The av node is the secondary pacemaker of the heart with a rate of 40 to 60 beats per minute.
a. true
b. false

True

Explanation:

At 40-60 beats per minute the cells of Artrioventicular node normally discharge and at this rate it is known as secondary pacemaker.

The electrical conducting system after this secondary pacemaker is known as Bundle of His. The right and left branches along with the Purkinje Fibres will produce action potential at the rate of 30 to 40 per minutes.

The failure of SA and AV node both fails then the cells becomes pacemaker.

5. method

15. communicate, transport

18. component

21. learn

22. preceding

23. display

24. area

25. anomalous, unusual, unconventional

answer:

it could come from a variety of sources.

explanation:

..although it was most likely developed through zoonotic transmission, where an infectious disease which usually afflicts when animals jump to humans.