IB DP Physics Option D: Human physiology (Core topics) :D.4 The heart HL Paper 3

Date	November 2017	Marks available	1	Reference code	17N.3.HL.TZ0.22
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	State	Question number	22	Adapted from	N/A

Question

The micrograph shows a section of cardiac muscle.

[Source: Musculocardiaco by Goyitrina (https://commons.wikimedia.org/wiki/File:Musculocardiaco.jpg)]

Identify the structure labelled X.

[1]

Describe the unique properties of cardiac muscle cells.

[4]

State an early invention that led to improved knowledge of the heart.

[1]

Markscheme

intercalated disc

a. cells are myogenic/self-excitatory

b. cells are joined end to end

cells are joined by intercalated disc

c. «intercalated discs» allow for faster propagation «of signal»

d. cells contract together for coordinated contraction

e. contain many mitochondria

f. cells are branching/Y-shaped

g. controlled by pacemaker/sinoatrial/SA and atrioventricular/AV nodes

[Max 4 Marks]

stethoscope

electrocardiograph/ECG

Allow other valid example.

Date	May 2017	Marks available	3	Reference code	17M.3.HL.TZ2.19
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	Outline	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.

[2]

b.i.

Outline the events that occur within the heart that correspond to the QRS complex.

[3]

b.ii.

Severe hypokalemia can lead to ventricular fibrillation. Describe the medical response to ventricular fibrillation.

[3]

b.iii.

Sometimes hyperkalemia occurs as a body tries to respond to low blood pH. State the normal range of blood pH in the human body.

[1]

b.iv.

Explain how low blood pH causes hyperventilation (rapid breathing).

[3]

b.v.

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

b.i.

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

b.ii.

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

b.iii.

around 7.4 or 7.35 to 7.45

b.iv.

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

b.v.

Date	May 2017	Marks available	2	Reference code	17M.3.HL.TZ1.21
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Explain	Question number	21	Adapted from	N/A

Question

The graph below shows the oxygen dissociation curve at a low CO2 concentration.

Outline the main changes in the lungs that occur in patients with emphysema.

[2]

a.i.

State a treatment for emphysema.

[1]

a.ii.

An increase in metabolic activity results in greater release of CO2 into the blood. On the graph, draw the oxygen dissociation curve during intense exercise when the CO2 concentration of the blood is high.

[1]

b.i.

Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.

[2]

b.ii.

Markscheme

a. air sacs/alveoli break down/rupture

b. creating one larger air space instead of many small ones / reduces the surface area of the lungs

c. loss of elasticity of lung tissue

a.i.

supplemental oxygen / breathing techniques / bronchodilators / inhaled steroids / lung surgery to remove damaged tissue / lung transplant

a.ii.

curve has to be towards the right and starting together

Must start together but can finish slightly below the original curve.

b.i.

a. increased levels of CO2 lower the pH of the blood

b. «which results in» decreased affinity of the hemoglobin for oxygen / greater release of oxygen

c. this shifts the oxygen dissociation curve to the right/Bohr shift

b.ii.

Date	May 2017	Marks available	2	Reference code	17M.3.HL.TZ1.19
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Explain	Question number	19	Adapted from	N/A

Question

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.

[1]

Describe how the structure of cardiac muscle cells allows them to transmit impulses.

[3]

Explain the reason for the delay between contractions of the atria and of the ventricles.

[2]

Markscheme

a. CHD has wider range/spread/more variation of diameter values / vice versa

b. control has higher percentage/proportion/peak in middle values (accept numbers between 8–12)

Accept numerical statement supporting this

a. are branched/ have a Y-shape/ interconnected / connect to several neighbouring «cardiac» cells

b. intercalated discs are special regions of/junctions between plasma membranes

c. provide electrical coupling / enable rapid transmission of «electrical» impulses «between cells»

d. ion channels in membranes

e. «ease of» flow of ions allows action potentials to spread «between cardiac cells»
OR
«ease of» flow of ions allows rhythmic depolarization

f. trigger action potentials without nervous input

Accept annotated drawings.

a. impulses from atria do not pass directly to ventricles «due to layer of fibrous material»

b. travel to ventricle via atrio-ventricular node/AVN in wall of right atrium

c. impulses from AVN sent along Bundle of His /conducting fibres/Purkinje fibres

d. ensures that the atria have ejected their blood into the ventricles first before the ventricles contract

Date	November 2016	Marks available	2	Reference code	16N.3.HL.TZ0.22
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Explain	Question number	22	Adapted from	N/A

Question

The electrocardiogram (ECG) of a normal patient after exercise is shown.

