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Human Breathing Chapter 31 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 Parts of the Respiratory System: PART Nostrils Nose Pharynx (throat) Epiglottis Glottis FUNCTION Allows air to enter the nose Warms, filters & moistens air Connects nose & mouth to larynx Found in pharynx Stops food/drink entering trachea (windpipe) Opening to larynx Larynx (Vociebox) Contains vocal cords Trachea ( windpipe) Allows air to pass to lungs *Made of muscle & elastic fibres with incomplete rings of cartilage Cartilage Strong material which keeps trachea and bronchi open Bronchi Transport air from trachea into lungs Bronchiole Alveoli About 1 million per lung Transport air into the alveoli Thin walled, moist, surrounded by capillaries. Site of gas exchange, provides a large surface area (700 million in 2 lungs) for gaseous exchange Lung Takes in O2 and gets rid of CO2 Pleural membranes Allow friction free movement of lungs Gas Exchange Remember: Diffusion is the movement of molecules from a region of high concentration to a region of lower concentration Gas Exchange in an Alveolus 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 CO2 and O2 are moving from areas of high concentration to low concentration. Gas Exchange in Alveolus and Body Cell 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 CO2 & H2O than blood) Adaptations to improve Gas Exchange Alveoli: • have thin walls • are very numerous • are moist Capillaries: • have thin walls • are numerous Inhaled Vs. Exhaled Air Note: - 97% oxygen transported by haemoglobin - Carbon dioxide & water vapour transported by plasma 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 Inhalation: 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 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 Effect of Exercise on Breathing Rate Breathing rate/min Heart rate/min 225 Rest Exercise Recovery 100 175 75 125 50 75 25 5 mins 10 mins 15 mins 20 mins 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 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 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 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: • coughing • wheezing • breathlessness • chest tightness Causes: • pollen • animals • smoke • dust mites • chemicals • exercise Prevention: Identify triggers – avoid or remove e.g. Allergens Treatment: Specific drug treatments which generally cause the bronchiole to widen e.g. Inhalers, steroids Control Of Human Breathing Higher Level Only • Breathing is under the control of the medulla oblongata in the brain, which is sensitive to CO2 levels • Nerve cells in the medulla are connected to the diaphragm and intercostal muscles • When CO2 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