Breathing system & plant gaseous exchange



|3.4 Breathing System |Objectives |Green |Orange |Red |

| |Can you | | | |

|3.4.4 Lungs & Breathing |Draw and identify the breathing tract in humans | | | |

| |Give the function of the parts: Nasal and buccal cavities, pharynx, epiglottis, glottis, | | | |

| |larynx, trachea, bronchi, bronchioles, alveoli | | | |

| |Explain the essential features of the alveoli and capillaries as surfaces over which gas | | | |

| |exchange takes place | | | |

| |Describe the mechanism of breathing -- how we inhale and exhale air | | | |

| |Give the role of the diaphragm, the intercostal muscles and brain (exclude CO2 levels) in | | | |

| |breathing | | | |

| |Explain pressure changes in the thoracic cavity during breathing | | | |

| |Outline gaseous exchange in alveoli | | | |

| |Give the role of haemoglobin in oxygen transport | | | |

| |Explain source of carbon dioxide from the plasma | | | |

| |Explain water vapour exhalation. | | | |

| |Carry out the breathing exchange experiment using limewater or bicarbonate indicator | | | |

| |Describe the experiment to show the effect of exercise on the breathing rate | | | |

| |Compare healthy lungs with lungs of unhealthy respiratory systems and note the differences | | | |

| |Demonstrate the effect of cigarette smoking using cotton wool, bicarbonate indicator, etc | | | |

| |Explain one breathing disorder, e.g. from asthma and bronchitis | | | |

| |Give possible causes of the disorder | | | |

| |Describe prevention and treatment of the disorder | | | |

Self-Assessment

Green. I know it all

Orange I have some idea

Red I need to start studying this section

Gaseous exchange (external respiration) refers to the need to take in oxygen and release carbon dioxide.

Respiratory organs

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1. Nose/Mouth: The air enters through the nose and the mouth. The hairs and mucus in the nose filter dust and microbes out of the air. The air is also warmed, which aids in efficient gas diffusion and moistened, which prevents the alveoli from drying out.

2. Trachea: windpipe. It has rings of cartilage, which keeps it open.

Mucus trap particles such as dust, bacteria and viruses and cilia sweep up the mucus into the oesophagus where it is swallowed.

3. Epiglottis: The epiglottis is a flap of cartilage that covers the opening to the trachea (glottis) and stops food from entering it.

4. Larynx: voicebox. The vocal cords vibrate to produce sound.

5. Bronchus: a branch of the trachea leading to each lung.

6. Bronchioles: further divisions of the bronchi that allow air in and out of the alveoli.

7. Alveoli: The alveoli are sacs in which gas exchange occurs. They allow diffusion by being one-celled thick, having a moist lining and being enclosed in an extensive network of capillaries.

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Oxygen dissolves in the film of water lining the alveolus and then diffuses through the alveolus and capillary walls into the red blood corpuscles in the blood. Here it combines with haemoglobin to form oxyhaemoglobin

Carbon dioxide and water vapour diffuse from the blood plasma through the alveolar wall and into the film of water and then into the alveolus. Finally it is removed from the lungs during expiration.

Adaptations of alveoli for gas exchange:

1. Large surface area of contact between alveoli and blood capillaries

2. Alveoli and capillaries are only one-celled thick thus giving a short distance for diffusion.

3. Slow blood flow in capillaries allowing time for diffusion to occur.

4. Alveoli lining is moist - dissolved gases diffuse faster.

Transport of gases

Oxygen is mostly transported by haemoglobin in red blood cells. Carbon dioxide is mostly carried dissolved in plasma.

Breathing mechanism

Inhalation

1. The diaphragm contracts and the diaphragm flattens.

2. The intercostal muscle contract pulling the ribcage up and out

3. The volume of the thoracic cavity increases.

4. The pressure inside the lungs decreases.

5. Air rushes into the lungs to equalise the pressure inside and outside.

Inhalation is active – requires energy for muscles to contract.

