BIOL 112 1st Edition Lecture 19 Outline of Last Lecture I Shift at Birth II Pathologies Defects III Blood Outline of Current Lecture IV Measurement of Blood Volume V Gas Exchange VI Respiratory System VII Breathing Ventilation Current Lecture I Measurement of Blood Volume Too crude to cut a major vessel to drain all the blood and measure it obviously General approach dilution method Inject measured amount of labeled substance into blood allow substance to mix in blood and withdraw a sample and measure the extent to which the substance has been diluted These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Plasma Volume Use a soluble dye dye must be inert and cannot pass through cell membranes Evans Blue is usually used Hematocrit the proportion of volume of whole blood occupied by cells mostly erythrocytes usually around 40 If hematocrit is 40 of volume then plasma occupies 60 of volume II Gas Exchange Aerobic cells need Oxygen and release Carbon Dioxide which are exchanged with the environment source of gasses atmosphere Barometer invented by Evangelista Torricelli 1643 measures atmospheric pressure the weight of air pressing down on mercury Hg pushes it up the tube to fill the vacuum Gas pressure can be expressed as the height of Hg in a column Not necessary to use mercury the earlier barometer by Torricelli used water but water is less dense Partial Pressure 1 atmosphere pressure 760 mm Hg Can parse the contributions of each gas to the total air pressure partial pressure It is a more biologically significant expression of available gas concentration for gas exchange Humans at High Altitude Humans at 15 000 ft or higher show mental and physical impairment within an hour or less from hypoxia Solutions to problem Breathe pure oxygen the upper limit is 40 000 ft Above that limit even pure oxygen can t support life Pressurize cabin Comparative Gas Exchange Cells need to be 1 mm from environment for adequate gas exchange Sample organisms protozoa primitive metazoa Bigger organisms especially lang organisms need specialized exchange structures Fish and other aquatic organisms gills Insects tracheae and spiracles Terrestrial organisms lungs III Respiratory System Structures of the Respiratory System Nasal passages Pharynx with epiglottis Larynx with vocal cords Trachea Bronchi Bronchioles Alveoli Ribs Intercostal Muscles Diaphragm Functions of Respiratory System Breathing obviously lungs and stuff Air Processing preparing the air for use by alveoli Vocalization Gas Exchange IV Breathing Ventilation In mammals air is pulled into lungs Inhale diaphragm contracts pulls down and intercostal muscle contraction lifts rib cage Both actions increase volume of chest cavity creating a partial vacuum Air rushes into lungs to relieve vacuum Exhale In Simple Exhalation relaxed muscles diaphragm returns to arch shape intercostals allow rib cage to rotate down gently pushes air out of lungs In Forcible Exhalation accomplished by contraction of a different set of intercostal muscles forces rib cage down abdominal muscles contract force organs upward diaphragm up reduce volume of chest cavity and force air out of lungs Alveolar Ventilation Tidal volume 500 ml Not all lung volume is alveoli in bronchi and bronchioles there is no gas exchange Dead volume 150 ml lungs are never completely empty So alveolar volume 500 150 350 ml with each tidal breath Alveolar Ventilation respiratory rate X alveolar volume 12 min X 350 ml 4 200 ml min moved in and out of alveoli 21 of this is oxygen so 880 ml oxygen in lungs min Human at rest consumes 200 ml 02 in lungs min Extra supply of oxygen becomes available for activities without in creasing volume or rate of breathing