Grade 8 Respiration in Humans PDF

CHAPTER 07 Respiration |n Humans y :2 (2] CamScanner Chapter 7 | The Human Body - Maintaining Life Learning Outcomes « Define aerob...

CHAPTER 07 Respiration |n Humans y :2 (2] CamScanner Chapter 7 | The Human Body - Maintaining Life Learning Outcomes « Define aerobic respiration in human cells as the release of energy by the breakdown of glucose in the presence of oxygen and state the equation, in words and symbols. « Define anaerobic respiration in human cells as the release of energy by the breakdown of glucose in the absence of oxygen and state the word equation. « Explain why cells respire anaerobically during vigorous exercise resulting in an oxygen debt that is removed by rapid, deep breathing after exercise. When we are hungry, we can become weak and unable to function properly. We need food to give us energy. Our bodies digest the food and break it down into simpler substances which are used for various functions, including releasing energy. What happens to the glucose in our cells during energy release? Disciplinary [dea Energy Living organisms need energy to move, excrete, grow and reproduce. Since energy is stored Living organisms in food molecules such as glucose, living organisms release energy by consuming these rely on respiration to molecules and breaking them down through a process known as r=¢piration. release energy from the breakdown of carbohydrates. Energy There are two forms of respiration: aerobic and anaeroi: carbon + water amount of oxidation process, which dioxide energy. is a chemical reaction in which a molecule gains oxygen or loses The process is more complicated than the equation shown above. In reality, respiration is hydrogen. carried out in a series of steps that are catalysed by enzymes. The mitochondria in cells are the ‘factories’ that contain these enzymes. Thus, mitochondria play a vital role in aerobic respiration. Complex organisms, such as trees and humans, respire aerobically as they need large amounts of energy to survive. Some examples of energy-consuming processes in organisms are: synthesis of new protoplasm for growth and repair Link synthesis of proteins from amino acids active transport in the absorption of food substances by the small intestine Mitochondria are one muscular contractions such as heartbeats and respiratory movements of the many organclles inside our cells, Recall « transmission of nerve impulses what you have learnt in cell division Chapter 1. 128 @ CamScanner  Respiration in Humans | Chapter 7 During respiration, some energy is also released as heat. This heat is circulated around your body by the blood to keep you warm. What Is Anaerobic Respiration? Anaerobic respiration is the release of energy by the breakdown of » glucose in the absence of oxygen. Anaerobic respiration releases a relatively small amount of energy. In Muscle Cells During vigorous muscular contractions, your muscle cells respire aerobically at a high rate. You may start panting in order to remove carbon dioxide and take in oxygen at a faster rate. Your heart will also begin to beat faster so that the oxygen can be transported to your muscles at a faster rate. However, there is a limit to the increase in the rate of breathing and heartbeat. When vigorous activity continues, muscular contractions are so vigorous that maximum aerobic respiration is unable to release energy fast enough to meet the demand. If vigorous muscular contractions continue, energy demand increases. The muscle cells carry out anaerobic respiration to meet the increased energy demand. Lactic acid is formed in the process. The word equation for anaerobic respiration in human muscles is: | This process | releases a glucose -» lactic acid relatively small amount of energy. The small amount of energy released in anaerobic respiration, together with the energy released in aerobic respiration, helps the muscles to keep contracting. Since there is insufficient oxygen to meet the demands of the vigorous muscular contractions, the muscles are said to incur an oxygen debt. 1> Oxygen debt is the amount of oxygen requi red to remove lactic acid. @ CamScanner Chapter 7 The Human Body - Maintaining Life How Can Oxygen Debt (or Lactic Acid) Be Removed After a Race? 1 Continuation of fast heart rate This results in continued and fast transport of: + lactic acid from the muscles to the liver + oxygen from the lungs to the liver 2 Continuation of deeper and faster breathing This results in continued and fast intake of oxygen by the lungs. Sufficient oxygen is required to remove the lactic acid from the blood. Once the lactic acid is removed, the oxygen debt is repaid. Note that during a sprint event or a short distance race, the athlete obtains some of his or her energy from anaerobic respiration. This is because a lot of