Pulmonary Ventilation cellular metabolism The respiratory system is responsible for the movement of gasses involved in Oxygen is used up and carbon dioxide is generated during the aerobic breakdown of glucose and other fuel molecules in order to produce ATP 2 important physiological process responsible for the movement of oxygen and carbon dioxide o 1 Ventilation o 2 Gas Exchange Moves gases in and out of the lungs The movement of gases into and out of the blood Occurs at the lungs external respiration and at the tissues internal respiration o 3 Gas Transport throughout the body systemic circulation Blood gases Blood gases are transported to the lungs pulmonary circ are transported to the organs and tissues Ventilation phases o The process of bringing air into and out of the lungs Inspiration Expiration air moves into the lungs air moves out of the lungs o Proper ventilation is important to promote airflow which enhances gas exchange Ventilation driving forces o Direction of airflow is determined by changing pressures o Air flows from high to low pressure o Pressure can be altered by changing the volume Pressure volume relationship the direction of airflow o Changing the relative pressure in the compartments we can control o In a closed compartment pressure and volume are inversely related Ex reducing the volume will increase the pressure Normal inspiration o Prior to normal inspiration atm and alveolar pressures are EQUAL o During inspiration Contraction of the diaphragm causes it to flatten increasing the volume of the thoracic cavity by increasing length Contractions of the external intercostals elevate the ribs and increase the volume of the thoracic cavity by increasing its width This causes the lungs and visceral pleura to be pulled outward and lung volume increases o INCREASED LUNG VOLUME DECREASED ALVEOLAR PRESSURE o When atm pressure exceeds alveolar pressure air moves into the lungs Normal expiration o This is a PASSIVE EVENT that involves no muscular contraction o 2 factors that decrease the thoracic cavity and lung volume Relaxation of inspiratory muscles Elastic recoil of lung o DECREASES IN LUNG VOLUME INCREASED ALVEOLAR PRESSURE o When alveolar pressure rises above atm pressure air moves out of the lungs The respiratory system is responsible for the movement of gases involved in Gas Exchange cellular metabolism Driving Force o Direction gas moves is dependent of the of that gas o A gas w in a compartment exerts a pressure which is proportional to the of that gas o More gas molecules exert great pressure o Gas molecules move down their pressure gradient Partial Pressure o In a mixture each individual gas exerts a pressure that is proportional to the of that gas within the mixture o this part of the total pressure is called PARTIAL PRESSURE o a gas moves along the part of the pressure gradient determine by its own Locations o gas molecules diffuse from regions of higher pressure higher to regions of lower pressure lower o At the LUNGS gas exchange occurs b w the alveolar and blood o At the SYSTEMIC TISSUE CELLS gas exchange occurs b w the blood compartments This is external respiration and systemic cell compartments This is internal respiration External Respiration o The gas exchange between the alveolar spaces in the lungs and the blood in pulmonary capillaries is called external respiration o Ventilation brings air rich is oxygen into the alveolar spaces in the o Air in the alveolar space has a lung has a High Po2 Low Pco2 o The blood in the pulmonary capillary compartment entering Lungs Low Po2 High Pco2 o Diffusion of gases is dependent on the partial pressure of the gases o O2 moves from the alveolar compartment to the capillary moves from the capillary compartment to the alveolar compartment o CO2 compartment Internal Respiration o The gas exchange between the systemic blood capillaries and tissue cells is called internal respiration o Blood high in oxygen and low in carbon dioxide circulates past tissue cells o The blood near the tissue has a High Po2 Low Pco2 o Each cell in the tissue compartment has a Low Po2 High Pco2 moves from the capillary blood compartment to the cell o O2 o CO2 moves from the cell compartment to the blood in the capillary compartment compartment Gas Transport Blood is medium used for gas transport O2 only available in lungs Because partial pressure of oxygen is higher in the alveoli than in the blood oxygen diffuses into the blood and is transported to systemic cells At the tissues the partial pressure is higher in the blood than in the cells so oxygen moves into cells where it promotes aerobic metabolism Cells generate CO2 during metabolic activity The blood transports the co2 to the lungs for removal Transport of Oxygen o Transported in 2 ways bound to hemoglobin in rbc as a dissolved gas in plasma o O2 is not very soluble in water so only small percentage is transported as a dissolved gas o Almost all o2 is transported bound to hemoglobin molecules o Hemoglobin molecules consist of 4polypeptide chains o Each chain contains iron containing heme group o An oxygen molecule binds to each iron in heme group o Hemoglobin that is not bound to o2 called deoxyhemoglobin Loading or association of oxygen to deoxyhemoglobin forms o Factors that affect hemoglobin s saturation with oxygen Greater of o2 molecules binding to hemoglobin increases saturation of hemoglobin When all of its oxygens binding sites are filled hemoglobin is considered to be saturated and is called oxyhemoglobin oxyhemoglobin o Association o Dissociation Occurs at the lungs Occurs at the tissue cells Factors Po2 pH PCO2 Temp BPG Hemoglobin type o Hemoglobin dissociation curve Thee partial pressure of oxygen is the primary factor influencing the degree of saturation of hemoglobin The po2 determines the of o2 molecules that can bind or dissociate from hemoglobin Blood in vessels coming from the lungs are high in Po2 so saturation is high Because o2 binds to all available sites Blood near skeletal muscle cells is very low in PO2 so saturation is low to the tissues O2 bound to oxyhemoglobin detaches and is unloaded o Blood pH values affect oxyhemoglobin saturation o Increased metabolic acids enhance dissociation of oxyhemoglobin and o For the same po2 the ability of hemoglobin to carry oxy in acidic the unloading of oxy blood is decreased BOHR effect cells o Low blood pH increases the unloading of 02 to actively metabolizing o Elevated blood pH increases the affinity of o2 to
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