Physio of Breathing

  1. Is inhalation an active process?
  2. Is exhalation an active process?
  3. Is phrenic nerve activity associated with inhalation or exhalation?
    Inhalation; phrenic stimulates the diaphragm to contract
  4. What happens to the activity of the phrenic nerve during exhalation?
    Stops stimulating the diaphragm
  5. What happens to the diaphragm when the phrenic stops firing?
    Diaphragm relaxes
  6. Is breathing automatic or autonomic, and what does that mean?
    • Automatic, because diaphragm is a skeletal muscle, it is not under autonomic control
    • Additionally, phrenic nerve is a somatic motoneuron
  7. Is phrenic nerve a somatic motoneuron or autonomic neuron?
    Somatic motoneuron
  8. Where does the phrenic exit?
    Spinal cord
  9. Where do the cell bodies of the phrenic nerve located?
    C3-C5 of the spinal cord
  10. Where does the axon of phrenic nerve terminate?
  11. True/False: diaphragm is a smooth muscle
    False, it is a skeletal muscle
  12. What is the phrenic nerve neural activity during exhalation?
    No activity/ action potentials fired
  13. Describe the phrenic nerve neural activity during inhalation:
    Starts off with low in early inhalation, followed by moderate in middle inhalation and then high activity in late inhalation
  14. True/False: Phrenic nerve fire rate oscillates with respiratory cycle
  15. True/False: phrenic nerve firing frequency during inhalation is fast and furious
    False, it is slow and steady
  16. True/false: there is a sharp decline in the phrenic nerve firing rate graph during exhalation
  17. Why is the phrenic nerve firing rate slow and steady?
    Stimulate a slow and sustained diaphragm contraction, which leads to a slow and steady filling of lungs with air
  18. What is the lung volume at the end of inspiration?
    Volume plateaus because no more air flow
  19. What is the air flow at the end of inhalation?
  20. What would happen if the phrenic nerve simply fired at maximum rate during inhalation?
    Forceful and abrupt gasps
  21. What does the phrenic nerve firing rate over time graph look like when there is not slow and steady phrenic nerve firing?
    No ramp
  22. What is the most important regulator of the respiratory rhythm, aka- regulate the firing rate of phrenic nerve?
    Dorsal respiratory group (DRG)
  23. Where is the DRG located?
    Dorsal portion of the medulla within nucleus of solitary tract (NTS)
  24. What is the function of DRG?
    Receives input to regulate breathing by controlling phrenic nerve’s firing rate
  25. What type of neurons are found in the DRG?
    Interneurons and pre-motor neurons
  26. What does DRG stand for?
    Dorsal respiratory group
  27. Where does the DRG receives its sensory input from?
    • Vagus nerve
    • Glossopharyngeal nerve
  28. True/False: DRG determines firing rate of the phrenic nerve during both inspiration and expiration
    False; there is no phrenic activity in expiration, so inspiration ONLY
  29. Which type of breathing, eupnea or hyperpnea, do DRG mainly play a role in?
  30. During eupnea, which structure contributes to the firing rate of phrenic nerve?
    Dorsal respiratory group (DRG)
  31. True/False: DRG neurons have an intrinsic firing rate
  32. Does DRG cause phrenic to ramp up or down during inhalation?
    Ramp up, phrenic fires when DRG fires
  33. DRG firing stops during which phase of respiration?
  34. Where is the ventral respiratory group (VRG) located?
  35. What neurons make up the VRG?
    Interneurons and premotor neurons
  36. What does VRG stand for?
    Ventral respiratory group
  37. True/False: VRG contributes to both inspiration AND expiration
    True. Unlike DRG, VRG DOES contribute to both phases of respiration
  38. When does VRG get activated?
    When there is an increased demand for breathing – hyperpnea
  39. Which structure is more active during hyperpnea?
    Ventral respiratory group
  40. What are the medullary structures that control breathing?
    • DRG
    • VRG
  41. Where is pneumotaxic center located?
    Dorsal region of the pons
  42. What is the function of pneumotaxic center?
    • Stops the inhalation ramp – inhibiting DRG
    • Inhibit apneustic center
  43. Where do the neurons in the pneumotaxic center innervate?
    inhibitory neurons to DRG
  44. how does the pneumotaxic center affect breathing when it is firing a lot? A little?
