA node (pacemaker cells, rest: 1AP/sec)
2. Short atrial systole (P wave)
3. Excitation reaches AV node: delayed 120 ms
4. Bundle of HIS (rapidly conducted)
5. Purkinje fibres
6. Through ventricular myocardium (endocardial - epicardial)
7. Ventricular systole: 250 ms (ca2+ channels, apex - up)
8. Diastole: 430 ms relaxation, ventricles re-fill

Question 7

Describe the phases of the heart

Answer 7

Isovolumetric contraction: btwn mitral valve closing and aortic opening, NO change in volume, highest O2 consumption

Systolic ejection: aortic valve opens

Isovolumetric relaxation: btwn aortic valve closing and mitral valve opening

Rapid-reduced filling: mitral valve opens (progresses into diastasis - passive filling before atria contract)

Question 8

What generates the four heart sounds?

Answer 8

S1: mitral/tricuspid valves close “lub”
S2: Aortic/pulmonary valves close “dub”
S3: Rapid ventricular filling
S4: “atrial kick”: atrial systole pushes small amount of extra blood into ventricles to limit loss of valve regurg

Question 9

What peaks at the end of systole?

Answer 9

Arterial and interventricular pressure

Question 10

What generates a heart murmur?

Answer 10

Turbulent blood (valve stenosis or incompetence)

Question 11

List two things that can cause aortic stenosis

Answer 11

Bicuspid congenital valve, age-related calcification