Exhalation

1. The diaphragm relaxes and moves up

2. The intercostal muscles relax causing the ribcage to move down and in.

3. The volume of the thoracic cavity decreases.

4. The air pressure inside the lungs decreases.

5. Therefore air is forced out of the lungs until the pressure is equalised between the inside and the outside.

Exhalation is passive – does not use energy.

Learn one breathing disorder

Asthma

Asthma is a difficulty in breathing caused by the narrowing of the smaller bronchioles. This is due to the contraction of the muscles in bronchiole walls and inflammation of the wall lining. Cells lining airways make more mucus(phlegm) than normal.

Symptoms

• Coughing

• wheezing

• tightness of chest

• breathlessness

Cause

• Common asthma triggers include allergens such as dust, pollen, animal hair and cold air.

Prevention

• Remove triggers such as allergens

• Installing air filters

• Steroid inhaler(‘preventer’)

Treatment

• Bronchodilator inhalers (‘reliever’) relax the smooth muscle of bronchiole lining and cause them to dilate.

Bronchitis is an inflammation of the bronchi.

Emphysema is a condition of irreversible lung damage and heart failure.

Chronic obstructive pulmonary disease or COPD is chronic bronchitis and emphysema found together.

Control of breathing

Breathing is an involuntary action. It is under the control of the medulla oblongata in the brain. It measures the levels of CO2 in the blood by measuring its pH. High CO2 levels (pH lower – carbonic acid) increase the depth and rate of breathing. We can override the subconscious for a short time e.g. speaking, swimming or singing, swallowing, laughing when we control the timing of our breathing. Holding your breath will eventually lead to unconsciousness, at which point normal breathing resumes.

Expt: Artificial lung experiment

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Inhalation:

When the rubber (diaphragm) is pulled down the volume increases, thus pressure decreases and the balloons inflate.

Exhalation:

When the rubber is pushed up the volume decrease, pressure increases and the balloon deflates.

Expt – Carry out the breathing exchange experiment using limewater.

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ME: To show the effect of exercise on the rate of breathing

Safety precautions

Don’t do if feeling unwell, sick recently, bad asthma, light-headed

Procedure:

Rest for 5 minutes. Count your resting rate – can watch your partner’s ribcage moving. Repeat twice and get an average.

• Repeat for gentle exercise e.g. walking for 3 minutes, measure and record breathing rate for 5 consecutive minutes or until breathing rate returns to normal.

• Do strenuous exercise e.g. running for 3 minutes. measure and record breathing rate for 5 consecutive minutes or until breathing rate returns to normal.

Result:

• Exercise increases rate and depth of breathing.

• Average breathing rate = 15 per min.

• A fit person’s breathing rate is slower at rest – have a higher lung capacity.

• Breathing rate returns to normal faster in fitter individuals.

• If it falls below resting rate the person is breathing deeper.

• The faster the breathing rate after exercise, the longer it takes to return to normal.

Control – average resting breathing rate.

Application – A measure of a person’s fitness is an important measure of their general health. The fitter they are the stronger their lungs (and heart) will be and the more efficient their intake and distribution of oxygen and removal of CO2.

Biology bugbears

•

Bozemanscience AP Biology (Paul Anderson)

•

Leaving Cert questions

Section A

2019 HL Q6

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Section B

2014 HL Q9(b)

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2016 HL Q8

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Section C

SEC Sample Paper HL

13. (a) (i) Distinguish between breathing and respiration.

(ii) Breathing rate in humans is controlled by the concentration of a gas dissolved in blood. Which gas is this? (9)

(b) The diagram shows the human breathing system

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i) Name the parts labelled A, B, C, D, E.

ii) Where do cilia occur in this system? What is their function

iii) State precisely the events that take place at E. How is E adapted for these events? (27)

(c) Asthma and bronchitis are common disorders of the breathing system. Answer the following

in relation to one of these disorders. State the disorder to which you refer.

(i) State one possible cause of the disorder.

