Ventilation and the thorax

A scientist measures the oxygen uptake and carbon dioxide output of an athlete on an exercise bike at increasing work rates.

The results are shown in the graph.

What are the results shown in the graph?

A There is a negative correlation between oxygen uptake and work rate.

B There is a positive correlation between carbon dioxide output and work rate up to 300 W after which the correlation becomes negative.

C There is a positive correlation between oxygen uptake and work rate.

D There is no correlation between carbon dioxide output and work rate.

Your answer

Following a period of intense exercise an athlete breathes out forcefully.

Which option describes the mechanism of forceful expiration in this athlete?

A The diaphragm contracts and the internal intercostal muscles contract.

B The diaphragm relaxes and the internal intercostal muscles relax.

C The external intercostal muscles contract and the internal intercostal muscles relax.

D The external intercostal muscles relax and the internal intercostal muscles contract.

Your answer

Ventilation of the lungs involves muscles working together.

Which option describes expiration?

A In expiration at rest, the external intercostal muscles and the diaphragm relax and the rib cage moves down and in.

B In expiration at rest, the internal intercostal muscles and the diaphragm contract pulling the rib cage down and in.

C In forced expiration, the diaphragm relaxes and the external intercostal muscles contract pulling the rib cage down and in.

D In forced expiration, the internal intercostal muscles and the diaphragm contract pulling the rib cage down and in.

Your answer

The table compares the features of airways in the lungs.

Complete the table by putting a tick (✓) in each box if the feature is present and a cross (8 the feature is absent in each structure.

The first row has been completed for you.

Question 21(b) begins on page 30

Ventilation of the lungs creates air movements that can be measured and recorded.

Name the apparatus used to measure and record these air movements.

The trace below shows a recording of ventilation movements from an individual subject.

Use the trace to estimate the maximum value for tidal volume during the first minute.

After 60 seconds, the subject was told to breathe in as deeply as possible and then breathe out fully.

Use the trace to calculate the vital capacity of the subject.

* Compare and contrast the mechanism of expiration during the first 60 seconds of the trace with the mechanism of expiration when the subject was told to breathe out fully.

Additional answer space if required.

Complete the following statements about exchange surfaces.

Use the correct terms selected from the list below.

circulatory system concentration gradient diffusion pathway

flow of air lung capacity surface area

surface area to volume ratio ventilation

Large organisms have a large........ but they

have a small........ This means they need

a specialised exchange surface and a........

Two features of an efficient exchange surface are:

1. A good blood supply to maintain the........

2. A short........

Peak expiratory flow (PEF) is a measure of the maximum rate at which a person can exhale.

The graph below shows the typical PEF values for men of different ages and heights.

Which of the following is the percentage increase from the PEF of a 20 year old man of 175 cm to the PEF of a 45 year old man of 183 cm?

A 19.4%

B 10.9%

C 12.3%

D 8.1%

Your answer

Gestational diabetes is a medical condition that affects pregnant women. It results in high levels of glucose in the blood, even though the woman produces normal levels of insulin.

Gestational diabetes is most similar to which other type of diabetes?

Explain your answer.

Suggest two ways a woman with gestational diabetes can manage her condition.

Skeletal muscle is one of the main tissues where glucose is removed from the blood in response to insulin.

Name the other tissue.

Explain why glucose is required for the contraction of skeletal muscle.

During late pregnancy, women find ventilation more difficult, as the developing foetus reduces the volume of the thorax. This can lead to tiredness and difficulty breathing.

A student used a spirometer to measure ventilation in a woman who was 36 weeks pregnant.

Fig. 16.1 shows the trace produced.

Mean oxygen uptake rate at rest in women is around 0.020 dm³ s^–1.

Using these data, the student made the following conclusion:

My data show that being pregnant reduces rate of oxygen uptake by up to 20%.

Evaluate this claim, using the data in Fig. 16.1.

The greater blue-ringed octopus, Hapalochlaena lunulata, is one of the most venomous of all animals.

Its bite contains tetrodotoxin (TTX), a neurotoxin that can cause paralysis and death within minutes.

The following information has been discovered about the effects of TTX on nerve cells:

• TTX binds to the external surface of the voltage-gated sodium ion channels in the axon membrane.

• Binding of TTX changes the tertiary structure of the channel.

• This means the channel cannot open.

Using the information provided, explain how TTX affects the activity of neurones.

A common cause of death from TTX poisoning is suffocation (not getting enough oxygen) as a result of paralysis of the diaphragm.

Explain how paralysis of the diaphragm could lead to suffocation.

TTX is also known to reduce the speed of conduction in the Purkyne fibres of the heart.

Suggest and explain what effect this would have on the heart rate.

Molluscs such as H. lunulata have unmyelinated neurones. Saltatory conduction cannot occur in these neurones.

Why is transmission of action potentials along the axon slower in the absence of saltatory conduction?

Many organisms have evolved specialised gas exchange surfaces. One feature of these structures is their large surface area to volume ratio.

Describe how the structures of the insect tracheal system and fish gills provide a large surface area for gas exchange.

insect tracheal system........

The lugworm, Arenicola marina, is a species of segmented worm that lives in burrows in damp sand. They have hair-like external gills that increase the surface area available for gas exchange.

Many other species of segmented worm do not have external gills.

Suggest why lugworms have evolved external gills