energy is needed during a short period of time. The oxygen supply to the muscles is insufficient for aerobic respiration to meet the energy demand. How Do We Study Respiration? Respiration in biology refers to cellular respiration, v/ is the release of energy when cells break down gluco in the presence of oxygen. It is different from breathi which refers to the process by which air moves in and the lungs. It is quite easy to check if someone is breathing However, it is harder to check for respiration. Thus, how do we study respiration? The process of respiration in humans is the same as in other organisms. Thus, plants, small animals and microorganisms are often used in experiments to investigate respiration. In aerobic respiration, oxygen is consumed while carbon dioxide, energy and water are released. Some of the energy released is in the form of heat. Therefore, if we can show that an organism consumes oxygen and gives off carbon dioxide and heat, we can say that it respires aerobically. Anaerobic respiration in humans is difficult to detect. This is because it does not require the consumption of oxygen and it may not produce carbon dioxide. However, microorganisms such as yeast do produce and give off carbon dioxide when they respire anaerobically. Therefore, if we can show that yeast gives off carbon dioxide in the absence of oxygen, we can say that it respires anaerobically. (%3 CamScanner  Respiration in Humans | Chapter 7 ~ Let's Investigate 7.1 Aim | To find out if carbon dioxide is given off during aerobic respiration | | Helpful Note | Procedure (a) | At the surface of a liquid, | 1 Set up the apparatus as shown in Figure 7.1. Potassium hydroxide solution is used molecules are constantly | to absorb carbon dioxide. Sodium hydroxide can also be used for this. Limewater is escaping from the liquid used 1o test the presence of carbon dioxide, which turns the limewater cloudy. as gas. Some may return 2 Use a suction pump to suck out the air through delivery tube E. This causes air to be to the liquid. As the drawn into flask A. The air flows through the apparatus as shown by the arrows. suction pump sucks out the air from flask D, it reduces the air pressure above the liquid surface. —>E ‘This leads to more gas to suction molecules escaping from pump the liquid in flask D. As air is continuously sucked out from flask D, a pressure difference is created between the potassium limewater snails limewater flasks, allowing air to hydroxide solution flow in the direction as Figure 7.1 shown by the arrows. Questions 1 What purpose does the potassium hydroxide solution in flask A and limewater in sk B serve? What happens to the limewater in flask D after some time? Explain your observation. You need to set up a control. What changes would you make to flask C for the control? v # your investigation uses a potted green plant, what precautions must you take? Explain your answer. Procedure (b) iternatively, we can use a hydrogencarbonate indicator, which can detect changes n carbon dioxide concentration. The colour changes in the indicator are shown in Figure 7.2. (— straw test-tubes hydrogencarbonate indicator control acidic gg—— neutral ——p> alkaline Figure 7.2 1 Set up the apparatus as shown in Figure 7.2. 2 Gently blow through the straw several times for 1 min. Question 1 What changes do you see in the two tubes after 1 min? Why? (%3 CamScanner Chapter 7 | The Human Body - Maintaining Life To study anaerobic respiration, yeast is used as a model organism. — Let's Investigate 7.2 Aim To find out if carbon dioxide is given off during fermentation (anaerobic respiration) Procedure 1 Add a few grains of dry yeast to some distilled water in a boiling tube. Stir well. 2 After 20 minutes, add an equal volume of boiled and cooled dilute glucose solution to the yeast suspension and mix well. 3 Add a little oil. 4 Connect the boiling tube to a test-tube containing limewater as shown in Figure 7.3. delivery boiling __| tube tube test-tube thin layer of oil g(;ucnse and yeast —| § suspension limewater Figure 7.3 Questions 1 Why do you need to boil the glucose solution before carrying o: the experiment? Link 2 What does the layer of oil serve as? Practical Workbook 3 What do you observe after some time? Explain your answer. Experiment 7A 4 What would you add to the boiling tube in a control experiment? |- Helpful Note Yeast (Figure 7.4) is a microorganism that respires aerobically in the presence of oxygen, but respires anaerobically in the absence of oxygen. In fermentation, yeast relcases ethanol (a type of alcohol) and carbon dioxide as waste products during anaerobic respiration. The ethanol produced still contains energy and this explains why only a small amount of energy is released in anaerobic respiration. Figure 7.4 Yeast cells 132 (%3 CamScanner  Respiration in Humans | Chapter7 ~ Let’s Practise 7.1 1 Why is respiration important to humans? 