3.3.4.1 Mass transport in animals

Question 1

The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN). Describe how

Answer 1

• the SAM initiates heart beat (acting like a pace maker)
• and sends impulses across atria causing atria contraction
• AVN delays impulses
• allowing ventricles to fill before they contract
• then AVN sends impulses down Bundle of His / Purkyne fibres
• causing ventricles to contract from base up

Question 2

What is atheroma and how may it cause myocardial infarction?

Answer 2

• atheroma is fatty material
• in the artery wall
• and it is linked to blood clot/thrombosis
• where it can block the coronary artery
• which reduces oxygen/glucose supply to the heart muscle
• which dies as it can no longer respire