The atrioventricular node delays the impulse so that

  1. the SAN can recover
  2. the atria finish contracting before the ventricles contract
  3. blood flows back into the atria
  4. the ventricles contract first
Answer

B) the atria finish contracting before the ventricles contract

The delay lets ventricles fill. AS & A Level Biology · Topic 8 Transport in Mammals · 8.3 The heart

Biology MCQ · More A Level Biology: Transport in mammals MCQs · Practise