Using the R–R interval in this ECG, calculate the heart beats per minute (bpm) of this patient. Show your working.

[2]

Describe the electrical activity that occurs in the heart during the P wave.

[1]

Explain why the QRS wave has a larger amplitude than a P wave.

[2]

Markscheme

a. determining time of 1 beat = 0.46 «seconds»

b. correct calculation of heart rate/beats per minute = 130 «bpm»

Other possible calculations

eg:

23 «squares» × 0.02 «sec» = 0.46

2.3 × 0.2 «sec» = 0.46

atrial depolarization/electrical impulse travels from the sinoatrial/SA node to the atrioventricular/AV node

Accept atrial systole.

a. atrium has a small contraction requiring low electrical charge/OWTTE

b. the QRS complex shows the depolarization of the «right and left» ventricles

Accept ventricular systole.

c. the ventricles have a large muscle mass compared to the atria, so the QRS complex has a larger amplitude than the P wave/OWTTE
OR
ventricle contraction needs more electricity than atrial contraction/OWTTE

Accept answers implying large muscle mass eg, stronger contraction, more pressure, etc.

Date	May 2016	Marks available	1	Reference code	16M.3.HL.TZ0.21
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Outline	Question number	21	Adapted from	N/A

Question

The diagram shows an ECG trace with the QRS complex indicated.

Outline the events of the cardiac cycle that are occurring during this QRS interval.

[2]

Heart rate is affected by the hormone epinephrine. The action of epinephrine is mediated by a chemical called a second messenger. Explain the mechanism of action of a second messenger.

[3]

During cardiac arrest, the ventricles of the heart might begin to contract in an uncoordinated fashion. Outline the treatment used for this condition.

[1]

Explain the role of chemoreceptors in the regulation of ventilation rate.

[3]

Markscheme

Septum depolarizes
OR
Signal from AVN/atrioventricular node

Conducting fibers carry impulses through the ventricle wall
OR
Carry impulse through Bundle of His/Purkinje fibers

Ventricles depolarize
OR
Atrioventricular valves close Do not accept the alternative mp if other valves closing is mentioned as well.

Atria repolarize

Ventricle contraction/systole initiated

Epinephrine/peptide/protein/hydrophilic hormones bind to «receptors in» plasma membrane

Involves synthesis/release/activation of second messenger/cyclic AMP/cAMP

Triggers cascade of events

Leads to promotion/inhibition of enzymes
OR
Causes activation of protein kinase

Causes the hormone effect

Use a defibrillator to restore/reset normal rhythm/to shock the heart/restore heart beat (Do not accept pacemaker)
OR
Application of an electric discharge to the chest to restore normal rhythm

Need something more than one word answer as this is an “outline”.

High CO2 levels lead to decrease in pH/increased acidity (Accept inverse statements using low CO2 concentration/higher pH)

Chemoreceptors found in the medulla oblongata/aorta/carotid artery

They are able to detect a change in blood pH/CO2 concentration

«Chemoreceptors» send message/impulse to the respiratory centre

Respiratory centre «in medulla oblongata» controls ventilation rate

Triggers an increase in the ventilation rate to rid the body of CO2

Date	November 2015	Marks available	1	Reference code	15N.3.HL.TZ0.13
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Calculate	Question number	13	Adapted from	N/A

Question

Coronary heart disease (CHD) is common in some families, with men being more susceptible to the disease than women. Researchers in Finland carried out an investigation to determine whether the pattern within families was the same for women as for men. The graph shows how the risk of developing CHD in men and women of certain ages depends on whether they had a brother or sister with the disease.

