Heart

Question 1

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

Answer 1

1. SAN initiates heartbeat / acts as a pacemaker / myogenic;2. (SAN) sends wave of electrical activity / impulses (across atria) causing atrial contraction;3. AVN delays (electrical activity / impulses);4. (Allowing) atria to empty before ventricles contract / ventricles to fill before they contract;5. (AVN) sends wave of electrical activity / impulses down Bundle of His / Purkyne fibres;6. (Causing) ventricles to contract (from base up) / ventricular systole;

Question 2

What is atheroma and how may it cause myocardial infarction? (5)

Answer 2

1. Cholesterol / plaque / lipoprotein / LDL / fatty material / cells2. In artery wall / under lining / endothelium of artery / blood vessel;3. Atheroma linked to blood clot / thrombosis;4. (Blocks) coronary artery / artery supplying heart muscle / tissue / cells;5. Reduces oxygen / glucose supply (to heart muscle / tissues / cells);6. (Heart muscle / tissue / cells) unable to respire / dies;

Question 3

Explain, in terms of pressure, why the semilunar valves open.

Answer 3

Pressure is greater below valve / in ventricle than (artery)

Question 4

When a wave of electrical activity reaches the AVN, there is a short delay before a new wave leaves the AVN. Explain the importance of this short delay

Answer 4

Allow atria to empty / contract / ventricles to fill; Before ventricles contract

Question 5

Omega-3 fatty acids are unsaturated. What is an unsaturated fatty acid?

Answer 5

Double bond(s);(Bonds) between carbon

Question 6

The maximum pressure in the ventricle is much higher than that in the atrium. Explain what causes this.

Answer 6

1. (Ventricle has) thick wall / more muscle2. So contractions are stronger / harder

Question 7

The human heart has four chambers.In which one of the four chambers of the human heart does pressure reach the highest value?

Answer 7

Left ventricle

Question 8

Explain how the structure of this chamber causes this high pressure.

Answer 8

Thick muscle or thick walls

Question 9

Aspirin may reduce the risk of myocardial infarction . Explain how.

Answer 9

1. Prevents/reduces formation of thromboxane2. Blood clots do not form / less likely to form3. (Do not block) coronary arteries / vessels4. Heart muscle/wall gets oxygen

Question 10

The heart controls and coordinates the regular contraction of the atria and ventricles. Describe how

Answer 10

1. SAN → AVN → bundle of His /Purkyne fibres2. Impulses / electrical activity (over atria)3. Atria contract4. Non-conducting tissue (between atria and ventricles)5. Delay (at AVN) ensures atria empty/ ventricles fill before ventricles contract6. Ventricles contract from apex upwards

Question 11

The diet of a person can increase the risk of coronary heart disease. Explain how.

Answer 11

1. Too much saturated fat/ cholesterol in diet2. Increase in LDL/ cholesterol in blood3. Atheroma/ fatty deposits/ plaques in artery walls4. Reduces diameter of / blocks coronary arteries5. Less oxygen/ glucose to heart muscle /tissue/ cells6. Increase in blood pressure7. (Increased risk of )clot / thrombosis / embolism/ aneurysm

Question 12

The pulse felt in the artery in the wrist can be recorded and used to measure heart rate.Suggest why the pulse felt can be used to measure heart rate

Answer 12

1. Caused by pressure/surge of blood2. From (one) contraction/beat of (left) ventricle/heart;

Question 13

Atheroma formation increases a person’s risk of dying. Explain how.

Answer 13

1. Atheroma is fatty material/cholesterol/foam cells/plaque/calcium deposits/LDL2. In wall of artery3. (Higher risk of) aneurysm/described4. (Higher risk of) thrombus formation/blood clot5. Blocks coronary artery6. Less oxygen/glucose to heart muscle/cells/tissue7. Reduces/prevents respiration8. Causing myocardial infarction/heart attack9. Blocks artery to brain10. Causes stroke/stroke described

Question 14

Describe how a heartbeat is initiated and coordinated

Answer 14

1. SAN sends wave of electrical activity / impulses (across atria) causing atrial contraction2. Non-conducting tissue prevents immediate contraction of ventricles/prevents impulses reaching the ventricles3. AVN delays (impulse) whilst blood leaves atria/ventricles fill4. (AVN) sends wave of electrical activity / impulses down Bundle of His5. Causing ventricles to contract from base up

Question 15

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

Answer 15

1. Atrium has higher pressure than ventricle (due to filling/contraction)2. Atrioventricular valve opens3. Ventricle has higher pressure than atrium (due to filling/contraction)4. Atrioventricular valve closes5. Ventricle has higher pressure than aorta6. Semilunar valve opens7. Higher pressure in aorta than ventricle (as heart relaxes);8. Semilunar valve closes9. (Muscle/atrial/ventricular) contraction causes increase in pressure

Question 16

Arteries and arterioles take blood away from the heart.Explain how the structures of the walls of arteries and arterioles are related to their functions (6).

Answer 16

Elastic tissue1 Elastic tissue stretches under pressure/when heart beats2 Recoils/springs back3 Evens out pressure/flowMuscle4 Muscle contracts5 Reduces diameter of lumen/vasoconstriction/constricts vessel6 Changes flow/pressureEpithelium7 Epithelium smooth8 Reduces friction/blood clots/less resistance