THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The SA node starts the sequence by causing the atrial muscles to contract. That’s why doctors sometimes call it the anatomical pacemaker. Next, the signal travels to the AV node, through the bundle of HIS, down the bundle branches, and through the Purkinje fibers, causing the ventricles to contract.

Detailed explanation-2: -Sinoatrial Node The SA node nerve impulses travel through the atria and cause direct muscle cell depolarization and contraction of the atria. The SA node stimulates the right atria directly and stimulates the left atria through the Bachmann’s bundle.

Detailed explanation-3: -The increased firing rate in the SA node increases the heart rate and cardiac output necessary to deliver more oxygen and nutrients to the muscles for the flight-or-fight response.