State the risk of a man developing CHD between the ages of 55–59 if his brother had CHD.

[1]

Calculate the increase in risk over the control group for a woman of 60–64 of developing CHD if her sister had the disease.

[1]

Compare the results for the men and the women.

[3]

Suggest two reasons why a man is more likely to develop CHD if his brother had the disease.

[2]

Markscheme

35 %

15 %

a. both show an increase in the risk of CHD as age increases;

b. men/women with (either) siblings with CHD show an increased risk (relative to their control);

c. men have greater risk than women of developing CHD (at all ages);

d. both men and women/women only are more likely to develop CHD if their sister has the disease;

e. men with a brother with CHD have a greater risk than women with a brother with CHD;

Accept any other valid comparison using the graph.

a. hereditary/genetic predisposition;

b. similar (unhealthy) lifestyles/diets;

Date	May 2013	Marks available	6	Reference code	13M.3.HL.TZ2.15
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	Explain	Question number	15	Adapted from	N/A

Question

Explain the events of the cardiac cycle, including the heart sounds.

Markscheme

a. during diastole the heart muscles/atria/ventricles are relaxed;
b. blood enters the atria;
c. during atrial systole the atria contract and blood moves into the ventricles;
d. pressure (in ventricles) causes bicuspid/tricuspid/AV valves to close;
e. (this) closing of valves causes first heart sound;
f. during ventricular systole the ventricles contract causing blood to flow to aorta/pulmonary artery/arteries/out of heart;
g. semilunar valves close so blood does not return to the ventricles;
h. this causes the second heart sound;
i. blood leaving atria/ventricles during contraction is caused by increased pressure which reduces volume;

Date	May 2011	Marks available	2	Reference code	11M.3.HL.TZ1.14
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Outline	Question number	14	Adapted from	N/A

Question

The oxygen dissociation curve is a graph that shows the percentage saturation of hemoglobin at various partial pressures of oxygen. Curve A shows the dissociation at a pH of 7 and curve B shows the dissociation at a different pH.

Outline how coronary thrombosis can be caused.

[2]

State the possible cause of the curve shifting from A to B.

[1]

b (i).

On the graph, draw the curve for myoglobin.

[2]

b (ii).

Describe the breakdown of hemoglobin in the liver.

[2]

Markscheme

atheroma/fatty deposits in arteries;
hardening of arteries/atherosclerosis/arteriosclerosis;
rough surface causes rupture of platelets;
clots form in coronary artery;

increase in CO2 concentration;
decrease in pH;

b (i).

graph drawn to left of A;
curve not sigmoid;
As shown below.

b (ii).

hemoglobin absorbed by phagocytes/Kupffer cells;
split into heme and globins;
globin hydrolysed/broken down to amino acids;
iron removed from heme group / heme broken down to form bilirubin/bile pigment;

Date	May 2012	Marks available	2	Reference code	12M.3.HL.TZ1.14
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Outline	Question number	14	Adapted from	N/A

Question

In healthy adults, there are heart sounds during the cardiac cycle. Outline the causes of two of these sounds.

[2]

State two products resulting from the breakdown of erythrocytes (red blood cells) in the liver.

1. …………………………………………………………

2. …………………………………………………………

[2]

Compare gastric juice and pancreatic juice.

[3]

List one material that is egested after human digestion.

[1]

Markscheme

changing pressure of blood in heart automatically opens and closes the valves / the closing of valves generates the heart sounds;
first heart sound (S1) is produced by the closing of the AV valves/mitral and tricuspid valves;
second heart sound (S2) produced by the closing of semilunar valves/aortic and pulmonary valves;

iron;
bile pigments/bilirubin;
globin/amino acids;

Award [1] for each correct row.

cellulose / lignin / bile pigments / intestinal cells / bacteria

Date	May 2012	Marks available	3	Reference code	12M.3.HL.TZ2.13
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	Deduce	Question number	13	Adapted from	N/A

Question

In patients with coronary heart failure (CHF), the presence of anemia can increase the risk of mortality. Anemia is a shortage of red blood cells or a reduced concentration of hemoglobin in the blood. Hepcidin is a peptide that is synthesized in the liver to suppress iron absorption in the intestine. The blood hepcidin concentration in CHF patients with anemia and without anemia was measured. The control group did not have cardiac disease or anemia.

