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Question 1

23. Name two major branches of the right coronary artery.

Answer 1

Marginal arteries

Post 4 artery

Question 2

24. Name two major branches of the left coronary artery

Answer 2

Circumflex artery

Ant 4 artery

Question 3

25. What does an EKG represent?

Answer 3

Electrical activity in the heart

Question 4

26. Name the two groups of pacemaker cells

Answer 4

SA node

AV node

Question 5

27. Describe the general root of the heart’s conduction system.

Answer 5

The conducting system of the heart consists of cardiac muscle cells and conducting fibers (not nervous tissue) that are specialized for initiating impulses and conducting them rapidly through the heart. They initiate the normal cardiac cycle and coordinate the contractions of cardiac chambers. Both atria contract together, as do the ventricles, but atrial contraction occurs first.

Question 6

28. Why doesn’t atrial conduction spread passively to ventricular tissues?

Answer 6

The atria contracts first then the ventricles contract.

Question 7

29. Define a cardiac cycle

Answer 7

•A cardiac cycle is the period from the start of one heartbeat to the start of the next.

Question 8

30. What is the function of the moderator band

Answer 8

Prepares papillary muscles for contraction

Question 9

How long do heartbeats last?

Answer 9

• Each heartbeat lasts about 0.37 seconds

* At rest, there is a pause of about 0.5 sec between each heartbeat and 72 beats per minute.

Question 10

What is the purpose of the sympathetic and parasympathetic?

Answer 10

Sympathetic- Increases heart rate cardioacceleratory center- (CAC)

Parasympathetic- relaxes heart rate cardioinhibitory center- (CIC)

Question 11

31. What are the terms that describe the self-initiating nature of the cardiac cycle?

Answer 11

Automaticity

Question 12

32. What group of pacemaker cells initiate atrial contraction

Answer 12

SA node

Question 13

33. In what direction does excitation spread from that atrial pacemaker?

Answer 13

Spreads down walls of atrium to the AV node and laterally to the left atrium

• Impulses leave AV Node and travel down left and right bundle branches toward apex of the heart
• Branches diverge and become Purkinje fibers which stimulate deep into myocardium of both ventricles.
• Moderator band delivers impulses to papillary muscles of ventricles, allowing contraction of those papillary muscles just prior to contraction of the ventricles. Why is this important?
• Since Purkinje fibers radiate from apex toward the base of the heart, myocardial tissue contracts similarly, pushing blood toward the semilunar valves and allowing a directed propulsion toward pulmonary and aortic trunks.

Question 14

34. Where is the AV node located?

Answer 14

Floor of right atrium

Question 15

35. Name three insurance policies that prevent the ventricular contraction rate from mimicking atrial fibrillation.

Answer 15

546

Question 16

36. What is the synaptic delay for an impulse to pass through the AV node?

Answer 16

100-120 milliseconds

Question 17

37. Which segment of the conduction system excites cardiac myocytes of the ventricles?

Answer 17

Cengi fibers

Question 18

38. Which wave of the EKG represents ventricular depolarization?

Answer 18

QRS complex

Question 19

When does ventricular contraction actually start?

Answer 19

At the R peak

Question 20

39.What does the P wave of an EKG represent?

Answer 20

Atrial depolarization

Question 21

40. What is the usefulness of an EKG?

Answer 21

Can be used to measure heart contractions

Question 22

41. What would abnormally long intervals within an EKG represent?

Answer 22

A slowed relaxed heart rate or a damaged heart