2 (a) Write the equations, in words and symbols, for aerobic respiration in humans. (b) Write the word equation for anaerobic respiration in human muscle cells. 3 Suggest two reasons why we need energy when we sleep. 4 Four test-tubes are set up as shown in Figure 7.5. All the tubes contain the same amount of neutral indicator (red) and are left in sunlight for one hour. indicator indicator T solution solution | snail - —— snail water plants B C D acidic neutral alkaline Figure 7.5 (a) What colour change would you expect to occur in tube A and tube B? Why? (b) If the colour of the indicator in tube C does not change, what explanation can you give? (c) Would you expect the indicator in tube D to change colour? Why? 5 Figure 7.6 shows the apparatus used to graduated capillary investigate respiration. tube (cm?) (a) What can be measured using the apparatus shown? coloured (b) What is the purpose of the sodium droplet hydroxide solution?. () Inwhich direction will the coloured nsectlanva droplet move as the insect respires? __:a:e,: i (d) Explain your answer in (c). sodium i Link [~ hydroxide Theory Workbook Figure 7.6 ‘Worksheets 7A-7B — e i s @ CamScanner  Learning Outcomes. Identify the larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries and state their functions in human gaseous exchange.. Explain how the structure of an alveolus is related to its function of gaseous exchange, including describing the role of the cilia, greathing and life are intimately connected. In many languages, the same word is used for breath’ and ‘spirit’. We usually check for breathing to determine if someone is still alive. If yo, try to hold your breath, after a certain time, your body fights to breathe again. Your body is programmed to keep breathing. Why is breathing so important? How Do Organisms Take In Oxygen for Aerobic Respiration? Organisms take in oxygen for aerobic respiration through the process of gas exchange. » Gas exchange is the exchange of gases between an organism and the environment. Unicellular organisms, such as amoebae, have a large surface area-to-volume ratio. Such organisms do not require any special gas exchange system or oxygen transport mechanisms. Oxygen and carbon dioxide can be exchanged efficiently between the organism and the surrounding water by diffusion through the cell membrane. Large animals, such as fish, amphibians and mammals, have a comparatively smaller surface area-to-volume ratio. Their external surfaces are often thickened for protection and to prevent water Joss. Therefore, these surfaces are not suitable for gas exchange. These animals use special organs, such a5 lungs and gills, for gas exchange. These organs have enlarged surface areas and thin coverings. In this way, more oxygen can be absorbed and more carbon dioxide Figure 7,7 Frogs have lungs and removed from the body per unit time. permeable skin for gas exchange. In humans, the absorption of atmospheric oxygen and the removal of carbon dioxide from the body occur in the alveoli (air sacs) in the lungs. The Human Gas Exchange System The organs involved in gas exchange in humans are shown in Figure 7.8 on the next page. They include the two lungs in the thorax and the air passages leading to them. The air passages consist of the nasal passages, pharynx, larynx, trachea, bronchi and bronchioles. The thoracic cavity, ribs, diaphragm and related muscles are also vital parts of the gas exchange system, and their functions will be discussed in Section 7.3, which covers the breathing mechanism in humans. @ CamScanner  Respiration in Humans | Chapter 7 nasal passage external nostl C-shaped ring of cartilage cut end of nb bronchy cluster of alveoli “* i sacs) [— thorax internai intercostal muscle lung diaphragm Figure 7.8 The human gas exchange system The Nose Air usually enters your body through the two external nostrils. The walls of the nostrils bear a fringe of hairs. The nostrils lead into two nasal passages, which are lined with a moist mucous membrane. Breathing through the nose has the following advantages: - Dust and foreign particles, including bacteria in the air, are trapped by the hairs in the nostrils as well as by the mucus on the mucous membrane, As air passes through the nasal passages, it is warmed and moistened. @ Harmful chemicals?flay be detected by small sensory cells in the Disciplinary Idea mucous membrane. System The respiratory system comprises various organs From the Nose to the Trachea s acilitate gaseots The air in your nasal passages enters the pharynx. From the pharynx, air exchange. passes into your larynx and then into your trachea through an opening. 