| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.HL.TZ2.19 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Distinguish | Question number | 19 | Adapted from | N/A |
Question
In control subjects, blood potassium levels are maintained, through homeostasis,between 3.5 and 4.5 mmol litre–1. In patients with anorexia, blood potassium canfall below this level. This is known as hypokalemia. In patients with kidney failure, levels can rise above this range, causing hyperkalemia. The traces show the electrocardiograms (ECGs) of a patient with hypokalemia, a normal subject and a patient with hyperkalemia.
Distinguish between the ECG trace of the patient with hypokalemia and the patient with hyperkalemia.
Outline the events that occur within the heart that correspond to the QRS complex.
Severe hypokalemia can lead to ventricular fibrillation. Describe the medical response to ventricular fibrillation.
Sometimes hyperkalemia occurs as a body tries to respond to low blood pH. State the normal range of blood pH in the human body.
Explain how low blood pH causes hyperventilation (rapid breathing).
Markscheme
a. hypokalemia has a flat T-wave whereas hyperkalemia has a heightened T-wave OWTTE
OR
hypokalemia S-T interval longer Accept vice versa
b. hypokalemia has narrower/faster QRS complex compared to hyperkalemia Accept vice versa
c. hypokalemia trace/baseline «overall» lower than hyperkalemia Accept vice versa
a. arrival of signal at AV node
b. transmission via conducting fibres/bundle of His/Purkinje fibres
c. ventricles depolarize
d. atrioventricular valves close
OR
semilunar valves open
e. ventricular systole/contraction
f. contraction begins at apex/base
a. use a defibrillator
b. place electrodes on exposed chest of victim
c. in a line with the heart in the middle of a diagonal line between the two paddles
d. the device determines whether fibrillation is happening
e. if it is, an electric discharge is given off to restore a normal heart rhythm
around 7.4 or 7.35 to 7.45
a. increased CO2 lowers blood pH
b. chemoreceptors in carotid/aorta detect lower pH
c. signal/impulses to medulla «oblongata»
OR
signal/impulses to respiratory centre
d. «from medulla/respiratory centre» to intercostal muscles/diaphragm
e. ventilation rate increase occurs to expel CO2
Examiners report
Syllabus sections
- 22M.1.HL.TZ1.40: What is the role of HCG in early pregnancy? A. It prevents the degeneration of the corpus...
- 18M.3.HL.TZ2.22a: Outline one method that the researchers could have used to measure heart rate in this study.
- 16N.3.HL.TZ0.22c: Explain why the QRS wave has a larger amplitude than a P wave.
- 18M.3.HL.TZ2.22c: Outline the use of defibrillation to treat life-threatening cardiac conditions.
- 18M.3.HL.TZ1.21b.ii: Suggest one factor other than age and hypertension that is correlated with the incidence of CHD.
- 18M.3.HL.TZ2.22b: Suggest reasons for the change in maximum heart rate with increasing age.
-
20N.3.HL.TZ0.22a:
Evaluate the effect of salt on blood pressure using the data in the graph.
- 19N.3.HL.TZ0.21b: Outline the use of a defibrillator.
-
19M.3.SL.TZ1.16b:
The micrograph shows cardiac muscle.
[Source: https://commons.wikimedia.org/wiki/File:Musculocardiaco.jpg by Goyitrina,
licensed Creative Commons Attribution-Share Alike 3.0]The structure labelled X in the micrograph is a junction between two cardiac muscle cells. Identify the structure labelled X.
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17M.3.SL.TZ2.21a:
The diagram shows the use of a sphygmomanometer in the measurement of blood pressure.
Identify the systolic pressure and diastolic pressure for this adult male.
Systolic pressure (mm Hg):
Diastolic pressure (mm Hg):
-
17N.3.SL.TZ0.16c:
Outline reasons for fitting an artificial cardiac pacemaker.
- 17M.3.SL.TZ1.20c: Outline the use of artificial pacemakers for patients with a heart condition.
-
18M.3.SL.TZ1.16a:
Compare and contrast the data for the two time periods.
- 17M.1.SL.TZ1.10: The graph shows the effect of increasing the substrate concentration on the rate of an...
- 18N.3.SL.TZ0.17a: State how many normal heartbeats are shown in the ECGs.
- 18N.3.SL.TZ0.17b: Outline how a defibrillator is used to restore normal heartbeat.
- 17N.3.SL.TZ0.16b: Explain the events that cause the sound shown on the phonocardiogram at the start of systole.
- 18M.3.SL.TZ1.16b: Using the data, evaluate the claim that patients with diabetes have a higher risk of...
- 16N.3.SL.TZ0.15a: Outline the reasons that the female patients with anorexia nervosa have a lower mean...
- 17M.3.SL.TZ2.21c: The photomicrograph shows cardiac muscle. Label the structures I and II.
- 18N.3.HL.TZ0.19b.i: Outline the relationship between systolic blood pressure and hypertension.
- 18N.3.HL.TZ0.19a: Compare and contrast the relationship between BMI and systolic blood pressure in males and...
- 19M.3.SL.TZ2.18b: State the name of the valves that prevent blood flowing from the arteries back into the heart.
