| Date | November 2017 | Marks available | 6 | Reference code | 17N.3.HL.TZ0.23 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | 23 | Adapted from | N/A |
Question
Discuss high altitude training for athletes.
Markscheme
benefits:
a. improved performance/endurance at lower oxygen levels
OR
improved performance/endurance when returning at low altitude
b. due to higher concentration erythrocytes/red blood cells/hemoglobin
c. more oxygen transported/circulating «due to increase in hemoglobin/RBC number»
d. improved metabolic/lung efficiency/gas exchange
e. increase in myoglobin/number of capillaries/mitochondria
risks:
f. altitude sickness/stroke/lower immunity
g. increased muscle tissue breakdown
h. effects are not immediate/not permanent/extended training at high altitude required
i. may be unfair to competitors who cannot train at high altitude
[Max 6 Marks]
| 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 | Explain | 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
| 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.
State a treatment for emphysema.
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.
Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.
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
supplemental oxygen / breathing techniques / bronchodilators / inhaled steroids / lung surgery to remove damaged tissue / lung transplant
curve has to be towards the right and starting together
Must start together but can finish slightly below the original curve.
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
| Date | May 2016 | Marks available | 3 | Reference code | 16M.3.HL.TZ0.21 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | 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.
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.
During cardiac arrest, the ventricles of the heart might begin to contract in an uncoordinated fashion. Outline the treatment used for this condition.
Explain the role of chemoreceptors in the regulation of ventilation rate.
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 | May 2015 | Marks available | 1 | Reference code | 15M.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
State one mechanism the ileum uses to absorb digested food into the bloodstream.
State the role of the hepatic portal vein.
Label the line that represents the ventricle.
Estimate the total time the atrioventricular valves are open.
Although some CO2 entering the blood simply dissolves in the plasma, most enters the erythrocytes (red blood cells).
Outline how CO2 interacts with hemoglobin once it enters erythrocytes.
Describe the formation of HCO3– in erythrocytes.
Markscheme
active transport/facilitated diffusion/endocytosis
transports blood from (capillaries of) small intestine to (capillaries/sinusoids of) liver
label should connect to solid line on graph.
Candidates should not use region with overlap of dotted and solid lines.
0.4 (s) (allow 0.38 to 0.43)
CO2 attaches to protein portion (not Fe) in heme/carbaminohemoglobin formed;
a. CO2 diffuses into erythrocytes;
b. joins water to form carbonic acid/H2CO3;
c. catalyzed by carbonic anhydrase (inside erythrocytes);
d. H2CO3 dissociates into H+ and HCO3–;
| Date | November 2015 | Marks available | 1 | Reference code | 15N.3.HL.TZ0.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Draw | Question number | 14 | Adapted from | N/A |
Question
The graph shows the oxygen dissociation curve for adult haemoglobin.
State the pathway by which hormones travel from the hypothalamus to the anterior pituitary gland.
State the condition of the blood that would stimulate the release of ADH (vasopressin).
Using the graph, draw a line to show how the oxygen dissociation curve changes with the Bohr shift.
Explain the role of the Bohr shift during vigorous exercise.
Markscheme
(pituitary) portal vein
Do not accept if portal vein is qualified as “hepatic”.
low water content / high blood solute concentration
a. more CO2 is produced which lowers the pH of the blood;
b. hemoglobin releases more oxygen (at lower pH) for same partial pressure of oxygen;
c. more oxygen is available to respiring tissues;
| Date | May 2013 | Marks available | 2 | Reference code | 13M.3.HL.TZ1.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 12 | Adapted from | N/A |
Question
The effects of normal and hypoxic (lower than normal) oxygen concentrations on the oxygen levels in blood and muscles of athletes were investigated in a study. Healthy male non-athletes and athletes performed 30 seconds of intense maximal exertion exercise on a stationary bicycle. The data displayed below show the arterial oxygen saturation levels before, during and after the exercise.
Estimate the change in the arterial oxygen saturation between 30 and 60 seconds in non-athletes under hypoxic conditions.