135 (2] CamScanner  ~napter7 | The Human Body - Maintaini ng Life Trachea The trachea (windpipe) is supported by C-shaped rings of cartilage (Figure 7.9). The cartilage keeps the lumen of the trachea open. The membrane next to the lumen is the epithelium. The epithelium consists of two types of cells.. Gland cells — secrete mucus to trap dust particles and bacteria. Ciliated cells — have hair-like structures called cilia on their surfaces. The cilia sweep the dust-trapped mucus up the trachea. mucus produced by gland cell gland cell To pharynx (throat) larynx C-shaped ring trachea of cartilage Section taken from here ligament From lungs @ | nucleus of cilia cytoplasm epithelial cell connective tissue lumen cell membrane (cavity in thin et C-shaped ring trachea) of cartilage Epithelium enlarged Transverse section (T.5.) of trachea Figure 7.9 Features of the air passages Bronchi and Bronchioles The trachea divides into two tubes called bronchi (singular: bronchus). Each bronchus carries air into the lung. The bronchi are similar in structure to the trachea. Each bronchus branches repeatedly, giving rise to numerous bronchioles. Bronchioles are very fine tubes. Each bronchiole ends in a cluster of air sacs or alveoli. Alveoli (Air Sacs) Gas exchange takes place through the walls of the alveoli (Figure 7.10). Numerous alveoli are found in the lungs, providing a very large surface area for gas exchange. 136 (%3 CamScanner  Respiration in Humans | Chapter 7 cutend of rib cluster of alveoli bronchioles lung diaphragm airin and out Tl blood vessel to heart pulmonary vein } pulmonary artery j capillary network. Alveolar walls are very thin, moist and well-supplied with blood capillaries. Gas exchange between the alveoli and the blood capillaries takes place through the wall of the alveoli. Figure 7.10 The lungs showing a clusterof alveoli and its associated capillaries How Are the Lungs Adapted for Efficient Gas Exchange? « The numerous alveoli in the lungs provide a large surface area. « The wall of the alveolus is only one cell thick. This provides a short diffusion distance for gases, ensuring a higher rate of diffusion. Word Alert « Athin film of moisture covers the inner wall of the alveolus. This allows oxygen to dissolve in it. Alveolus: singular of alveoli « The walls of the alveoli are richly supplied with blood capillaries. The flow of blood maintains the concentration gradient of gases. 137 (2] CamScanner  Chapter 7 | The Human Body - Maintaining Life How Does Gas Exchange Occur in the Alveoli? | Lin Gas exchange in the lungs occurs by diffusion. Blood entering the lungs | Diffusion requires a has a lower concentration of oxygen and a higher concentration of | concentration gradient carbon dioxide than the atmospheric air entering the alveoli in the lungs. Recall what you have A concentration gradient for oxygen and carbon dioxide is set up between | learnt in Chapter 2 blood and alveolar air (Figure 7.11). & —— + Oxygen dissolves into the thin film of moisture on the wall of the alveolus. + The dissolved oxygen then diffuses through the wall of the alveolus and the wall of the blood capillary into the red blood cells. + The oxygen combines with haemoglobin to form oxyhaemoglobin.. Carbon dioxide diffuses from the blood into the alveolar air. thin film of —» oxygen moisture carbon dioxide.l alveolar wall [[] oxygenated blood (one cell thick) Disciplinary Idea [] deoxygenated blood Structure and continuous z blood flow Function The structure of the alveli is designed to allow efficient gas exchange in humans. Figure 7.11 A section of an alveolus The oxygen and carbon dioxide concentration gradients bet airand the blood are maintained by: « a continuous flow of blood through the blood capillaries | - continuous breathing, which causes air in the lungs to be constantly | ! refreshed 1 How Is Oxygen Transported Around ‘ the Body? | In the lungs where the oxygen concentration is high, oxygen combines with haemoglobin in the red blood cells to form oxyhaemoglobin. Oxygenated | blood is transported from the lungs to other parts of the body. | | high oxygen concentration oxygen + haemoglobin 7 > oxyhaemoglobin low oxygen concentration When blood passes through an organ or tissue where the oxygen concentration is low, oxyhaemoglobin will release its oxygen to the respiring cells. 138 @ CamScanner  Respiration in Humans | Chapter 7 How will oxygen transport in a person's body be affected if he holds his breath for a long time? Comment on the views given by the three people in Figure 7.12. Explain why each of them is correct or incorrect. The red blood cells There is no problem travelling over the alveoli will not i 7[”'! heari :’, d for the red blood cells to “:::/',:::; ':z:flno/m ,,':J,':’.f:., i will still pump bloo transport oxygen to other cells, will run out of ‘oxygen and may throughout the body. So, there but the heart will beat slower fall, starting with is no problem for the red blood as there is less oxygen ’the brain. cells to transport oxygen to in the body. < » other cells. Rt Le 1 Name the parts labelled A to G in Figure 7.13. 