Heart

Question 0

Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.

Answer 0

1. Atrium has a higher pressure than ventricle (due to filling/contraction).
2. Atrioventricular valve opens.
3. Ventricle has higher pressure than atrium (due to filling/contraction).
4. Atrioventricular valve closes
5. Ventricle has higher pressure than aorta.
6. Semi-lunar valve opens
7. Higher pressure in aorta than ventricle (as heart relaxes).
8. Semilunar valve closed.
9. (Muscle/atrial/ventricular) contraction causes increase in pressure.

Question 1

Describe how a heart beat is initiated and coordinated

Answer 1

1. SAN sends a wave of impulses across the atria causing ATRIAL CONTRACTION.
2. Non-conducting tissue prevents immediate contraction of ventricles.
3. AVN delays while blood leaves atria/ventricles fill.
4. AVN sends impulses down BUNDLE OF HIS.
5. Impulses cause ventricles to contract from base up.