The paper speed of an electrocardiographic machine should be set ...

[ss2343]

The paper speed of an electrocardiographi c machine should be set at a speed of ____ mm/s.
 
  a. 10 c. 20
  b. 15 d. 25

Question 2

Automatic electrical discharges in the myocardium normally begin within which of the follow-ing?
 
  a. Bundle of His c. Bachmann's bundle
  b. Sinoatrial node d. Atrioventricular node

[pratush dev]

Answer to Question 1

ANS: D
When an ECG is recorded, the paper speed is set at 25 mm/s, the equivalent of 1500 mm/min.

Answer to Question 2

ANS: B
The sinoatrial node , as well as the atrioventricular node, normally have action potentials that differ from those of other excitable cells of the heart. Depolarization of the sinoatrial node initi-ates the heartbeat by triggering a wave of excitation that spreads through the right and left atria as it moves toward the atrioventricular node.