2 Figure 7.14 shows some cells from the lining of a human trachea. (a) Name the parts labelled A, B and C. (b) The diagram is incomplete. Complete it by drawing the cilia that should be found on the cells. Your drawing should show the & direction in which the cilia are sweeping. (c) What is the name of the substance that the gland cells secrete? Link (d) Based on your understanding of the function of the cilia, what Theory Workbook would happen if they were paralysed? Workshect 7C —> to pharynx (throat) substance secreted by gland cell gland cell Figure 7.14 Cells lining the human trachea Figure 7.13 139 @ CamScanner  Chapter 7 | The Human Body - Maintaining Life Learning Outcome. Describe the process of breathing and the role of diaphragm, ribs and internal and exte,, | intercostal muscles. | Have you ever seen opera singers sing a very long note without pausing for breath? Do yoJ wonder how they can take in so much air and control the breath? It is all due to the highl, trained muscles of their breathing mechanism. Yes, breathing is an activity that involves muscles, and it can be trained. | | Breathing is part of the gas exchange process. It refers to the muscular contractions and movements of the ribs, which result in air moving in and out of the lungs. Humans possess ‘ special breathing mechanisms that increase the rate of gas exchange between the body zn: the external environment. The breathing movements essentially consist of two phases: « The taking in of air called inhalation or inspiration.. The giving out of air called exhalation or expiration. The Thoracic (Chest) Cavity The chest wall is supported by the ribs. Between the ribs, two sets of muscles, the external and internal intercostal muscles, can be found (Figure 7.15). They are antagonistic muscles This means that when the external intercostal muscles contract, the internal intercostal muscles relax, and vice versa. vertebral column {oackbone) external intercostal muscles sternum, (chest bone) internal intercostal muscles left lung (intercostal muscle Chest X-ray showing the ribs and s removed to show the left lung) Figure 7.15 The ribs and the intercostal muscles 140. d @ CamScanner  Respiration in Humans | Chapter 7 The thorax is separated from the abdomen by a dome-shaped sheet called the diaphragm. The diaphragm is made of muscle and elastic tissue. When the diaphragm muscles contract, the diaphragm flattens downwards, and when they relax, the diaphragm arches upwards again. The workings of the Link intercostal muscles and the diaphragm change the volume of the thoracic Refer to Figure 7.8 in cavity (Figures 7.16 and 7.19). Section 7.2 to recall the position of the thorax Inspiration (Inhalation) Note that the words ‘upwards’ and ‘downwards’ are used with reference to a person standing in the upright position. When you inspire, the following events take place: Your diaphragm muscle contracts, and the diaphragm flattens. Your external intercostal muscles contract while your internal intercostal Word Alert muscles relax. Inspire: Inhale, Your ribs move upwards and outwards. Your sternum also moves up and breathe in forward. - The volume of your thoracic cavity increases. Your lungs expand and air pressure inside them decreases as the volume increases.. Atmospheric pressure is now higher than the pressure within your lungs. + Air moves into the lungs. J— vertebral 0 T column airforcea e during ~2.' _ - _ Increase in voi e inspiration position during Handle of the pail expiration shows how a rib move up external is raised during and forward R/ volume intercostal of thorax sternum muscles inspiration increases contract vertebral column diaphragm sismum Figure 7.17 A model showing flattens the movement of the ribs rib during breathing Side view | muscle of diaphragm contracts Ribs move upwards and outwards to increase the Figure 7.16 Movement of rib cage volume of thorax and diaphragm during inspiration diaphragm flattens Front view The path of the air into the lungs is shown below: external =¥ nasal — pharynx — larynx — trachea — bronchi — bronchioles — alveoli nostrils passages 141 @ CamScanner  Chapter7 | The Human Body - Maintaining Life Model to Show How Breathing Works Figure 218 shows a model that Is used to demonstrate the action of the diaphragm. When the rubber sheet (diaphragm) is pulled down, the increase in volume causes a drop in the air pressure inside the bell jar. Atmospheric pressure outside is now higher than that in the jar. This forces air to enter and fill up the balloons (lungs). qlass tube (trachea) qlass tube bronchus) balloon (lung) ’ bell jar / (thoracic wall) Word