- 17N.3.HL.TZ0.22a: Identify the structure labelled X.
- 19M.3.SL.TZ1.15c.i: Compare and contrast the two ECG traces.
- 16N.3.HL.TZ0.22b: Describe the electrical activity that occurs in the heart during the P wave.
- 16N.3.SL.TZ0.15b: Suggest a reason for the difference in QT interval between females with anorexia nervosa and...
- 17M.3.HL.TZ1.19b: Describe how the structure of cardiac muscle cells allows them to transmit impulses.
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18M.3.HL.TZ1.21b.i:
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.
- 18M.3.HL.TZ1.21c: Hypertension has been suggested as a possible cause of CHD. Explain the possible causes of...
- 16N.3.SL.TZ0.15c: State the two causes of normal heart sounds.
- 17M.3.HL.TZ2.19b.ii: Outline the events that occur within the heart that correspond to the QRS complex.
-
16N.3.HL.TZ0.22a:
Using the R–R interval in this ECG, calculate the heart beats per minute (bpm) of this patient. Show your working.
-
18M.3.HL.TZ1.21a:
Outline the role of the sinoatrial node in the contraction of the heart.
- 20N.3.HL.TZ0.22b: State the instrument used by doctors to measure blood pressure.
- 19N.3.SL.TZ0.19: Explain the heart sounds.
-
18M.3.SL.TZ1.16c:
Outline two factors that are related to increased risk of developing CHD.
-
17N.3.HL.TZ0.22b:
Describe the unique properties of cardiac muscle cells.
- 17M.3.HL.TZ2.19b.iii: Severe hypokalemia can lead to ventricular fibrillation. Describe the medical response to...
- 17M.3.SL.TZ1.20b: State what is represented by the period between the points R and R’.
- 17M.3.SL.TZ1.20a: Using the letters provided, identify the parts of the ECG where the ventricle muscles are...
-
17M.3.HL.TZ1.19a:
Samples from cardiac muscle were taken during autopsies from individuals who had coronary heart disease (CHD) and a control group. The histogram shows the relationship between the quantity of cardiac muscle cells and their diameter in the left ventricle in the two groups.
Distinguish between the distribution of cardiac muscle cell diameters in the CHD and control groups.
- 19N.3.HL.TZ0.21c: Explain the heart sounds.
- 19M.3.SL.TZ2.18a: Describe the structure of cardiac muscle cells.
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18N.3.HL.TZ0.19b.ii:
State two effects hypertension can have on the circulatory system.
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19M.3.SL.TZ2.18d:
Sketch the pattern seen in a typical electrocardiogram (ECG) trace for one complete cardiac cycle, including labels of the main features.
-
19M.3.HL.TZ2.22b:
Describe how the structure of cardiac muscle cells allows them to carry out their function.
- 18N.3.HL.TZ0.19c: State how blood pressure and heart rate can be measured.
- 19M.3.HL.TZ1.21b.i: The structure labelled X in the micrograph is a junction between two cardiac muscle cells....
- 19M.3.HL.TZ1.21b.ii: Explain how the structure of cardiac muscle cells allows propagation of stimuli through the...
- 19M.3.HL.TZ2.22a: State one function of the atrioventricular node.
- 18M.3.SL.TZ2.16b: Severe dehydration can lead to cardiac arrest. Outline the use of defibrillation to treat...
- 18N.3.SL.TZ0.17c: Explain what is occurring in the heart during the peak of electrical activity as indicated by...
- 20N.3.HL.TZ0.22c: Describe the mechanism by which the heartbeat is initiated.
- 18M.3.SL.TZ2.15c: The tracker indicated that the student had exceeded the recommended intake of dietary sodium....
- 19M.3.HL.TZ1.21a.ii: Describe briefly how an artificial pacemaker works.
- 17N.3.HL.TZ0.22c: State an early invention that led to improved knowledge of the heart.
- 17N.3.SL.TZ0.16a: State the relationship between pressure and volume in the left ventricle.
- 17M.3.SL.TZ2.21b: Explain the meaning of systolic and diastolic pressure.
- 17M.3.HL.TZ1.19c: Explain the reason for the delay between contractions of the atria and of the ventricles.
- 19M.3.SL.TZ1.15c.ii: Outline one event that occurs in the heart during the T wave.
-
19M.3.SL.TZ2.18c:
Distinguish between the different phases of the cardiac cycle in the atria and in the ventricular muscle.
- 17M.3.HL.TZ1.21b.ii: Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.
-
19M.3.HL.TZ1.21a.i:
State one condition which would require the use of an artificial pacemaker.
- 19N.2.HL.TZ0.1h: Using all the data, discuss whether inoculating mice with the antigen to B. burgdorferi could...
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19N.3.HL.TZ0.21a:
The figure below shows the average death rates from coronary heart disease in the UK.
[Source: Bhatnagar P, Wickramasinghe K, Wilkins E, et al, Trends in the epidemiology
of cardiovascular disease in the UK, Heart 2016; 102: 1945–1952.]Suggest one reason for the general decrease in the incidence of coronary heart disease.
