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Lesson Notes on Respiration
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Chapter 10: Respiration
Students should be able to:
(a) Identify on diagrams and name the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries
(b) State the characteristics of, and describe the role of, the exchange surface of the alveoli in gaseous exchange
(c) Describe the removal of carbon dioxide from the lungs, including the role of the carbonic anhydrase enzyme
(d) Describe the role of cilia, diaphragm, ribs and intercostal muscles in breathing
(e) Describe the effect of tobacco smoke and its major toxic components - nicotine, tar and carbon monoxide, on health
(f) Define and state the equation, in words and symbols, for aerobic respiration in human
(g) Define and state the equation, in words only, for anaerobic respiration in human
(h) Describe the effect of lactic acid in muscles during exercise
10.1 Aerobic Respiration
10.1.1 Definition Breakdown of food substances in the presence of oxygen with the
release of a large amount of energy, with CO2 and water as the waste product
Reaction take place in mitochondria, with help of enzymes (Tissue Respiration)
10.1.2 Equation C6H12O6 + 6O2 6CO2 + 6H2O + Energy Glucose + Oxygen carbon dioxide + water + energy
10.1.3 Uses of energy in the human body Processes that require energy
o Production of proteinso Heartbeat, Muscular contractionso Active transporto Regulation of body temperature
10.2 Anaerobic Respiration
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10.2.1 Definition Breakdown of food substances in the absence of oxygen with the
release of a small amount of energy, with CO2 and ethanol as the waste product
Less efficient than aerobic respiration due to small energy released Certain microorganisms could depend entirely on it due to low
energy requirement to live
10.2.2 Equation C6H12O6 2C2H5OH + 2CO2 + Energy Glucose Ethanol + carbon dioxide + small amount of energy
Substantial amount of energy is still trapped within the chemical bonds of ethanol if ethanol is further broken down, more energy could be released
10.2.3 Anaerobic respiration in Man
Glucose Lactic acid + small amount of energy
Occurs when maximum aerobic respiration cannot release energy fast enough anaerobic respiration produce extra energy to meet the demand
Lactic acid builds up in the muscles causes fatigue Muscles incur an oxygen debt due to insufficient oxygen during
the course of vigorous contraction Lactic acid formation cause of muscular pain Normally goes on for short period of time Lactic acid is then removed to the liver during rest period
10.3 Gaseous Exchange in Man
10.3.1 Composition of inspired air (breathed in) and expired air (out) Inspired air Expired air
O2 21% 16.4%CO2 0.03% 4%N2 78% 78%
Water vapour Depends on external conditions SaturatedTemperature Depends on external conditions Body temperatureDust particles Depends on external conditions Very little
10.3.2 Respiratory System in Man
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Removed during rest
Some are oxidized release energy
Specialized Breathing movements enable rapid exchange of gases
10.3.3 Gaseous exchange surface of alveoli (External Respiration)
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Large surface area of alveoli provide large SA for gaseous exchange
10.3.4 Breathing mechanisms
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O2
CO2
Blood enters lungs (low O2, high CO2)Concentration gradient builds up from
1. Continuous flow of blood2. Breathing air in and out of
alveoli
High O2
Low CO2
O2, and CO2 diffuses across capillariesRapid diffusion helped by
1. One cell thick alveolar walls2. Presence of moisture on the
alveolar wall to enable O2 to dissolve in it
1. Hb + O2 HBO8
2. Reaction is reversible3. Direction is determined by O2
concentration
CO2 dissolve in plasma carried as hydrogen carbonate (HCO3
-) ions to lungs
In lungs, HCO3- CO2
CO2 diffuses out of capillaries into alveolar cavity
Water vapour evaporates from alveolar walls
Heat escapes into the alveolar air
Air enters from nostrils (lined with mucous membrane)
During Inhalation (Inspiration) External intercostals muscles contract
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Secrete mucus traps dust particles
Sweeps particles up the bronchi trachea larynx
Internal intercostals muscles relax
During Exhalation (Expiration) External intercostals muscles relax Internal intercostals muscles contract
10.4 Effect of tobacco smoke on health
Chemical Properties Effects on body
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Ribs swing upwards and outwards Sternum moves up Diaphragm contracts and flattens Thoracic cavity enlarges Air pressure in alveoli cause lungs to
expand Expansion of lungs reduce air
pressure in alveoli Alveolar air pressure < Atmospheric
air pressure Air rushes into lungs until air
pressure in lungs = atmospheric air pressure
Short pause for gaseous exchange
Ribs swing downwards and inwards Sternum moves down Diaphragm relax and arches upwards Thoracic cavity decreases Ribs and sternum press on the lungs Air is compressed and forced out
sNicotine Addictive drug
Causes release of hormone adrenaline
Makes blood clot easily
Increases heartbeat and blood pressure
Increased risk of blood clots in blood vessels
Carbon Monoxide
Haemoglobin + CO Carboxyhaemoglobin
Formation of carboxyhaemoglobin reduces the efficiency of oxygen transport of RBC
Increase rate of fatty deposits on inner arterial wall (atherosclerosis)
Damages lining of blood vessels
Can cause death if conc. of CO > 1%
Increased risk of atherosclerosis
Increased risk of thrombosis
Tar Contains carcinogenic chemicals (cancer-causing) which cause uncontrolled cell division
Paralyze the cilia
Blockage of alveoli and reduction in gas exchange efficiency
Dust particles trapped in mucus lining the airways cannot be removed
Irritant particles
Paralyze cilia lining air passages
Increased risk of chronic bronchitis and emphysema
10.4.1 Chronic Bronchitis Signs:
o Epithelium lining the airway becomes inflamedo Excessive mucus is secreted by the epitheliumo Cilia on the epithelium are paralyzed. Mucus and dust cannot be
removedo Airway become blocked breathing becomes difficulto Person has to cough persistently to clear his airway to breathe
increases chances of lung infections
10.4.2 Emphysema Signs:
o Persistent coughing cause walls between alveoli to break down
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o SA: Vol ratio decreaseso Lungs become inflated with airo Lungs lose their elasticityo Breathing becomes difficult person wheezes and suffer from
breathlessness
10.4.3 Lung Cancer Risk of getting lung cancer increases the more a person smokes
o Tar causes cells to divide uncontrollablyo Uncontrolled cell division leads to lumps of tissues being formed
Risks of getting other cancers are also greatly increased
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