Track 2: Anatomy/Physiology Conduction System

Question 1

SA node location

Answer 1

Sulcus terminalis at junction between SVC and right atrium on the epicardium

RA free wall surface, posteriorly

Question 2

Bundle of his location

Answer 2

Where aortic leaflets meet tricuspid leaflets, portion of interventricular septum (membranous septum w/o muscle), site of HIS bundle

Question 3

AV node location

Answer 3

Approximate location within the triangle of Koch (center most likely)

Question 4

Triangle of Koch

Answer 4

Tricuspid septal leaflet
Roof of coronary sinus
Attach these 2 points with line that along eustacian ridge

Question 5

Name some of the key characteristics of pacemaker cells

Answer 5

Automaticity
Resting potential is -60 mV
Phase 4 is an upstroke current (pacemaker current)
Longer refractory period (than skeletal muscle and nerves)
Absolute, effective, & relative refractory periods
Atrial refractory period is less than ventricular

Question 6

Describe the PR interval:

What events encompass the PR interval?

Answer 6

Start of P wave (atrial activation) to the start of the QRS (start of ventricular activation)

• Atrial myocardial activation
• AV node activation
• HIS bundle activation
• Bundle branch activation (as bundle branches are activated before ventricular muscle is activated)