Alert Expire: exhale, breathe out i o rubber sheet ! (diaphragm) Helpful Note RICE and ERIC Figure 7.18 Model showing the actions of the diaphragm in the Here is an easy way to human gas exchange system remember what happens to your intercostal muscles | when you are breathing. Expiration (Exhalation) When you inhale, you... When you expire, the following events take place: Relax your + Your diaphragm muscle relaxes and the diaphragm arches upwards. Internal intercostal « Your internal intercostal muscles contract while your external | muscles and intercostal muscles relax. | Contract your + Your ribs move downwards and inwards. Your sternum also moves ‘. External intercostal down to its original position. ‘ muscles, + The volume of your thoracic cavity decreases. || When you exhale, your... + Your lungs are compressed and air pressure inside them increases as i| External intercostal the volume decreases, muscles « Pressure within the lungs is now higher than atmospheric pressure. Relax and your Internal intercostal The air is forced out of your lungs to the exterior environment. muscles Contract. 142 @ CamScanner  Respirationin Humans | Chapter 7 air forced out of lungs due to decrease in volume of lungs ribs and sternum move down to original volume position \ of thorax decreases vertebral column diaphragm sternum arches upwards rib diaphragm muscle refaxes Side vin ~ibs move downwards and inwards to decrease the diaphragm Figure 7.19 Movement of rib cage and volume of thorax arches diaphragm during expiration upwards Front view Tech Connect A mechanical ventilator is a machine that can pump air into a person's lungs, just like when one breathes in. It can also pump air out of the lungs, just like when one breathes out. During the COVID-19 pandemic, ventilators were in high demand in hospitals. Patients with inflamed airways due to the Covid-19 virus experienced breathing difficulties. Doctors had to put them on ventilators to help them breathe. These important pieces of technology have saved the lives of many seriously ill patients during the pandemic. Figure 7.20 A mechanical ventilator helps patients to breathe. 143 @ CamScanner  Chapter7 | The Human Body - Maintaining Life How Does Inspired Air Differ from Expired Air? Word Alert Inspired air differs in composition from expired air. Some water evaporates Inspired: inhaled from the surfaces of the alveoli. This explains why the air we breathe out Expired: exhaled is saturated with water vapour. In the lungs, oxygen has been absorbed into the bloodstream, but carbon dioxide is released from the blood. This explains why the air we breathe out has a lower oxygen concentration but a higher carbon dioxide concentration than the air we breathe in. Some heat also escapes from the blood into the alveolar air. The differences between inspired and expired air are summarised in Table 7.1. Table 7.1 Differences between inspired and expired air Component Inspired Air Lower Higher Helpful Note !Aba‘ufthehme' ~ Aboutthesame Expired air contains about 16.4% of oxygen. vVan.able (rarely saturated) Saturated Not all_ |h§ _oxyge; that W‘fifib‘q but usually present Little, if any ‘fi:r;sel::iemliso:,“ Temperature Variable About body temperature (37 °C) Figure 7.21 Composition of inspired and expired air (refer to Table 7.1 for colour codes) Inspired air Eghedan The differences between inspired and expired air can be investigated by carrying out the following experiments. Let's Investigate 7.3 Aim To find out if the amount of carbon dioxide in inspired air is different from expired air Procedure 1 Fit two conical flasks, containing about the same volume of limewater, with glass tubings as shown in Figure 7.22. 144 @ CamScanner  Respirat in Humans ion | Chapter? 2 Place the open end of the T-tube in your mouth, Gently breathe aif in \ and out through your mouth. As air is breathed in, atmospheric alr (i.e. | inspired air) is drawn into tube C. It bubbles through the limewater in i flask A and up through tube D into the mouth, When air is breathed \ out, the expired air passes through tube E and into the limewater in | flask B and out into the atmosphere through tube F. T-tube placed in mouth rubber tubes limewater Figure 7.22 Investigating the amount of carbon dioxide in inspired and expired air &2 Questions Link + rinutes, what do you observe in the two flasks? Practical Workbool +canclude from this investigation? Experiment 7B — e 7.4 N Aim To find out if the temperature of inspired air is different from that of expired air Procedure 1 Use a thermometer to determine the temperature of the room. 2 Then, hold the bulb of the thermometer close to your mouth and breathe air onto it continuously. Record the temperature of the expired air. Question. 