Anatomy of the Heart

Question 1

What two chambers are separated by the mitral valve? The tricuspid valve?

Answer 1

Left Atrium/Ventricle; Right Atrium/Ventricle

Question 2

What are the 5 layers of the heart from outside to inside (starting with the pericardium)?

Answer 2

Parietal Pericardia, Visceral Pericardia, Epicardium, Myocardium, Endocardium

Question 3

How many nuclei are in a myocyte? What are myocytes separated by?

Answer 3

1; Intercalated disks

Question 4

What are the main players in the thin filaments within a myocardial sarcomere?

Answer 4

Alpha - tropomyosin-1 and troponin complex (troponins I, C, and T)

Question 5

What is the ideal sarcomere length that allows for maximal contraction?

Answer 5

2-2.2 um

Question 6

What initiates contraction of cardiac muscle?

Answer 6

Increases in cytosolic free calcium

Question 7

Describe the process of cardiac myocyte contraction

Answer 7

1. AP down T tubules which allows Ca influx thru L-type Calcium channel
2. Ca entering cells causes Ca induced Ca release via Ryanodine receptor (RyR2)
3. Change of conformation of troponin allowing for crossbridging with myosin

Question 8

What is the relationship between force and Ca in the cell?

Answer 8

Force is proportional to [Ca]

Question 9

Is myocardial relaxation an active or passive process? Why?

Answer 9

Active; Requires ATP to pump Ca out of the cell

Question 10

What are the two major functions of cardiomyocytes?

Answer 10

1. Initiate heartbeats by generating electric current through their automatic rhythmicity
2. Distribute electric current to activate atrial and ventricular myocardium

Question 11

What is the general rule about heart pacemaker?

Answer 11

The more distal the pacemaker site, the slower the heart rate

Question 12

What is the connection betwixt the atria and the ventricles?

Answer 12

Bundle of His

Question 13

What does the Left anterior descending coronary artery supply?

Answer 13

Anterior left ventricle, Adjacent anterior right ventricle, anterior half to two thords of the interventricular septum

Question 14

What does the left circumflex coronary artery supply?

Answer 14

Lateral wall of the left ventricle

Question 15

What does the right coronary artery supply?

Answer 15

Bulk of the right ventricle, posteroseptal left ventricle and posterior third to half of the interventricular septum at base of heart

Question 16

What determines “sided-ness” of a heart? Which type is dominant?

Answer 16

Which artery supplies the most blood to the posterior descending coronary artery; Right, 5-10% Left (Left circumflex supplies the posterior descending coronary artery)

Question 17

What part of the heart is most susceptible to ischemia? Why? What is the general rule about myocardial blood flow?

Answer 17

The endocardium because as a general rule, blood flow in the myocardium occurs inward from epicardium to the endocardium.