    • Decreases time spent in inhalation, lungs filled only partially when firing a lot
    • Increases time spent in inhalation and lungs fill with excess air when fires a little
  45. Does tidal volume go up or down with pneumotaxic center firing a lot? A little?
    • Goes down
    • Goes up
  46. Is respiratory cycle longer or shorter when pneumotaxic center fires a lot? A little?
    • Shorter
    • longer
  47. What happens to respiratory rate when pneumotaxic center fires a lot? A little?
    • Respiratory rate increases, because respiratory cycle shortens
    • Respiratory decreases, because respiratory cycle lengthens
  48. What is the apneustic center and what inhibits it?
    Apneustic center exerts excitatory influence on DRG, pneumotaxic center inhibits it so inspiratory drive decreases as a result and DRG stops the phrenic ramp
  49. How does the pneumotaxic center stop the phrenic nerve ramp?
    • Direct inhibition of DRG
    • Indirect inhibition of dorsal respiratory group via the apneustic center
  50. Where is the apneustic center located?
    Lower pons
  51. What is the function of apneustic center?
    Excited the DRG, and increase inspiratory drive
  52. What happens with over stimulation of the apneustic center?
    Prolonged inhalations and brief exhalations
  53. Damage to what region of the nervous system likely results in apneustic breathing?
    Central nervous system i.e. head trauma or stroke
  54. Describe what apneustic breathing is?
    • Prolonged inhalations and brief exhalations
    • Inspiratory pauses
  55. What are the pontine structure that control breathing?
    • Pneumotaxic center (upper pons)
    • Apneustic center (lower pons)
  56. Does the cerebral cortex directly innervates DRG?
  57. Is cerebral cortex under voluntary or involuntary control of breathing?
  58. Which structure does the cerebral cortex projects to control the diaphragm?
    Phrenic nerve
  59. What are the blood gas consequences for hyperventilation?
    • More oxygen enters blood as a result of increase partial pressure O2 in alveoli
    • More CO2 leaves the blood as PCO2 alveoli go down
  60. What are the blood gas consequences for hypoventilation?
    • Less oxygen enters blood
    • Less carbon dioxide leaves blood
  61. Where are central chemoreceptors located?
    Ventral surface of medulla
  62. Where do central chemoreceptors synapse on?
  63. Where are peripheral chemoreceptors located?
    Carotid and aortic bodies
  64. Which is most sensitive to H+, central or peripheral chemoreceptors?
    Central chemoreceptors
  65. Which is most sensitive to Oxygen, central or peripheral chemoreceptors?
    Peripheral chemoreceptors
  66. True/False: carbon dioxide can also activate central chemoreceptors along with H+
  67. True/False: carbon dioxide and H+ can also activate peripheral chemoreceptors along with oxygen
  68. Does activation of the peripheral and central chemoreceptors increase or decrease respiratory rate and minute ventilation (Ve)?
  69. Which of these can cross the blood-brain barrier: H+, CO2?
  70. High or low pH and high or low CO2 would increase the discharge frequency of central receptors?
    • Low pH (High [H+])
    • High carbon dioxide
  71. True/False: Increased rate of breathing is associated with decreased pH and increased CO2
  72. True/False: central chemoreceptors are also stimulated by oxygen
    False, central chemoreceptors do not respond to O2, only peripheral
  73. Peripheral chemoreceptors are always exposed to arterial or venous blood?
  74. Peripheral chemoreceptors mainly sense O2 or CO2 levels of arterial blood?
    Arterial oxygen levels mainly, some arterial CO2 and H+ concentration
  75. What levels of O2, CO2 and pH would increase the discharge of frequency of peripheral chemoreceptors?
    • Low arterial O2
    • High CO2
    • Low pH (high H+)
  76. True/false: decreased blood pH would lead to increased rate of breathing
  77. True/False: carotid body firing rate decreases when arterial PO2 drops from 100 mmHg to 60 mmHg
    False; carotid body firing (a peripheral chemoreceptor) would increase firing rate when there is a drop in arterial O2 pressure – think: low O2, you need more O2 so breathe more
  78. Which is the most important signaling molecule during hypoxia?
  79. Describe the hypoxia intracellular response:
    • Hypoxia closes K+ channel in carotid bodies
    • K+ channel closing leads to DEPOLARIZTATION of those cells, thereby opening Ca2+ VG channels, letting calcium in
    • Ca2+ promotes release of NT: ATP, Ach, dopamine
  80. Which structures/ receptors directly carry signal to DRG?
    • Apneustic center
    • Peripheral chemoreceptors
    • Central chemoreceptors
    • Lung stretch receptors
    • Muscle and joint receptor
  81. What structure(s) directly inhibit DRG?
    Pneumostaxic center
  82. What type of receptors are lung stretch receptors?
  83. Where are lung stretch receptors located?
    Bronchi and bronchioles
  84. How are lung stretch receptors activated?
    When lungs become overstretched
  85. What happens when lung stretch receptors are activated?
    Stimulate vagus which then carries the signal to the DRG to switch OFF the inspiratory ramp
  86. What is the purpose of the lung stretch receptors?
    Prevent lungs from getting overstretched by switching off the inspiratory ramp of DRG
  87. What is the name of the reflex that switches off the inspiratory ramp after lung stretch receptor is activated?
    Hering-Breuer reflex
  88. What type of receptors are muscle and joint receptors? Where are they found?
    • Mechanoreceptors
    • Found in skeletal muscles and joints
  89. When are muscle and joint receptors activated?
    During exercise
  90. What happens when muscle and joint recpeotrs are activated?
    Synapse on DRG that leads to increase in respiratory rate and depth
Card Set
Physio of Breathing
Pulmonary Midterm