BIPN 102 - 3/30/10 Respiratory System 2 diff types of...

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3/30/10 Respiratory System 2 diff types of respiration – one is cellular resp. which is carried out in mitochondria w ATP, but here we’re mainly concerned w external respiration so that’s what we’re going to call respiration. Respiratory system carries out a series of functions and has challenges due to the physics of the process. First, in terms of anatomy, the respiratory system, has to exchange air w the outside w air in the lungs, and that exchange is called ventilation . What is unique is that it’s a dead end so that air comes in in a certain path but must come out of the same pathway. This generates an obstacle which is dead space such that when air comes in, the air that occupies the airways, goes back in, and dilutes the air fresh that’s coming in. Conversely, when we expire, some air that’s in the airways with fresh air is the first one to come out. One of the challenges is how do we get air in and out. This requires muscle contraction which uses ATP and the fact that the lungs will need to b expanded. The challenge is how to be able to expand and utilize them w the minimal amount of energy. The next process is an exchange of gasses (O2 and CO2) btwn blood and this process involves diffusion. Know Fick’s law . So now from the gas phase, air has to dissolve in the blood and solubility is very low. The bubbles that come out are CO2 bc limited solubility in water, and solubility decreases as the temp increases. Solubility of CO2 is low but O2 is 20 times lower, so it’s a major challenge. Challenge is solved by making the gasses soluble in water. CO2 rxts with water to make carbonic acid and bicarbonate which are water soluble. O2 binds to hemoglobin which participates also in CO2 transport. The transport of gasses in the blood, at the level of the capillaries, we have the equivalent exchange btwn the tissue capillaries and the cells where CO2 and O2 go down their conc gradient to the mitoch. The heart participates in the sense where theres the systemic circ coming out of the L ventricle and the pulmonary coming out of the R ventricle. Pulmonary circ. Has all the cardiac output going to the lungs whereas systemic has cardiac output distributed to all of the body organs, so the pulmonary circ is faster than systemic circ bc the same volume has to trasverse the lungs in the same time. Challenge is matching the blood flow (Rate) w the diffusion of the gasses and in the pulmonary circ at rest, a red blood cell spends ¾ of a sec in the capillary which is the only place where gas exchange occurs. So diffusion must b fast enough (usually is) so that in ¾ of a sec, CO2 has equilibrated btwn the blood and alveolar air, and O2 has equilibrated btwn alveolar air and blood. When we excersice and cardiac output increases, (can increase to 25-35 L/min) and under those conditions, blood flow increases rapidly and there are only about 250 milliseconds for equilibration to occur. The processes which we match the diffusion and perfusion (Blood flow) are important. The pulmonary circ is a low P low resistance system compared to systemic circ bc the R ventricle onlyneeds to pump blood to top of
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BIPN 102 - 3/30/10 Respiratory System 2 diff types of...

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