Blood circulation in humans

Blood circulation in humans

Pumping of the heart

Initiated and coordinated by the pacemaker [sinoatrial node]

Explain the pumping of the heart. [1]

The sinoatrial node generates electrical impulses.

Explain the pumping of the heart. [2]

Electrical impulses spread rapidly in both atria, causing them to contract at the same time. The contraction of atria helps pump blood into the ventricles.

Explain the pumping of the heart. [3]

The electrical impulses reach the atrioventricular node. The electrical impulses spread through the bundle of His, the Purkinje fibres up to the apex of the heart.

Explain the pumping of the heart. [4]

The electrical impulses spread from the apex of the heart to the whole ventricle wall. The ventricles contract to pump blood out to the lungs and the body.

How is the ‘lub’ sound produced?

The closing of the tricuspid and bicuspid valves.

How is the ‘dub’ sound produced?

The closing of the semilunar valves.

What are the main challenges faced by the pumping of the heart?

The force produced is insufficient, and the blood is forced to flow against gravity.

How is blood flow in the veins assisted?

1. Through the contraction of smooth muscles in the venule and vein walls

2. Through the contraction of skeletal muscles around the veins

How does the contraction of skeletal muscles help with blood flow?

The contraction of skeletal muscles presses and constricts the veins, forcing valves to open and allow blood flow to the heart. The valve is then closed to prevent backflow of blood towards the foot.