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SL IB Biology II: Gas Exchange – Topic 6 & Option B I. Respiratory pathway or ventilation system (p.170) a. Nasal passages b. Throat/Pharynx c. Larynx/Voice Box d. Windpipe/ Trachea e. Bronchi i. Two tubes which leads into the lungs f. Lungs i. Superior lobe ii. Inferior lobe iii. Middle lobe (right lung only) g. Ventilation – process of inhaling and exhaling with oxygen entering the alveoli h. Gas exchange – process of exchanging one gas for the other between alveoli and capillaries (carbon dioxide for oxygen) i. Cellular Respiration – using oxygen for aerobic respiration (making ATP from glucose and oxygen) and creating carbon dioxide as a product II. Functions a. Process of gas exchange or ventilation system i. Mechanisms involving getting in oxygen from the air in lungs into the bloodstream & getting rid of carbon dioxide – maintaining concentration gradient in the alveoli III. Cleaning Air 1 a. You breath in millions of particles of foreign matter each day b. Prevention i. Passages are lined with ciliated cells that secrete mucus (nasal cavity, trachea, and bronchi) ii. Cilia constantly beat upward in the direction of your throat IV. Ventilation System a. Trachea Bronchus (bronchi) bronchioles alveoli i. Microscopic tubules (bronchioles) ii. Alveoli 1. Def: single layer of flattened cells shaped in a spherical shape a. increase total surface area (300 million alveoli in each lung) 2. Have a moist inner lining of alveolus a. allows for efficient diffusion 3. Surrounded by a dense networks of capillaries with a high concentration of carbon dioxide a. Respiratory gases do not have to diffuse far to reach single cell thick capillaries 4. Fxn: sacs of the lungs where oxygen and carbon dioxide are exchanged by diffusion between air in lungs and blood (Alveoli have a high concentration gradient of oxygen) 5. Alveoli in healthy lungs are elastic (stretch as you inhale and return to their original size as you exhale) 2 V. Mechanics a. Diaphragm and muscles between your ribs (internal & external intercostals muscles) enable you to breathe in and breathe out (muscles increase or decrease pressure in chest cavity) b. Diaphragm is located beneath the lungs and is a dome shape when relaxed c. Inhalation i. Diaphragm, abdominal muscles, & external intercostal muscles are contracting (diaphragm moves down and flattens when contracting) – internal intercostal muscles relax ii. All these events increase volume of the thoracic cavity – rib cage rises iii. The pressure inside the cavity decreases (partial vacuum) – less pressure pushing on the lung tissue iv. This partial vacuum draws air into the lungs from the mouth or nasal cavity to counter the partial vacuum within the lungs – fills alveoli with air d. Expiration i. Diaphragm, abdominal muscles, & external intercostal muscles relax (diaphragm becomes domed shaped when relaxed) – internal intercostal muscles contract ii. This decreasing the volume of the thoracic cavity – ribs drop down in chest cavity iii. The pressure inside the cavity increases forcing air out of the lung 3 VI. Control of Respiration a. Involuntary process b. Medulla oblongata = helps maintain homeostasis i. Responds to higher levels of carbon dioxide by sending nerve signals to rib muscles and diaphragm ii. Nerve signals cause these muscles to contract and you inhale VII.Training and the Pulmonary system a. Four processes i. Pulmonary ventilation – the movement of air into and out of the lungs ii. External respiration – gas exchange between the blood and air-filled sacs of the lungs iii. Transport of respiratory gasses – cardiovascular system is largely involved to move gases between the lungs and cells of the body iv. Internal respiration – gas change between the blood and body cells b. Lung volumes i. Ventilation rate – number of breaths a person takes each minute ii. Tidal volume – the volume of air that moves in or out with each inhalation or exhalation at rest 1. Measured by a spirometer iii. Vital capacity – the max volume of air that can be exhaled after max inhalation iv. Total lung capacity – the total volume of air in the lungs after a max inhalation 4 1. This includes vital capacity and residual volume (air left in the lungs after a vital capacity is exhaled) 2. can not be measured because that air is necessary to keep the structures of the lungs at least partially inflated during exhalation c. Oxygen consumption with Exercise i. Active muscle tissue consumes more oxygen & produces more carbon dioxide ii. Muscles can receive an inadequate supply of oxygen due to intense exercise – leads to anaerobic exercise. 1. this leads to increase lactic acid in muscles iii. Body needs a mechanism to ensure that the rate of transport of these respiratory gases meets the need of the increased demand iv. Medulla – breathing centre that increases ventilation a. Frequency & rate of breathing changes NOT mechanism (increase in tidal volume) d. Long-term Effect of training i. Larger vital capacity – development of stronger diaphragm and intercostals muscles. Volume of thoracic cavity is increased due to greater development of these muscles ii. Decrease in ventilation rate at rest – about 10% reduction because of increased vital capacity and capillary development around lung air sacs. 5 iii. Increase in max ventilation rate during exercise – about 10-15% increase 6