Pulmonary Ventilation- The respiratory system is responsible for the movement of gasses involved incellular metabolism- 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 Moves gases in and out of the lungso 2.Gas Exchange 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 Blood gases are transported to the lungs (pulmonary circ.) Blood gases are transported to the organs and tissues throughout the body (systemic circulation.- Ventilation-phaseso The process of bringing air into and out of the lungs: Inspiration: air moves into the lungs Expiration: air moves out of the lungso Proper ventilation is important to promote airflow, which enhances gas exchange.- Ventilation- driving forceso Direction of airflow is determined by changing pressureso Air flows from high to low pressureo Pressure can be altered by changing the volume - Pressure volume relationshipo Changing the relative pressure in the compartments we can control the direction of airflow.o In a closed compartment, pressure and volume are inversely related. Ex: reducing the volume will increase the pressure.- Normal inspirationo Prior to normal inspiration, atm and alveolar pressures are EQUALo During inspiration Contraction of the diaphragm causes it to flatten, increasing thevolume 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 PRESSUREo When atm pressure exceeds alveolar pressure, air moves into the lungs.- Normal expirationo 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 lungo DECREASES IN LUNG VOLUME= INCREASED ALVEOLAR PRESSUREo When alveolar pressure rises above atm pressure, air moves out of the lungs.Gas Exchange- The respiratory system is responsible for the movement of gases involved in cellular metabolism- Driving Force o Direction gas moves is dependent of the [] of that gaso A gas w/in a compartment exerts a pressure, which is proportional to the [] of that gaso More gas molecules exert great pressureo Gas molecules move down their pressure gradient- Partial Pressure o In a mixture, each individual gas exerts a pressure that is proportionalto the [] of that gas within the mixtureo 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 []o gas molecules diffuse from regions of higher pressure (higher []) to regions of lower pressure (lower [])- Locations o At the LUNGS, gas exchange occurs b/w the alveolar and blood compartments. This is external respirationo At the SYSTEMIC TISSUE CELLS, gas exchange occurs b/w the blood 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 respirationo Ventilation brings air, rich is oxygen, into the alveolar spaces in the lungo Air in the alveolar space has a: High Po2 Low Pco2o The blood in the pulmonary capillary compartment (entering Lungs) has a: Low Po2 High Pco2o Diffusion of gases is dependent on the partial pressure of the gaseso O2 moves from the alveolar compartment to the capillary compartment.o CO2 moves from the capillary compartment to the alveolar compartment.- Internal Respiration o The gas exchange between the systemic blood capillaries and tissue cells is called internal respirationo Blood, high in oxygen and low in carbon dioxide, circulates past tissue cells.o The blood near the tissue has a: High Po2 Low Pco2o Each cell in the tissue compartment has a: Low Po2 High Pco2o O2 moves from the capillary blood compartment to the cell compartment.o CO2 moves from the cell compartment to the blood in the capillary 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 plasmao 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 moleculeso Hemoglobin molecules consist of 4polypeptide chainso Each chain contains iron containing heme groupo An oxygen molecule binds to each iron in heme groupo Hemoglobin that is not bound to o2 called deoxyhemoglobin Loading or association of oxygen to deoxyhemoglobin forms oxyhemoglobino Association Occurs at the lungso Dissociation Occurs at the tissue cellso 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 Factors:- Po2- pH- PCO2- Temp- BPG- Hemoglobin typeo 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- O2 bound to oxyhemoglobin detaches and is unloaded to the tissueso Blood pH values affect oxyhemoglobin saturationo Increased metabolic acids enhance dissociation of oxyhemoglobin andthe unloading of
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