IG CIE B11 Gas Exchange in Humans

What is ventilation?

The movement of air between the environment and the lungs via inhalation and exhalation

What are the features of gas exchange surfaces in humans?

large surface area, thin surface, good blood supply and good ventilation with air

Why is it advantageous to have large numbers of alveoli?

Provides a large surface area for gas exchange to occur across

What is wrong with this answer: "alveoli and capillary cell walls are thin"? Correct it

alveoli and capillaries are made of animal cells (animal cells do not have cell walls!) Instead sya "alveoli and capillaries have thin walls" or "the walls are one cell thick"

What is the function of cartilage in the trachea?

Cartilage is flexible yet has more rigidity than other tissues. It serves to keep tubes open.

Describe and explain how the lungs are adapted for gas exchange

Large number of alveoli so very large surface area.

Alveoli have thin walls so short distance for diffusion

Moist surface so oxygen dissolve before diffusion

Many capillaries provide a good blood supply so oxygen supplied quickly & carbon dioxide removed quickly which maintains a steep concentration gradient

Good ventilation with air which maintains steep concentration gradient

Describe inhalation / inspiration

The diaphragm contracts & flattens.

The external intercostal muscles contract (and the internal intercostal muscles relax).

The causes the ribs to move up and out.

The volume in the thorax increases.

This decreases the pressure in the thorax

Since atmospheric pressure (outside the lungs) is greater, air moves into the lungs.

Describe exhalation / expiration

The diaphragm relaxes & curves upwards (becomes dome-shaped - due to pressure from the organs beneath - liver, stomach)

The internal intercostal muscles contract (and the external intercostal muscles relax)

The causes the ribs to move down and in

The volume in the thorax decreases.

This increases the pressure in the thorax

Since atmospheric pressure (outside the lungs) is lower than in the thorax, air moves out of the lungs.

Describe the role of goblet cells and cilia in the airways

Goblet cells secrete mucus. Pathogens and dust that enter the trachea get trapped in the mucus. The cilia wave to move the mucus, dust and pathogens away from the lungs. At the back of the through the mucus is swallowed.

How are the lungs protected from pathogens?

Goblet cells secrete mucus. Pathogens and dust that enter the trachea get trapped in the mucus. The cilia wave to move the mucus, dust and pathogens away from the lungs. At the back of the through the mucus is swallowed.

What is the difference in carbon dioxide concentration in inhaled and exhaled air?

More carbon dioxide in exhaled air than inhaled (or vica versa)

Explain why there is a difference in carbon dioxide concentration in inhaled and exhaled air

Cells carrying out aerobic respiration produce carbon dioxide, which needs to be exhaled

What is the difference in oxygen concentration in inhaled and exhaled air?

More oxygen in inhaled air than exhaled (or vica versa)

Explain why there is a difference in oxygen concentration in inhaled and exhaled air

Cells carrying out aerobic respiration use oxygen, so there is less exhaled than inhaled

Compare the composition of inhaled and exhaled air

Inhaled air: more oxygen, less carbon dioxide, less water vapour

Inhaled & exhaled air: same nitrogen, same noble gases"

List the differences in composition of inhaled and exhaled air

Inhaled air: more oxygen, less carbon dioxide, less water vapour

What is the test for carbon dioxide?

Bubble gas / exhale through limewater. If it turns from clear to cloudy carbon dioxide is present

What could you measure about breathing?

Count the number of breaths, or breathe into a spirometer to measure number of breaths or volume of air exhaled

What effect does exercise have on breathing?

When exercising we breathe faster and deeper

When we exercise, what detects the increase of carbon dioxide in the blood and sends a nervous impulse to the intercostal muscles?

The brain!

Explain why breathing rate and depth increase when we exercise

An increase in physical activity leads to an increase in respiration.

An increase in respiration leads to an increase in carbon dioxide in the blood.

This increase in carbon dioxide is detected by the medulla in the brain.

The brain sends nerve impulses to the external intercostal muscles and diaphragm to contract to cause more regular and deeper breaths.

If the task is "Plan an investigation to test the effect of exercise on breathing rate" What could your independent variable be?

Doing exercise and not doing exercise. E.g. sit still versus 30 star jumps or sit still versus running 20 stairs

OR doing exercise for different lengths of time E.g. 0 minutes, 2 minutes, 4 minutes, 6 minutes, 8 minutes and 10 minutes of star jumps

If the task is "Plan an investigation to test the effect of exercise on breathing rate" What could your dependent variable be?

Count the number of breaths in a set period of time e.g. 1 minute

Plan an investigation to test the effect of exercise on breathing rate

Things to include; talk about safety, talk about who will take part in the experiment, step-by-step method, say you will repeat it and calculate averages (5 marks)

Example:

Ensure the participant is made aware of what the experiment involves, exercise is carried out in a safe location and the student has no health issues.

The larger the sample of participants the more reliable the results will be.

Participants should be the same age, gender, not smoke and not drink alcohol so their results are as comparable as possible.

1.Count the number of breaths in one minute at rest OR

2.Exhale a normal breath into a spirometer

3.Do star jumps for 2 minutes.

4.Repeat stages 1 and 2.

5.Rest until breathing depth and rate has returned to normal.

6.Do star jumps for 4 minutes.

7.Repeat stages 1 and 2.

8.Collect data for 5 different lengths of exercise and have 5 repeats for each.

9.Calculate averages

10. Compare number of breaths at rest and the 5 different lengths of exercise

Draw a results table that could be used to collect the results

IV = Number of star jumps on the left hand side

DV = number of breaths on the right hand side

Columns for 5 trials and an average column

No units needed as they are counts