1 Which has a higher temperature, inspired or expired air? _., @ CamScanner Chapter 7 | The Human Body - Maintaining Life Helpful Not How Much Air Do We Breathe In and Out of the Lungs? ~ Volume of air in Only some of the air in your lungs is changed ip each lungs/ cm? breathing cycle (Figure 7.23). The amount of air changed 5000 fommmmmm g = ——— IR S varies with the depth of breathing. It has been estimated that in each normal breathing cycle, about 500 cm” of air complemental air enters the lungy, and about the same volume is breathed out. This volume of air is known as tidal air. 3500 vital capagy, 3000 When you take a deep breath, you take in a volume of air that is larger than your tidal air. The additional volume of air i called the complemental air and it is about 1500 em*. Similarly, about 1500 cm’ can be forced out after normal 1500 el e eS e Feeel expiration. This is called supplemental air. residual air Take the deepest breath you can, then blow out all the air you can. The total volume of air exhaled during forced 0 Time exhalation is about 3500-4000 cm’. This is the vital capacity of the lungs. Figure 7.23 Graph showing the amount of air in the lungs during breathing vital capacity= tidal air + complemental air+ supplemental air No matter how hard you try to force all the air out of your lungs, there will always be some left behind. This volume of air, estimated to be about 1500 cm", is called residual air. — Let's Practise 7.3 1 A spirometer is an instrument used to measure the volume of air that enters and leaves the lungs during breathing. In an experiment, a man was at rest for one minute and then exercised for one minute. His rate of breathing was recorded in Figure 7.1 (a) How many breaths per minute was the man taking while as.~ (b) How much air was taken into his lungs during the one-mis...: rest? (€) What changes took place in his breathing during exercise? (d) Which part of the graph, A or B, represents expiration? Volume of air / dm? Link T T T T Time/s Theory Workbook 30 60 60 120 Worksheet 7D Figure 7.24 146 (%3 CamScanner  Respiration in Humans | Chapter 7 Learning Outcome. State the major toxic components of tobacco smoke — nicotine, tar and carbon monoxide, and describe their effects on health. Cigarette manufacturers used to spend a huge amount of money for cigarette sdvertisement on media such as TV and billboards. They paid powerful influencers such as celebrities to show how smoking was cool and trendy. Today, we hardly see any cigarette advertisements. What has changed? As more and more medical evidence emerged to show the harmful effects of smoking on health, restrictions were imposed over the last 50 years. In Singapore, smoking is banned in most public spaces and forbidden for those under a certain age limit. Instead of cigarette advertisements, you will see more quit-smoking campaigns. Why is smoking now considered bad? Tobacco smoke contains more than 4000 chemicals, most of which are harmful to the body. Figure 7.25 lists some of the components that have been linked to health problems. inTobacco « Itincreases heartbeat rate and blood pressure. Smoke « Itincreases the risk of blood clots in the arteries, which leads to increased risk of coronary heart disease. = Nicotine Itincreases the risk of arteries to narrow. - In a pregnant mother, narrow arteries decrease the amount of food substances reaching the fetus, thereby affecting fetal ’\ development and may cause miscarriage. It reduces the ability of blood to transport oxygen as carbon monoxide binds permanently with haemoglobin. Thus, there __, Carbon will be less haemoglobin available to transport oxygen. monoxide - In a pregnant mother, less oxygen reaches the fetus through the placenta which may affect fetal development. Itincreases the risk of coronary heart disease. It increases the risk of cancer in the lungs as tar can cause uncontrolled cell division. ——eTar It increases the risks of chronic bronchitis and emphysema. - Tar paralyses the cilia lining the air passages. Hence, dust particles trapped in the mucus lining cannot be removed. Figure 7.25 Chemicals in tobacco smoke and their harmful effects 147 Chapter7 1| The Human Body - Maintaining Life What Diseases Are Caused by Tobacco Smoke? Frequent exposure to tobacco smoke increases the risk of a person getting diseases of the respiratory system, such as chronic bronchitis, emphysema and lung cancer. The World Health Organisation (WHO) estimates that more than 8 million people die each year due to tobacco use. Chronic Bronchitis Prolonged exposure to irritant particles that are found in tobacco smoke may cause chronic bronchitis. In chronic bronchitis: The epithelium lining of the air passages (airways), for example, the bronchi, becomes inflamed. Excessive mucus is secreted by the epithelium. The cilia on the epithelium are paralysed. Mucus and dust particles