Respiratory Physiology Lab using Vernier computer-assisted recording equipmentpg 1Respiratory Physiology LabControl of Respiratory CycleThe respiratory cycle of inspiration and expiration is controlled by complex mechanisms involving neurons in the cerebral cortex, brain stem, and peripheral nervous system, as well as central and peripheral receptors. These receptors respond to a variety of stimuli including chemicals and pressure. Central respiratory control (respiratory drive) occurs in the pons and medulla, which respond directly to chemical influences. Other input is received from stretch receptors in the lungs and chemoreceptors located in the carotid and aortic bodies (see Figure 1). Respiratory chemoreceptors respond most sensitively and rapidly to carbon dioxide but also to oxygen and pH (acidity). Constant adjustments in the respiratory cycle occur throughout the day to allow gas exchange in the lungs to maintain a steady level of CO2 in the bloodstream. An increase in the CO2 level stimulates breathing, while a decrease inhibits it. If the deviation from the “set point” is large enough you may experience shortness of breath. The oxygen level can also influence the respiratory cycle, but larger deviations are required before its influence is felt. CO2 and its Effect on Blood pHAt rest, the average adult male producesapproximately 200 mL of CO2 each minute, butthis may increase to over 2000 mL with exerciseor heavy work. Carbon dioxide is carried in theplasma of the bloodstream as bicarbonate (HCO3-)and hydrogen ions (H+). Upon entering the blood,especially during internal respiration, CO2 andwater move into erythrocytes where they areconverted by erythrocyte carbonic anhydrase intocarbonic acid (H2CO3) and subsequentlybicarbonate and hydrogen ions according to thereversible reaction: CO2 + H2O <--> H2CO3 <--> HCO3- + H+.Increased blood CO2 concentration(hypercapnea), such as when this gas enters thebloodstream in the tissues, decreases the pH of theblood (acidosis) because CO2 is rapidly convertedinto hydrogen ions. Decreased blood CO2concentration (hypocapnea) which occurs in lungcapillaries, shifts the equilibrium equation to theleft, reducing H+ concentrations and raising bloodpH (alkalosis). The ventilation of the lungs, specifically respiratory rate and depth, is the strongest effector of blood CO2 and blood pH. Hyperventilation lowers CO2 levels (causing hypocapnea) due to an increased opportunity for gas exchange in the lungs. Hyperventilation is defined as faster and/or deeper breathing than normal. Holding one’s breath or re-breathing air (such as breathing into a paper Figure 1Respiratory Physiology Lab using Vernier computer-assisted recording equipment pg 2Computer 20bag) raises CO2 levels (hypercapnea) because there is less opportunity for gas exchange.In this experiment, you will alter CO2 levels by holding your breath (hypoventilation), rapid breathing (hyperventilation), and exercise. You will compare the respiratory rate, tidal volume, and minute ventilation that result from each physiologic challenge to homeostasis. Important: Do not attempt this experiment if you are currently suffering from a respiratory ailment such as the cold or flu. OBJECTIVESIn this experiment, you will- Obtain graphical representation of normal tidal volume.- Compare tidal volumes generated by various physiologic challenges.- Correlate your findings with real-life situations.MATERIALScomputerVernier computer interface disposable bacterial filterLogger Pro nose clipVernier SpirometerPROCEDUREPart I Tidal Volume Response to Breath Holding1. Start computer and plug in Vernier Labpro into outlet. Connect the Spirometer into CH1 (on the front left side) on the labpro using the white square plug. Use the USB cable to connect the labpro to the computer (The small, square connector plugs into the USB port on the right side of the labpro. The wide connector end plugs into the USB port on the left side of the laptop.) Launch the Logger Pro software using the icon on the quick launch toolbar on the bottom of the laptop screen. From the ‘File’ menu, ‘Open’ the file “20 Respiratory Response” from the Human Physiology with Vernier folder.2. Attach the larger diameter side of a bacterial filter to the “Inlet” side of the Spirometer.3. Hold the Spirometer in one or both hands. Brace your arm(s)against a solid surface, such as a table, and click tozero the sensor. Note: The Spirometer must be held straightup and down (as in Figure 2) during data collection. 4. Collect inhalation and exhalation data.a. Put on the nose clip.b. Click to begin data collection. c. Taking normal breaths, begin data collection with aninhalation and continue to breathe in and out. After 4cycles of normal inspirations and expirations fill yourlungs as deeply as possible (maximum inspiration) andhold your breath for 40 s.d. After 40 s of breath holding, resume normal breathing. Data will be collected for 120 s.Respiratory Physiology Lab using Vernier computer-assisted recording equipment pg 35. Click the Next Page button, , on the toolbar to seethe volume data. If the baseline on your volumegraph has drifted, use the Baseline Adjustmentfeature to bring the baseline volumes closer to zero,as in Figure 3. Select a representative peak andvalley in the portion of your graph prior to the onsetof breath holding. Place the cursor on the peak andclick and drag down to the valley that follows it.Enter the -y value displayed in the lower left cornerof the graph to the nearest 0.1 L as the BeforeChallenge Tidal Volume in Table 1. 6. Select two adjacent peaks in the portion of yourgraph prior to the onset of breath holding. Click anddrag the cursor from one peak to the next. Use the -x value displayed in the lower left corner of the graph to calculate the respiratory rate in breaths/minute. Enter this value to the nearest 0.1 breaths/min as the Before Challenge Respiratory Rate in Table 1.7. Repeat Steps 6 and 7, selecting regions in the portion of your graph after normal breathing had been resumed (between 60–80 s). Enter the values in the After Challenge section in Table 1.8. Calculate the Minute Ventilation values for before and after the challenge and enter the results to the nearest 0.1 L in Table 1. (Tidal Volume)(Respiration Rate) = Minute VentilationPart II Tidal Volume Response to Rapid Breathing1. Clear the data from Part I by choosing Clear All Data from the Data