Respiratory System 2

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crzhazen
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73484
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Respiratory System 2
Updated:
2011-03-17 10:36:43
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Respiratory System
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Respiratory System
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  1. Respiratory Muscles for Inspiration
    • Diaphragm: Prime driver of respiration
    • Contraction enlarges thoracic cavity and pulls air into lungs
    • Relaxation causes diaphragm to bulge upwards, compresses lungs, and expels air
    • Internal and External Intercostal Muscles: synergists to diaphragm, prevent rib cage from caving in during inhalation
  2. Accessory Muscles for Inspiration
    • Other chest and abdomen muscles also contribute to forced inspiration
    • They further increase chest diameter to create pressure gradient
  3. Quiet Expiration
    • Passive process
    • Muscles relax and elasticity of the bronchial tree causes recoil
    • Pressure is now higher inside bronchial tree, so air flows out
  4. Forced Expiration
    • Rectus abdominus and internal intercostals reduce chest diameter to force air out faster
    • Muscles in abdomen and pelvis raise pressure in the abdomen cavity and push organs up against the diaphragm, further increasing thoracic pressure
  5. Pressure and Airflow
    Airflow is proportional to the pressure difference
  6. Boyle's Law
    • More volume = less pressure
    • When thoracic cavity expands, pressure of air in lungs is reduced
    • If pressure in lungs is lower than atmospheric pressure, air riushes into lungs
    • The greater the difference, the more air enters in
  7. Resistance and Airflow
    • Airflow reduced as resistance increases
    • Small diameter bronchioles: more resistance
    • Sympathetic nervous system causes bronchodilation
    • Parasympathetic nervous system, cold air, chemical irritants cause bronchoconstriction
    • Decreased pulmonary compliance = more resistance
    • Lungs can't expand as easily (usually disease)
  8. Neural Control of Breathing
    • No pacemaker cells in lungs
    • Breathing require repetitive firing of motor neurons to respiratory muscles
    • Neurons is pons and medulla integrate information for unconscious breathing
    • Can be modified by motor cortex for voluntary breathing
    • Phrenic nerve supplies diaphragm, intercostal nerves supply intercostal muscles
  9. Ventral Respiratory Group
    • Contain inspiratory and expiratory neurons
    • Inspiratory neurons fire for about 2 seconds, causing motor neurons in spinal cord to initiate diaphragm/intercostal contractions
    • Also inhibit expiratory neurons
    • When the inspiratory neurons stop firing, the expiratory neurons fire for about 3 seconds and allow relaxation of muscles
  10. Dorsal Respiratory Group
    Integrates information from pons, chemoreceptors, stretch receptors, irritant receptors to modify ventral respiratory group output
  11. Pontine Respiratory Group
    Integrates information from hypothalamus, limbic system, cerebral cortex to modify ventral respiratory group output during sleep, exercise, vocalization, emotional responses
  12. Central Chemoreceptors
    Monitor pH of CSF in medulla
  13. Peripheral Chemoreceptors
    • Monitor pH (and O2, CO2 concentrations) of blood in aortic arch and carotid artery
    • Low pH indicates high CO2 levels, which increase respiratory rate
  14. Stretch Receptors
    • Activated with extreme dilation of bronchi and bronchioles
    • Inhibit inspiratory neurons in ventral respiratory group
  15. Irritant Receptors
    • Activated when smoke, dust, pollen, or any other irritant contacts epithelial cells of airway
    • Causes shallower breathing, bronchoconstriction, breath-holding, coughing
  16. Voluntary Control of Breathing
    • Voluntary breathing initiated my motor cortex
    • Signals travel down cerebrospinal tract, synapse directly onto motor neurons of respiratory muscles in spinal cord
    • Voluntary control has its limits, eventually autonomic control takes over
  17. Alveolar Ventilation
    • Not all air that enters respiratory system reaches alveoli for gas exchange
    • Anatomical dead space: conducting division of respiratory system
    • Physiological dead space: Anatomical dead space + pathological damage that prevents gas exchange
    • Typically if 500 ml of air is inhaled, 150 remains in dead space
    • Alveoli never completely empty
    • Residual volume: 1300 ml
  18. Measurement of Lung Capacity
    Spirometers measure rate/depth of breathing, speed of expiration, rate of oxygen consumption
  19. Tidal volume
    Amount of air inhaled/exhaled in one cycle
  20. Inspiratory Reserve Volume
    Amount of excess air that can be inhaled
  21. Expiratory Reserve Volume
    Amount of excess air that can exhaled
  22. Residual Volume
    Amount of air remaining in lungs after maximum expiration
  23. Vital Capacity
    • Total amount that can be inhaled/exhaled with maximum effort
    • (TV+IRV+ERV)
    • Best measure of pulmonary health
  24. Inspiratory capacity
    • Maximum amount that can be inhaled after normal tidal expiration
    • (TV+IRV)
  25. Functional Residual Capacity
    • Amount of air remaining after normal tidal expiration
    • (RV+ERV)
  26. Total Lung Capacity
    • Total amount of air the lungs can hold
    • (RV+VC)
  27. Eupnea
    At rest, normally 12-115 breaths per minute
  28. Apnea
    A few skipped breaths
  29. Dyspnea
    Shortness of breath
  30. Hyperpnea
    Increased breathing rate
  31. Hyperventilation
    Extreme increase in breathing rate
  32. Hypoventilation
    Decreased ventilation rate
  33. Gas Exchange
    Gas will dissolve in blood depending on its partial pressure
  34. Ventilation-Perfusion Coupling
    Blood flow and ventilation must match to be most efficient
  35. Gas Exchange in Tissues
    • Oxygen bound to hemoglobin in RBC is unloaded
    • CO2 diffuses mostly into RBC, some binds to hemoglobin, most converted to bicarbonate and H+ (lower pH)
  36. Gas Exchange in Alveoli
    • CO2 diffuses into alveoli
    • Bicarbonate converted back to CO2
    • Oxygen binds to hemoglobin
  37. Oxygen-Hemoglobin Binding
    • Each hemoglobin molecule can bind four oxygen molecules
    • The more oxygen available, the more it binds to hemoglobin
  38. Temperature Affects Hemoglobin Saturation
    Tissues that are active and need oxygen are warmer, which facilitates oxygen unloading
  39. pH Affects Hemoglobin Saturation
    Active tissues produce a lot of CO2, which lowers pH and facilitates oxygen unloading
  40. Bisphsphoglycerate (BPG)
    • Also promotes oxygen unloading (shifts curve to right)
    • Elevated body temperature, thyroxine, growth hormone, testosterone, epinephrine induce production of BPG
    • BPG also produced when you go to higher altitudes
  41. Acidosis
    • Blood pH lower than 7.35
    • Usually caused by hypercapnia (excess CO2 levels)
    • Hyperventilation is then initiated to exhale CO2 faster than it is produced
  42. Alkalosis
    • Blood pH higher than 7.45
    • Usually caused by hypocapnia
    • Hypoventilation is initiated to allow CO2 to build up
  43. Hypoxia
    Inability to get oxygen to tissues or for tissues to use oxygen
  44. Hypoxemic Hypoxia
    Respiratory problems
  45. Ischemic or Anemic Hypoxia
    Circulatory problems
  46. Histotoxic Hypoxia
    Tissue problems

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