Anatomy and Function of the Heart

Question 1

Name the layers of the heart wall (from outer to inner)

Answer 1

Pericardium
Epicardium
Myocardium
Endocardium

Question 2

What type of valves separate the chambers?

Name those valves

Answer 2

Atrioventricular
Tricuspid
Mitral/bicuspid

Question 3

What type of valves are after the ventricles?

Name those valves

Answer 3

Semilunar
Pulmonary
Aortic

Question 4

What attaches the cusps of valves to the heart muscle?

Answer 4

Tendinous chords

Question 5

Describe the electrical pathway of heart contractions

Answer 5

Sinoatrial node (SA node)
Atrioventricular node (AV node)
AV bundle/bundle of His
Bundle branches
Purkinje fibres

Question 6

Name the 2 types of cardiomyocytes

Answer 6

Pacemaker (autorhythmic)

Contractile cells

Question 7

How are action potentials passed from one cardiomyocyte to another

Answer 7

Via gap junctions

Question 8

Describe action potentials in pacemaker cells

Answer 8

1) FUNNY channels open when membrane potential < -40mV
2) Slow influx of Na+
3) FUNNY channels close just short of the threshold (-40mV)
4) Ca channels open
5) Rapid influx of Ca++
6) At peak, K channels open + Can channels close
7) K+ leaves cell
8) voltage returns to normal

Question 9

Describe action potentials in contractile cells

Answer 9

1) Na+ and Ca++ move in (brings threshold up to -70mV)
2) At -70mV, FAST Na channels open -> Rapid influx of Na+
3) At -40mV, SLOW Ca channels open -> Slow influx of Ca++
4) At peak, FAST Na channels close and voltage gated K channels open -> small decrease in membrane potential
5) K+ efflux eventually balanced by Ca++ influx -> stable potential for 200ms
- Ca++ obtained from sarcoplasmic reticulum for contraction
6) Ca++ slowly close -> K+ efflux results in repolarisation
7) Ca++ actively transported out and back into sarcoplasmic reticulum

Question 10

What does the P wave represent in the cardiac cycle?

Answer 10

Atrial systole

Question 11

What does the PR interval represent in the cardiac cycle?

Answer 11

Electrical signal travelling from sinus node to ventricles

Question 12

What does the QRS wave complex represent in the cardiac cycle?

Answer 12

Ventricular depolarisation + systole

Question 13

What does the ST segment represent in the cardiac cycle?

Answer 13

Interval between ventricular depolarisation + repolarisation

Question 14

What does the T wave represent in the cardiac cycle?

Answer 14

Repolarisation of ventricles

Question 15

What are the 2 categories of factors for heart rate?

Answer 15

Parasympathetic

Sympathetic

Question 16

Which part of the nervous system causes tachycardia?

Answer 16

Sympathetic

Question 17

Which part of the nervous system causes bradycardia?

Answer 17

Parasympathetic