5 The nasal passages and lungs Air is drawn into the body via the nose or mouth. There are advantages to breathing through your nose:the air is warmed so that it is closer to body temperaturetiny hairs and mucus in the nose filter the air, preventing larger dust and pollen particles reaching the alveolimucus moistens the air, making it easier for the alveoli to absorb.Air then travels through the larynx, trachea (windpipe), bronchi (one bronchus to each lung) and bronchioles to the alveoli, where oxygen passes into the bloodstream.
6 Mechanisms of breathing – inspiration When you breathe in:Intercostal muscles pull ribs up and outintercostal muscles between the ribs contract, pulling the chest walls up and outthe diaphragm muscle below the lungs contracts and flattens, increasing the size of the chestthe lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth.Diaphragm contracts and moves down
8 Mechanisms of breathing – expiration When you breathe out:Ribs move in and downIntercostal muscles between the ribs relax so that the chest walls move in and down.The diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest.The lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth.Diaphragm relaxes and bulges up
10 Gas exchange at the alveoli The alveoli are bunches of tiny air sacks inside the lungs.Each individual sack is called an alveolus.When you breathe in, they fill with air.The alveoli are covered in tiny capillaries (blood vessels).Gases can pass through the thin walls of each alveolus and capillary, and into the blood stream.Gases can also pass from the blood stream, into the alveolus.
12 Composition of inhaled and exhaled air GasAmount in inhaled airAmount in exhaled airOxygenCarbon dioxideNitrogenWater vapour21%Very small amount79%Small amount17%3%79%Large amountWhat are the main differences between inhaled and exhaled air?Ask the students to compare the relative amounts. Point out that:The amount of oxygen inhaled is greater than the amount of oxygen exhaled. Consider the efficiency of respiration at the cells.The amount of carbon dioxide is greater in exhaled air.The amount of nitrogen is the same.Mouth to mouth resuscitation works because there is still a lot oxygen left in exhaled air.Why does mouth-to-mouth resuscitation work?
13 Respiratory rate is how many breaths you take per minute. Measuring breathingTidal volume is the amount you breathe in and out in one normal breath.Respiratory rate is how many breaths you take per minute.Minute volume is the volume of air you breathe in one minute.Vital capacity is the maximum volume of air you can breathe out after breathing in as much as you can.Clarify and expand on the definitions with the studentsResidual volume is the amount of air left in your lungs after you have breathed out as hard as you can.
16 Calculating minute volume Remember:Minute volume is the volume of air you breathe in one minute.You can calculate a person’s minute volume by multiplying the volume of air they breathe in one breath, by their respiratory (breathing) rate.QuestionIf you breathe 14 times in one minute (respiratory rate) and you breathe 0.5 litres in each breath, what is your minute volume?Get students to calculate the answer before revealing it.Point out that at rest, the volume of air breathed in each breath will be the person’s tidal volume. During extreme exercise, it may be closer to their vital capacity.Answer:Minute volume = 14 × 0.5 litres= 7.0 litres
18 Breathing during exercise Muscle cell respiration increases – more oxygen is used up and levels of CO2 rise.The brain detects increasing levels of CO2 – a signal is sent to the lungs to increase breathing.Breathing rate and the volume of air in each breath increase. This means that more gaseous exchange takes place.The brain also tells the heart to beat faster so that more blood is pumped to the lungs for gaseous exchange.More oxygenated blood gets to the muscles and more CO2 is removed.
19 Breathing changes during exercise Look at these statistics for a 16 year-old athlete:During restDuring exerciseRespiratory rate14 breaths/ minute32 breaths/ minuteVolume per breath0.4 litres2.4 litresMinute volume?Calculate the athlete’s minute volumes during rest and exercise.Rest minute volume = 5.6 litresExercise minute volume = 76.8 litres
20 The effects of exercise on lung structures In the long-term, regular exercise strengthens the respiratory system.The respiratory muscles (the diaphragm and intercostals) get stronger, so they can make the chest cavity larger.This larger chest cavity means more air can be inspired, therefore increasing your vital capacity.More capillaries form around the alveoli, so more gaseous exchange can take place.Relate these facts to improvements in performance. Emphasise that lungs are NOT muscles and therefore do not increase in size – they function more efficiently.Gas exchange can now take place more quickly meaning exercise can be maintained at a higher intensity for longer.
21 respiration Respiration energy glucose oxygen Respiration is the process that takes place in living cells which releases energy from food molecules.Glucose from food is used to fuel exercise.Oxygen is required to ‘break down’ the glucose to produce energy. This energy is used to make muscles contract.respirationglucoseenergyoxygenWaste products, including carbon dioxide, are produced as a result of the chemical reactions. These must be removed and excreted.
22 Aerobic respiration There are two different types of respiration. When you exercise at a steady, comfortable rate, the cardiovascular system is able to supply the muscles with all the oxygen they need.Under these conditions, aerobic respiration takes place.carbon dioxideglucose+ oxygenenergy++ waterAerobic exercise can be maintained for long periods without the performer getting breathless or suffering muscle cramps. Moderate activities like walking, jogging, cycling and swimming use aerobic respiration.
24 Anaerobic respiration When you exercise at a high intensity, the cardiovascular system cannot supply enough oxygen to the muscles.Under these conditions, anaerobic respiration takes place.glucoseenergy+ lactic acidWith no oxygen available, glucose is burned to produce energy and lactic acid.Lactic acid is a mild poison. As it builds up, it causes muscle pain and eventually cramp.Short, intense activities like sprinting, weightlifting, jumping and throwing use anaerobic respiration.
27 Exam-style questionsDescribe the passage of oxygen from the nasal passages to the bloodstream.David goes jogging once a week for 45 minutes.David tries to increase his pace. He finds that he is forced to stop running and breathe hard for several minutes.List two differences between the air that David inhales and the air that he exhales while jogging.What two substances are used by David’s body cells to produce energy? What are the products of this reaction?From the nasal passages, the oxygen in the air passes the larynx, down the trachea, into the bronchi. It then passes through the bronchioles and into the alveoli. Oxygen passes through the semi-permeable walls of the alveoli, into the capillaries which cover the alveoli walls.a) There will be less oxygen, more carbon dioxide and more water vapour. b) Glucose and oxygen. The products are carbon dioxide and water. c) David had to stop because as exercise became more intense, his cardiovascular system could no longer supply his muscles with enough oxygen. Anaerobic respiration started, producing lactic acid. When the concentration of lactic acid in David’s muscles got too high, David was forced to stop and repay the oxygen debt. d) The body needs oxygen to neutralize lactic acid. Breathing hard after exercise also helps to get rid of any carbon dioxide that is left in the tissues.c) Explain why David had to stop.d) How did breathing hard help him to recover?
28 Can you remember all these keywords? LarynxTracheaBronchus / BronchiBronchiolesAlveoliDiaphragmIntercostal musclesOxygen uptakeTidal volumeRespiratory rateMinute volumeVital capacityResidual volumeAerobic respirationAnaerobic respirationOxygen debtLactic acid