Question 18M.3.HL.TZ1.21
| Date | May 2018 | Marks available | [Maximum mark: 7] | Reference code | 18M.3.HL.TZ1.21 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Comment, Explain, Outline, Suggest | Question number | 21 | Adapted from | N/A |
Outline the role of the sinoatrial node in the contraction of the heart.
[2]
a. initiates action potentials / electrical impulses (at start of cardiac cycle)
b. acts as pacemaker/ continuous beating without external stimuli
c. signal spreads over atria / causes contraction of atria (systole)
d. impulses transmitted to AV (atrioventricular) node / cannot pass directly to ventricles
The graph shows the results of a study of the incidence of coronary heart disease (CHD) in different age groups of men participating in a study carried out by the National Heart, Blood and Lung Institute.
Comment on the claim that the bar chart proves that old age causes CHD.
[1]
a. data show correlation (increased chance of CHD with age) not causation
OWTTE.
Suggest one factor other than age and hypertension that is correlated with the incidence of CHD.
[1]
sex / ethnic group / genetics / obesity / diet / life style / medical history / high cholesterol levels
Smoking / stress go under lifestyle.
Hypertension has been suggested as a possible cause of CHD. Explain the possible causes of hypertension.
[3]
a. deposition of fat in arteries thus losing elasticity/forming fibrous tissues
b. deposition of fat/formation of plaque in arteries thus narrowing of lumen/causing a blockage
c. high salt levels in diets thus retaining more fluids
d. smoking because nicotine is a vasoconstrictor molecule
e. prolonged high levels of stress thus causing vasoconstriction / exposure to stress hormones
f. genetic predisposition makes it more likely that other factors will lead to hypertension
Do not accept a list.