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Ventilation quiz #1

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  • How does Boyle's law explain the process of inspiration and expiration during ventilation?
    Boyle's law states that a change in volume leads to a change in pressure. During inspiration, the diaphragm contracts, increasing thoracic volume and decreasing intrapulmonary pressure, causing air to flow into the lungs. During expiration, the diaphragm relaxes, decreasing thoracic volume and increasing intrapulmonary pressure, forcing air out of the lungs.
  • What are the typical values and roles of atmospheric, intrapulmonary, and intrapleural pressures during a normal breathing cycle?
    Atmospheric pressure remains constant at 760 mmHg. Intrapulmonary pressure fluctuates: it drops to about -2 mmHg during inspiration (allowing air in), rises to +2 mmHg during expiration (forcing air out), and equalizes to 0 mmHg between breaths. Intrapleural pressure is always negative, typically -4 mmHg at rest, becomes more negative (about -6 mmHg) during inspiration, and returns to -4 mmHg during expiration, helping keep the lungs inflated.
  • What does Boyle's law state in relation to pressure and volume?
    Boyle's law states that a change in volume leads to a change in pressure; specifically, as volume increases, pressure decreases, and vice versa.
  • How does the diaphragm contribute to inspiration during ventilation?
    During inspiration, the diaphragm contracts and moves downward, increasing thoracic cavity volume and decreasing intrapulmonary pressure, which draws air into the lungs.
  • What happens to intrapulmonary pressure during expiration and why?
    During expiration, the diaphragm relaxes, decreasing thoracic volume and increasing intrapulmonary pressure, which forces air out of the lungs.
  • What is the typical value of atmospheric pressure at sea level, and does it change during ventilation?
    Atmospheric pressure is typically 760 mmHg at sea level and remains constant during ventilation.
  • How does intrapulmonary pressure change during a normal breathing cycle?
    Intrapulmonary pressure drops to about -2 mmHg during inspiration, rises to +2 mmHg during expiration, and equalizes to 0 mmHg between breaths.
  • Why is intrapleural pressure always negative, and what are its typical values during the breathing cycle?
    Intrapleural pressure is always negative due to lung recoil pulling on the pleural cavity; it is typically -4 mmHg at rest, becomes more negative (about -6 mmHg) during inspiration, and returns to -4 mmHg during expiration.
  • What causes air to flow into the lungs during inspiration?
    Air flows into the lungs during inspiration because the intrapulmonary pressure drops below atmospheric pressure, creating a pressure gradient that drives air inward.
  • What happens to the pressures in the lungs and pleural cavity immediately after expiration but before the next inspiration?
    Immediately after expiration, intrapulmonary pressure equalizes to atmospheric pressure (0 mmHg relative), and intrapleural pressure is at -4 mmHg.
  • Which muscle pair plays a key role in respiration during quiet breathing?
    The diaphragm and the external intercostal muscles are the primary muscle pair involved in respiration during quiet (restful) breathing.
  • What is the main muscle responsible for ventilation in the respiratory system?
    The diaphragm is the main muscle responsible for ventilation in the respiratory system.
  • What constitutes a complete respiratory cycle?
    A respiratory cycle consists of one inspiration (inhalation) followed by one expiration (exhalation).
  • How does positive pressure ventilation affect cardiac output?
    Positive pressure ventilation increases intrathoracic pressure, which can reduce venous return to the heart and thereby decrease cardiac output.