. . . . . . . . . . . . . . . . . . . . . .%
Compare the effect of hypoxic concentrations on athletes and non-athletes during exercise.
Suggest a reason for the differences.
Explain how the body prevents oxygen saturation levels from falling by more than a small amount during maximal exertion exercise.
Hypoxic concentrations also occur at high altitudes. Explain one effect of high altitude on oxygen transport by blood.
Markscheme
accept range 3.8–4.2 (%)
a. percentage saturation of O2 drops in both during exercise;
b. decrease is greater/more rapid in athletes than in non-athletes;
a. athletes exercise more vigorously/at higher intensity;
b. athletes use more oxygen during exercise;
a. ventilation rate/tidal volume increased;
b. more oxygen absorbed (per minute);
c. heart rate increased;
a. altitude causes formation of more red blood cells/more haemoglobin so/thus the capacity to carry oxygen increases; Idea of capacity is essential although can be OWTTE.
b. the % saturation of blood is lower because there is less oxygen in the atmosphere;
| Date | May 2011 | Marks available | 1 | Reference code | 11M.3.HL.TZ1.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | State | 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.
State the possible cause of the curve shifting from A to B.
On the graph, draw the curve for myoglobin.
Describe the breakdown of hemoglobin in the liver.
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;
graph drawn to left of A;
curve not sigmoid;
As shown below.
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 | 6 | Reference code | 12M.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 oxygen dissociation of myoglobin, completing the graph below to support your answer. Po2 is the partial pressure of oxygen.
Markscheme
myoglobin is specialized for oxygen storage;
myoglobin has a single heme/globin unit/polypeptide chain;
found in muscle;
myoglobin has a higher affinity for oxygen than haemoglobin; (allow this point if haemoglobin dissociation curve correctly drawn to right of myoglobin curve and labelled)
in normal conditions/at rest myoglobin is saturated with oxygen;
used during intense muscle contraction when the oxygen supply is insufficient/whenmuscle is very active its oxygen concentration may fall (below 0.5 kPa);
when this happens myoglobin releases oxygen;
steep rise below 5 kPa with no lag/not sigmoid;
slower rise approaching 100 % above 5 kPa;
| Date | May 2012 | Marks available | 3 | Reference code | 12M.3.HL.TZ2.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Outline | Question number | 14 | Adapted from | N/A |
Question
State one example of a steroid hormone.
State one example of a hormone that is a tyrosine derivative.
Outline the hormonal control of digestive juice secretion in the stomach.
Outline how exercise causes an increase in the ventilation rate.
Markscheme
estrogen / testosterone / progesterone
Accept other verifiable examples.
thyroxine/thyroid hormones / epinephrine / adrenaline / noradrenaline
Accept other verifiable examples
gastrin is secreted when food is in the stomach/chemoreceptors/stretch receptors are stimulated;
stimulates gastric acid/pepsinogen production;
when pH drops too low, gastrin secretion is inhibited by (secretin and somatostatin) hormones;
exercise uses energy/ATP/increases metabolic rate/aerobic respiration;
which causes increased CO2 which lowers blood pH;
detected by chemosensors in aorta/carotid arteries;
stimulate medulla/breathing centre of brain;
nerve impulses to diaphragm and intercostal muscles increase contraction (rate);
| Date | May 2010 | Marks available | 2 | Reference code | 10M.3.HL.TZ1.13 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Predict | Question number | 13 | Adapted from | N/A |
Question
The human body suffers significant physiological changes at extreme altitudes. Extensive scientific information has been obtained from medical research expeditions to Mount Everest (8848 m above sea level). The figure below shows the relationship between the partial pressures of oxygen (Po2) and carbon dioxide (Pco2) in the alveoli as altitude increases from sea level (at top right) to the summit of Mt. Everest (at bottom left).
The table below shows the data from the field study on the alveolar gas and arterial blood values for a climber at sea level and on the summit of Mt. Everest.
Outline the changes in the partial pressures of carbon dioxide and oxygen as altitude increases.
Predict, with a reason, how the ventilation rate will change as a climber ascends from sea level to the summit of Mt. Everest.