State which group has the greatest range of blood hepcidin concentration.

[1]

Calculate the difference in median blood hepcidin concentration for CHF patients with anemia and without anemia, giving the units.

[1]

Using the data, deduce whether the incidence of CHF or the incidence of anemia has a greater effect on the blood hepcidin concentration.

[3]

Iron is necessary for hemoglobin to carry oxygen so low iron levels cause low levels of hemoglobin. Suggest reasons for the levels of hepcidin found in CHF patients with anemia.

[2]

Markscheme

CHF without anemia

9 ng cm–3 (calculation not required, accept answers in the range of 8.5 ng cm–3 to 9.2 ng cm–3)

median of CHF without anemia greater than median of CHF with anemia;
median of CHF without anemia similar to median of control;
median of CHF with anemia lower than median of control;
anemia (with CHF) appears to be more significant than CHF (without anemia) in affecting hepcidin concentrations;
difficult to determine as overlaps of ranges/population sizes not given/no control with anemia;

low hepcidin levels in CHF patients with anemia;
low hepcidin allows more iron intake/absorption;
more iron allows more hemoglobin so less anemia / low iron leads to anemia;
low iron levels exert negative feedback on hepcidin production;

Date	May 2010	Marks available	6	Reference code	10M.3.HL.TZ1.15
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Explain	Question number	15	Adapted from	N/A

Question

Explain the role of the SA (sinoatrial) node in the cardiac cycle.

Markscheme

SA node is located in the wall of right atrium of heart muscle;
has characteristics of both nerve and muscle tissue;
SA node initiates each impulse;
acts as pacemaker of the heart;
no nerve impulses needed for contraction / myogenic;
connected to nerves which slow/accelerate heart rate;
impulses spread out in all directions through walls of atria;
stimulates atrial systole/contraction;
fibres in walls of atria prevent impulses from reaching ventricles;
impulses reach AV node (after atrial contraction);

Date	November 2010	Marks available	1	Reference code	10N.3.HL.TZ0.13
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	State	Question number	13	Adapted from	N/A

Question

Alcohol is known to increase the risk of cardiovascular disease (CVD). An investigation was undertaken to look at the effects of drinking different amounts of alcohol in men and women.

C-reactive protein (CRP), fibrinogen and total white blood cell count (WBC) were measured. These are markers that can be used to measure the risk of cardiovascular disease (CVD).

Samples were taken from populations in three different countries and their drinking habits were determined and their blood was analysed.

State the overall trend for CRP for men and women over the range of alcohol consumption.

[1]

Evaluate, using all the data, whether drinking small amounts of alcohol reduces the risk of CVD.

[3]

Deduce which is the best marker to measure the risk of CVD.

[1]

Outline atherosclerosis and the causes of CVD.

[2]

Markscheme

a. for both men and women a decrease is seen at the lowest alcohol intake followed by an increase;

b. the level of CRP is higher in women than in men over the range of alcohol consumption / as the intake increases the difference between men and women increases, the CRP increase being greater in women;

a. drinking small amounts of alcohol seems to reduce the level of all markers / drinking none and/or high amounts of alcohol has higher levels of markers than moderate amount;

b. the effect of small amounts of alcohol is less in women than in men / the effect of large amounts of alcohol is greater in women than in men / women should consume less than men;

c. other effects of alcohol consumption are not measured;

d. other factors increasing risk of CVD are not measured;

e. the type of alcohol is not stated / the active factor in the drink is not seen;

CRP shows the decrease in risk for low amounts of alcohol then increases above the baseline for higher amounts

a. high blood pressure damages endothelial wall;

b. WBC/macrophages build up cholesterol;

c. plaque hardens arterial wall / blocks lumen / artery blocked by depositions in wall;

d. wall rough;

e. clots form;