(ii) Suggest one way in which a person might adapt his/her lifestyle to minimise the

effects of the disorder.

(iii) Give an example of a treatment for the disorder. (24)

2007 HL Q13

13. (b) (i) Draw a large diagram of the human breathing system. Label the trachea, bronchus and lung.

(ii) State the function of the following: epiglottis, larynx.

(iii) Describe briefly the role of the diaphragm and intercostal muscles in inhalation.

In your answer refer to volume and thoracic air pressure.

(c) (i) Give three ways in which an alveolus is adapted for efficient gas exchange.

(ii) Name the process involved in the passage of gas between the alveolus and the blood.

(iii) Name a breathing disorder.

iv) In the case of the breathing disorder that you have named in (iii) state:

1. a cause,

2. a means of prevention,

3. a treatment. (24)

2009 HL Q13

13. (c)

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The diagram shows microscopic detail from a human lung.

i) Name the parts labelled A, B and C.

ii) Give two features of the structures in the diagram that allow for efficient gas exchange.

(iii) Name a disorder of the breathing system and say how it may be:

1. Caused.

2. Prevented.

3. Treated.

(iv) Which gas, dissolved in the blood, can trigger deeper or faster breathing?

2014 HL Q12

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2017 HL Q15(a)

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2021 HL Q16

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Leaving Cert answers

Section A

2019 HL Q6

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Section B

2014 HL Q9(b)

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2016 HL Q8

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Section C

2004 HL Sample Q13

|13. |(a) |(i) |Breathing is gas exchange. Respiration is the release of energy |2(3) |

| | |(ii) |Carbon dioxide |3 |

| |

| |(b) |(i) |A: bronchus, |5(2) |

| | | |B: trachea (allow cartilage), | |

| | | |C: larynx, | |

| | | |D: bronchiole | |

| | | |E: alveolus. | |

| | |(ii) |In the trachea/ nostrils. They move mucus upwards |2(3) |

| | |(iii) |At E oxygen diffuses into the blood/ CO2 diffuses out |2(3) |

| | | |E is adapted by being moist/ thin walled / has a large blood supply |3+2 |

| |

| |(c) |(i) |Asthma: Cause: pet dander/ allergens/ exercise |8 |

2007 HL Q13(b)(c)

| |

| |(b) |(i) |diagram [trachea, bronchus, alveoli, diaphragm or ribs] |6, 3. 0 |

| | | |[any one missing 3 marks] | |

| | | |labels [trachea, bronchus, lung] |3(1) |

| | |(ii) |epiglottis: to close off trachea or described |3 |

| | | |larynx: to make sound |3 |

| | |(iii) |diaphragm contracts / lowers / intercostal muscles contract / rib cage up/ #volume of chest |#2(3) |

| | | |(cavity) increased / #decreased pressure / air in / to equalise pressure [# points |2(3) |

| | | |compulsory] | |

| |

| |(c) |(i) |capillary network / moist surface / thin walled / elastic wall |3(3) |

| | | |[allow large surface area or one cell thick or thin membrane] | |

| | |(ii) |diffusion or passive transport |3 |

| | |(iii) |asthma or bronchitis |3 |

| | |(iv) |1. cause: |3 |

| | | |2. prevention: |3 |

| | | |3. treatment: |3 |

2009 HL Q13

| | |

| |(c) |(i) |A = Bronchiole |2 |

| | | | | |

| | | |B = Alveolus |2 |

| | | | | |

| | | |C = Arteriole or Capillary |2 |

| | |(ii) |Thin walled / moist surfaces / proximity (of alveoli and capillaries) / large surface area / large |Any two |

| | | |number (of alveoli or capillaries) |2(3) |

| | |(iii) |Named disorder |3 |

| | | | | |

| | | |1. Cause |2 |

| | | | | |

| | | |2. Prevention |2 |

| | | | | |

| | | |3. Treatment |2 |

| | |(iv) |*CO2 |3 |

2014 HL Q12

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2017 HL Q15(a)

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2021 HL Q16

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