Calculate the percentage change in the arterial partial pressure of carbon dioxide (Pco2) at the summit compared with that at sea level.
Suggest a reason for the low arterial partial pressure of carbon dioxide at the summit.
State one adaptation of people who live permanently in high altitude areas.
Markscheme
both Po2 and Pco2 fall with increasing altitude;
above certain altitude there is little change in alveolar Po2 / Po2 remains close to 37 mm Hg over a wide range of altitudes;
Pco2 changes over the entire range of altitudes;
the Po2 is always higher than Pco2;
the rate of ventilation would increase;
expelling large quantity of CO2 / causing fall in blood CO2/Pco2;
rise in blood pH hampers ventilation/inhibits chemoreceptors;
(Allow answers in the range 81–81.5 %)
low partial pressure/level of carbon dioxide in the air;
hyperventilation/high rate of ventilation;
high lung capacity;
larger tidal volumes;
high proportion of hemoglobin / high red blood cell count;
hemoglobin with higher affinity for oxygen;
| Date | November 2012 | Marks available | 1 | Reference code | 12N.3.HL.TZ0.13 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Calculate | Question number | 13 | Adapted from | N/A |
Question
Researchers explored the effects of roadside traffic exposure in London on people with asthma. Each participant walked for two hours through Hyde Park, a large traffic-free park, and on a separate occasion along Oxford Street, where diesel-powered buses and taxicabs are permitted. The researchers measured the pH of the participants’ exhaled breath two hours before each walk and three hours and six hours after the start of each walk. The level of an inflammation indicator, myeloperoxidase, was also measured the day after the experiment.
Calculate the percentage increase of myeloperoxidase between Hyde Park and Oxford Street for participants.
Compare the changes in exhaled breath pH caused by walking through Hyde Park and along Oxford Street.
Explain the changes in exhaled breath pH caused by walking along Oxford Street in people with asthma.
Markscheme
625 % (percentage required) (accept answers in the range of 600 % to 650 %)
pH rises in Hyde Park and falls along Oxford Street;
back to pre-walk level in six hours in Hype Park but not along Oxford Street;
asthma (attack) constricts bronchioles (while walking);
exercise/walking increases cell respiration producing more CO2;
lower ventilation causes CO2 build-up thus lower pH;
CO2/pollutants in the air could be causing/triggering acidification;
inflammation (by-products) lower pH;
| Date | November 2009 | Marks available | 6 | Reference code | 09N.3.HL.TZ0.15 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 15 | Adapted from | N/A |
Question
Explain how and why ventilation rate varies with exercise.
Markscheme
during exercise the rate of tissue respiration increases/more carbon dioxide produced;
carbon dioxide production in the tissues exceeds the rate of breathing it out;
increase in carbonic acid / increase in H ions / pH drops in the blood plasma;
lactic acid (in strenuous exercise) reduces pH;
chemoreceptors/chemosensors detect change in pH/increase in carbon dioxide/ decrease in oxygen;
receptors in the carotid/aortic bodies;
nerve impulses sent to the breathing centres of the brain;
nerve impulses then sent to diaphragm/intercostal muscles;
negative feedback control;
| Date | November 2010 | Marks available | 6 | Reference code | 10N.3.HL.TZ0.15 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 15 | Adapted from | N/A |
Question
Explain the oxygen dissociation curves of adult hemoglobin, fetal hemoglobin and myoglobin.
Markscheme
adult hemoglobin: [2 max]
a. rapid saturation of oxygen in the lungs;
b. rapid dissociation of oxygen as the oxygen concentration decreases;
c. oxygen released in the tissues where needed;
fetal hemoglobin: [2 max]
d. fetal hemoglobin curve to the left of adult hemoglobin;
e. higher affinity for oxygen than adult hemoglobin;
f. oxygen moves from adult hemoglobin to fetal hemoglobin;
myoglobin: [2 max]
g. myoglobin to the left of fetal hemoglobin;
h. higher affinity for oxygen than adult hemoglobin;
i. only releases oxygen at very low oxygen concentrations/in tissues;
j. oxygen reserve;