Question

When the heart pacemaker produces an action potential, the impulse spreads quickly through the atria producing contraction. However, there is a delay before ventricle contraction, why?
a. The ventricles are simply much larger than the atria and take a significantly longer time to contract.
b. The impulse slows down when it passes through the nodal fibers (AV node).
c. The individual nerves controlling the two chambers are inhibiting each other from firing.

Answer 1

Answer: B

Explanation:

The action potential that stimulates heart contraction starts at the Sinoatrial Node (SA Node), then it goes through the nodal fibers, which slow down the action potential impulse, until it reaches the Atrioventricular Node (AV Node or Aschoff-Tawara Node) and then it is transferred to the bundle of His.