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Human Biology Sylvia S. Mader Michael Windelspecht Chapter 9 Respiratory System Lecture Outline Part 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 9.5 Control of Ventilation How is breathing controlled by the nervous system? • Nervous control – Respiratory control center in the brain (___________________) sends out nerve impulses to contract muscle for inspiration. – Sudden infant death syndrome (SIDS) is thought to occur when this center stops sending out nerve signals. 2 9.5 Control of Ventilation How is breathing controlled by the nervous system? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. brain Respiratory center: region of the brain that automatically regulates breathing Intercostal nerves stimulate the intercostal muscles to contract. External intercostal muscles help expand the thoracic cavity by contracting. Phrenic nerve stimulates the diaphragm to contract. Diaphragm helps expand the thoracic cavity by flattening when it contracts. Figure 9.10 The control of breathing by the respiratory center. 3 9.5 Control of Ventilation How is breathing chemically controlled? • Chemical control – 2 sets of _______________ sense the drop in pH: one set is in the brain and the other in the circulatory system. – Both are sensitive to carbon dioxide levels that change blood pH due to metabolism. 4 9.6 Gas Exchanges in the Body Exchange of gases in the body • Oxygen and carbon dioxide are exchanged. • The exchange of gases is dependent on diffusion. • Partial pressure is the amount of pressure each gas exerts (PCO2 or PO2). • Oxygen and carbon dioxide will diffuse from the area of higher to the area of lower partial pressure. 5 9.6 Gas Exchanges in the Body External respiration • Exchange of gases between the lung alveoli and the blood capillaries. • PCO2 is higher in the lung capillaries than the air, thus CO2 diffuses out of the plasma into the lungs. • The partial pressure pattern for O2 is just the opposite, so O2 diffuses the red blood cells in the lungs. 6 9.6 Gas Exchanges in the Body External respiration Carbon dioxide transport: H+ + HCO3H2CO3 Oxygen transport: Hb + O2 carbonic anhydrase H2O + CO2 HbO2 7 9.6 Gas Exchanges in the Body The movement of oxygen and carbon dioxide in the body Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. alveolus plasma H+ + HCO–3 External respiration Hb H+ CO2 pulmonary capillary HCO–3 RBC H2CO3 CO2 Hb O2 H2O RBC O2 Hb CO2 pulmonary capillary O2 alveolus CO2 exits blood CO2 a. plasma O2 enters blood O2 lung pulmonary artery pulmonary vein heart tissue cells systemic vein systemic artery HCO–3 H+ + HCO–3 plasma plasma systemic capillary RBC Figure 9.11 Movement of gases during external and internal respiration. CO2 O2 RBC systemic capillary Hb H+ H2CO3 CO2 H2O Hb Internal respiration Hb CO2 tissue fluid CO2 enters blood b. tissue cell tissue cell tissue fluid O2 exits blood 8 9.6 Gas Exchanges in the Body Internal respiration • The exchange of gases between the blood in the capillaries outside of the lungs and the tissue fluid. • PO2 is higher in the capillaries than the tissue fluid, thus O2 diffuses out of the blood into the tissues. 9 9.6 Gas Exchanges in the Body Internal respiration Oxyhemoglobin gives up oxygen: HbO2 Hb + O2 Most CO2 is carried as a bicarbonate ion: CO2 + H2O carbonic anhydrase H2CO3 H+ + HCO3- 10 9.7 Respiration and Health Upper respiratory tract infections • __________ – blockage of sinuses • __________ – infection of the middle ear • Tonsillitis – inflammation of the tonsils • Laryngitis – infection of the larynx that leads to loss of voice 11 9.7 Respiration and Health Lower respiratory tract disorders • __________ – infection of the lungs with thick, fluid build up • __________ – bacterial infection that leads to tubercles (collections of encapsulated bacteria) • Pulmonary fibrosis – lungs lose elasticity because fibrous connective tissue builds up in the lungs, usually because of _______________ 12 9.7 Respiration and Health Lower respiratory tract disorders • _____________ – chronic, incurable disorder in which alveoli are damaged, and thus the surface area for gas exchange is reduced • Asthma – bronchial tree becomes irritated causing breathlessness, wheezing, and coughing • Lung cancer – uncontrolled cell division in the lungs that is often caused by smoking and can lead to death 13 9.7 Respiration and Health Some Diseases and Disorders of the Respiratory System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. mucus Pneumonia Alveoli fill with pus and fluid, making gas exchange difficult. Bronchitis Airways are inflamed due to infection (a cute) or due to an irritant (chronic). Coughing brings up mucus and pus. asbestos body tubercle Pulmonary Fibrosis Fibrous connective tissue builds up in lungs, reducing their elasticity. Pulmonary Tuberculosis Tubercles encapsulate bacteria, and elasticity of lungs is reduced. Emphysema Alveoli burst and fuse into enlarged air spaces. Surface area for gas exchange is reduced. Figure 9.12 Some diseases and disorders of the respiratory system. Asthma Airways are inflamed due to irritation, and bronchioles constrict due to muscle spasms. 14 9.7 Respiration and Health Things you should know about tobacco and health • All forms of tobacco can cause damage. • Smoking increases a person’s chance of lung, mouth, larynx, esophagus, bladder, kidney, pancreatic, stomach, and cervix cancers. • Smoking also increases the chance of chronic bronchitis, emphysema, heart disease, stillbirths, and harm to an unborn child. • Passive smoke can increase a nonsmoker’s chance of pneumonia, bronchitis, and lung cancer. 15