cannot be removed. The air passages become blocked, making breathing difficult. In order to breathe, persistent coughing occurs to clear the ‘ air passages (Figure 7.26). This increases the risk of getting lung infections. Figure 7.26 Emphysema Chronic bronchitis Persistent and violent coughing due to bronchitis may lead to may cause a emphysema. In emphysema: smoker to cocugh « The partition walls between the alveoli break down due to persistent persistently. and violent coughing (Figure 7.27). « This results in a decreased surface area for gaseous exchange « The lungs lose their elasticity and become inflated with air « Breathing becomes difficult. Wheezing and severe breathlessnes When a person has chronic bronchitis and emphysema, he 15 531 from chronic obstructive lung disease. partition freae ged , betweenwallsair — partition: Lot 5h sacs (alveoli) Healthy lung Damaged lung Figure 7.27 Diagram showing a healthy lung damaged by emphysema Lung Cancer Studies have shown that the risk of lung cancer increases when a person smokes tobacco. Figure 7.28 shows the lungs of a smoker compared to a pair of healthy lungs. According to the Singapore Health Promotion Board, smoking-related diseases in Singapore alone accounts for about seven premature deaths each day. Cancer is the uncontrolled division of cells producing outgrowths or lumps Aguie7.28 of tissues. Apart from lung cancer, smoking also increases the risk of ::zzl)l::;ungfi cancers of the mouth, throat, pancreas, kidneys and urinary bladder smoker’s lungs (bottom) Link Let's Practise 7.4 Theory Workbook 1(a) Name three harmful chemicals found in cigarette smoke Worksheet 7E (b) State the effects of these chemicals on the body. 2 Describe how smoking can lead to chronic bronchitis. 148 @ CamScanner  Respiration in Humans | Chapter 7 Let's Map It Respiration ENERGY. Lo Involves the breakdown of food molecules to release energy « Occursin living cells « Involves enzymes - CH,,0,+60, canoccuras | v 1 | Aerobic respiration Anaerobic respiration ' glucose + oxygen —- carbon dioxide + water glucose =+ lactic acid | CHO, + 60, - 6CO, +6HO « Oxygen is not required + Oxygen is required + Small amount of energy is released + Large amount of energy is released « Lactic acid is produced in humans + Carbon dioxide and water are produced P supportedby % Breathing mechanism in humans h ~ R | involves | s | Inspiration (Inhalation) | Expiration (Exhalation) + External intercostal muscles contract, - Internal intercostal muscles contract, internal intercostal muscles relax external intercostal muscles relax « Ribs move upwards and outwards - Ribs move downwards and inwards + Diaphragm contracts and flattens - Diaphragm relaxes and arches upwards | | * Volume of thorax increases « Volume of thorax decreases | + Air pressure in lungs decreases « Air pressure in lungs increases ; + Air enters the lungs + Airis forced out of the lungs [ leadto 15 offected Gas exchange ) by « Oxygen dissolves in the film of moisture covering the alveolar wall + Dissolved oxygen diffuses into the blood capillaries | « Carbon dioxide diffuses from blood into the alveolar cavity | l ' increases | Tobacco contains | - Nicotine risk of « Chronic bronchitis " smoke « Carbon monoxide « Emphysema « Tar « Lung cancer 149 (2] CamScanner  Chapter7 | The Human Body - Maintaining Life Section A: Multiple-choice Questions 2 Figure 7.29 shows part of the respicy, systemn, \: 1 Which changes occur in the blood branch of the: » as it flows through muscles during a pultnonary —— ; vigorous attivity? Blood Concantration of Temperature | LacticAcidin Blood ] Increases Increases B Increases Decreases (4 Decreases Increases D Decreases Decreases 2 When a person is resting, the amount of oxygen in his expired air is Figure 7.29 A higher than that in his inspired air. (a) Name the structures labelled 4,3 and C. L B.lower than that in his inspired air. (b) What is the difference in the € higher than that in his expired air amount of when he is exercising. (i) carbon dioxide, 2 the same as the amount of oxygen (ii) oxygen n the air, in the blood at X as comparedto iy B: Structured Questions Section C: Free-response Questions State two similarities between 1 What do you understand by the aerobic and anaerobic respiration. term oxygen debt? tiz; State three differences between aerobic and anaerobic respiration. 2 In what ways are the lungs adaptedt the efficient absorption of oxygen? 2 (a) During a 100 m race, the energy that the athlete uses comes from 3 How does expired air differ from both aerobic and anaerobic inspired air? Suggest reasons for the respiration. Explain why. differences. (b) Write down the word equation for anaerobic respiration in muscles. 4 Suggest reasons why gas exchangei less efficient in the lungs of a person with emphysema. @ CamScanner