anim_regulation_ventilation _answer_key.doc

Regulation of Ventilation To complete this worksheet, select: Module: Gas Exchange and pH Balance Activity: Animations Title: Regulation of Ventilation Introduction 1. a. Describe normal ventilation as a continuous cycle of inspiration and expiration. Normal ventilation is rhythmic and involves continuous cycles of inspiration and expiration. b. What regulates this continuous cycle? There are various regions of the brain – medulla oblongata and pons – that regulate the rhythmic pattern of ventilation. Basic Rhythm 2. Explain the role of the inspiratory and expiratory areas of the brain. These are located in the medulla oblongata. During normal quiet ventilation only the inspiratory area is active, but during forced ventilation both are active. 3. What is a spirogram? – This is a recording of airflow within the respiratory system. 4. a. Describe inspiration stimulation by the inspiratory area of the brain. During normal breathing, nerve impulses are spontaneously generated from the inspiratory area to the medulla. These impulses stimulate the respiratory muscles (diaphragm and intercostals). Inspiratory muscles contract and air moves into the lungs. b. Describe passive expiration. The inspiratory muscles relax after about 3-4 seconds and passive elastic recoil occurs. Air is forced out of the lungs as the intercostal and diaphragmatic muscles recoil and relax. 5. Explain the role of accessory inspiratory muscles and how they are stimulated during forced inspiration. The accessory muscles allow inspiration to be more forceful. The stimulation of the accessory muscles is accomplished by way of the inspiratory area. 6. Explain stimulation and the role of the expiratory area during forced expiration. The inspiratory area activates the expiratory area which sends impulses to the expiratory muscles – internal intercostals and abdominal muscles – these contract resulting in a forced exhalation. Control of Ventilation Rate by Other Brain Centers 7. Describe how each of the following parts of the pons modifies ventilation rate. Pneumotaxic area Inhibits the medullary rhythmicity area, shortens inspiration and results in rapid breathing. Apneustic area Stimulates the inspiratory areas, prolongs inspiration resulting in slower, deeper breathing. 8. Describe how the hypothalamus contributes to ventilation regulation. The hypothalamus responds to emotions, pain, and temperature. These centers, when activated, stimulate the respiratory centers in the pons and medulla to alter the ventilation rate. 9. a. Describe how the cerebral cortex supplies a limited level of respiratory control. Cerebral cortex impulses bypass respiratory centers in the medulla and pons and allows for conscious breathing. b. Why is cortical control essential? It allows the individual to regulate and control consciously the ventilation breathing rhythm. Effects of Blood Chemistry 9. What is function of chemoreceptors in the central and peripheral nervous systems. To monitor the level of oxygen, carbon dioxide and hydrogen ion concentrations in the blood. 10. a. Describe the respiratory response to increasing CO2 and H+ as detected by chemoreceptors. When carbon dioxide and hydrogen levels rise, or oxygen levels drop, impulses from the chemoreceptors stimulate the inspiratory areas in the medulla. This excitation increases respiratory rate b. Define hyperventilation This is a greater intensity of the rate and depth of breathing. c. How do these adjustments contribute to homeostasis? Increasing the rate a depth of breathing removes more carbon dioxide, increases blood pH and increases oxygen inflow returning values to normal. 11. a. Describe the respiratory response to decreasing CO2 and H+ as detected by chemoreceptors. When carbon dioxide or hydrogen ion levels decrease and oxygen levels increase impulses from the chemoreceptors inhibit the inspiratory areas. This inhibition decreases respiratory rate and brings about hypoventilation. b. Define hypoventilation. Hypoventilation is a decrease in the intensity of rate and depth of breathing. c. How do these adjustments contribute to homeostasis? Hypoventilation allows carbon dioxide to accumulate, allows for a decrease in pH and also allows for a decreased oxygen inflow promoting a return to normal values.