The Beating Heart

Question 1

Sinoatrial node (SA)

Answer 1

Stimulates the muscle cells to contract and relax rythmatically, found in the walls of the right atrium

Question 2

Contraction of the heart

Answer 2

1. An electrical signal spreads over the two atria and makes them contract simultaneously
2. Once the atria contract, the signal reaches the Atrioventricular (AV) node
3. The AV node transmits a signal through the bundle of specialized fibres called the bundle of his
4. Fibres relay the signal through two branches called the Purkinje fibres
5. Which stimulates an almost simultaneous contraction of the ventricles

Question 3

ECG

Answer 3

Change in voltage by electrical signal

P- Atria contract
Q- ventricular excitation in the heart apex and valves close
R/S- ventricles finish contracting
T- Ventricles relax and the valves close

A heart murmur is made when there are problems closing the valves