1. Human Breathing Chapter 31

2. Human Respiratory System: Consists of a pair of lungs and a series of tubes Lungs located in the thorax (chest) Diaphragm (sheet of muscle) forms the floor of the thorax Ribs (protective cage) and intercostal muscles (attached between ribs) form the walls of the thorax

4. Parts of the Respiratory System: PARTFUNCTION NostrilsAllows air to enter the nose NoseWarms, filters & moistens air Pharynx (throat)Connects nose & mouth to larynx EpiglottisFound in pharynx Stops food/drink entering trachea (windpipe) GlottisOpening to larynx

5. Larynx (Vociebox)Contains vocal cords Trachea ( windpipe)Allows air to pass to lungs *Made of muscle & elastic fibres with incomplete rings of cartilage CartilageStrong material which keeps trachea and bronchi open BronchiTransport air from trachea into lungs

6. BronchioleAbout 1 million per lung Transport air into the alveoli AlveoliThin walled, moist, surrounded by capillaries. Site of gas exchange, provides a large surface area (700 million in 2 lungs) for gaseous exchange LungTakes in O 2 and gets rid of CO 2 Pleural membranesAllow friction free movement of lungs

7. Diffusion is the movement of molecules from a region of high concentration to a region of lower concentration Remember: Gas Exchange

8. Gas Exchange in an Alveolus

9. Air enters the nose travels down the windpipe, the bronchus, and the bronchioles to the alveoli Oxygen diffuses from the alveoli to the red blood cells in the blood. At the same time carbon dioxide and water vapour diffuse from the blood (plasma) to the alveoli Note: in both cases CO 2 and O 2 are moving from areas of high concentration to low concentration.

10. Gas Exchange in Alveolus and Body Cell

11. Oxygen, carbon dioxide and water vapour diffuse in the reverse direction in the cells of the body: - Oxygen diffuses from the blood to the body cells - Carbon dioxide and water vapour diffuse out of the body cells and into the blood. (Note: cytoplasm of body cells has higher conc. of CO 2 & H 2 O than blood)

12. Adaptations to improve Gas Exchange Alveoli: have thin walls are very numerous are moist Capillaries: have thin walls are numerous

13. Inhaled Vs. Exhaled Air Note: - 97% oxygen transported by haemoglobin - Carbon dioxide & water vapour transported by plasma

14. Mechanism of Breathing Breathing (ventilation) is normally an involuntary process. The brain controls the rate of breathing This process has two stages: - inhalation/inspiration - exhalation/expiration

16.  The brain sends signals to the intercostal muscles and diaphragm to contract  The intercostal muscles contract and cause the rib cage to move up and out. At the same time the diaphragm flattens downwards.  The volume of the chest (thorax) increases, so air pressure drops. External air pressure is now higher than the pressure of air in the chest as a result more air is forced into the lungs and subsequently the alveoli. Inhaling requires energy as it is an active process i.e. energy required in movement of muscles Inhalation:

18. Exhalation:  There is no message so the intercostal muscles and diaphragm relax springing back to their original positions: - relaxed intercostal muscles cause rib cage to move down and in. - diaphragm moves up.  Volume of the chest decreases so air pressure increases, and air is forced out of the lungs. Exhaling does not require energy as it is a passive process i.e. muscles only have to relax

19. Effect of Exercise on Breathing Rate 100 75 50 25 225 175 125 75 5 mins10 mins15 mins20 mins RestExercise Breathing rate/min Recovery Heart rate/min

20. Effect of Exercise on Breathing Rate Adult at rest breathes approx 15 times/min. Exercise results in increased respiration Brain detects increased level of exercise and so increases breathing rate to allow for: - increase in oxygen inhaled (respiration) - increase in carbon dioxide exhaled (waste) Exhalation becomes an active process during exercise

21. Activity 19b: To investigate the effect of exercise on the breathing rate You have a choice to complete this activity or Activity 19a (pg. 266) – completed previously

22. Breathing Disorders You are required to study 1 breathing disorder!!! *Asthma – inflammation & constriction of bronchi Bronchitis Emphysema – destruction of alveoli TB – elasticity reduced (bacteria) Pneumonia – fills with fluid

23. Asthma: Asthma results in the narrowing of the lower bronchioles due to some irritant (dust mite, pollen, cold, virus) and so the sufferer finds it difficult to inhale enough oxygen Symptoms: Causes: coughing wheezing breathlessness chest tightness pollen animals smoke dust mites chemicals exercise

24. Prevention: Identify triggers – avoid or remove e.g. Allergens Treatment: Specific drug treatments which generally cause the bronchiole to widen e.g. Inhalers, steroids

25. Control Of Human Breathing Higher Level Only Breathing is under the control of the medulla oblongata in the brain, which is sensitive to CO 2 levels Nerve cells in the medulla are connected to the diaphragm and intercostal muscles

26. When CO 2 levels in the blood are high (as a result of increased respiration caused by exercise), the pH of the blood decreases This is detected by the brain and messages are sent to the intercostal muscles and diaphragm and the rate and depth of breathing is increased