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The Respiratory System



Mechanics of breathing | Gas Exchange | Oxygen in the Blood | CO2 Gas Exchange | Nervous Control of Respiration | Chemical control of Respiration | 

The Mechanics of Breathing | Top
Much like any machine we will explain breathing as well coordinated machine. We've broken down the mechanics of breathing into the following notes for easier reading.
  • First: The Diaphragm contracts and moves down.
  • The lungs expand (normal breathing requires little intercostal involvement)
  • This creates a vacuum-and allows oxygen to rush in.
  • The diaphragm contracts forcing oxygen out of the lungs
  • The respiratory system takes advantage of the natural process-diffusion(sometimes facillitated diffusion)
  • Serfacant is used for short periods of time, to allow for gas exchange
    ---About a collapsed Lung---
  • The most important part of a lung is Elasticity! (Hence Elastic fibers are the dominant extracellular material
  • If there is a tear/damage to the lung, the lungs integrity is damaged (a similar situation happens when fluid is in your lungs)

    Gas Exchange | Top
  • Gas exchange occurs between the blood and air.-and takes place in the alveolies.
  • air and other empty passages are called dead air space.
  • Alveolies-number about 300 million, with the surface of a tennis court!!
  • Repiratory membranes-If fluid increased, this would decrease the amt. of gas exchange.If surface area decreased, this would decrease the amt. of surface area
  • Partial pressure-If liquid contains less oxygen than air, Oxygen will move into the liquid till air and liquid contain the SAME volume.
  • This is what happens when you inhale, oxygen moves into alveolar capillaries which contain little oxygen and abundant carbon dioxide


    • Oxygen in the blood | Top
  • 97% of oxygen combines with Hema, in hemoglobin, to form oxyhemoglobin-this is from alveolar capillaries
  • Oxygen is low in the tissues, and high in blood
  • Factors incluencing the release of oxygen from oxyhemaglobin are, pH levels, excersize and temperature and cellular homeostasis.

    Carbon Gas Exchange | Top
  • 86% of carbon dioxide is diffused in plasma
  • It is then transported by blood proteins
  • 72% of CO2 is transported by bicarbonates (produced in pancreas)
  • Carbon dioxide and Water form Carbonic Acid (the enzyme Carbonic Anyhydrase controls the Rate)
  • during exhaliation carbon dioxide is taken from liquid to gas and exhaled OUT of hte body
  • Carbon dioxide comes from cells
  • Carbonic Acid does not stay in this structure but disassociates (into H30 & HC03)
  • The measure of pH comes from the number of hydronium ions (the more you have hte lower the pH) Blood pH homeostasis is 7.2-7.3

    Nervous Control of Respiration  | Top
  • The medula oblingata and lower pons make up respiration centers
  • Phrenic nerves, carry action potentials from diaphragm to respiratory centers and back
  • Action potentials fatigue quickly in respiratory centers. (Question: Why would you want this to happen?)
  • If fatigue of normal respiration takes place, the pons will take over rythmic breathing (but the pons is not efficient)
  • The hering-Breuer reflex-This structure senses respiration and sends messages to the medula oblingata-inhalation then stops, there is a brief pause and exhilation takes place.
  • Very important in infants and adults during Excersize!!
  • This is also related to SIDS because it causes rythmic breathing and malfunction.
  • Skin receptors located throughout your skin, also can stimulate respiratory centers and cna help reuglate breathing.

    Chemical control of respiration  | Top
  • chemo receptors in the medula oblingata attract small changes in carbon dioxide and oxygen and adjust breathing accordingly. (This could also be a suspect in SIDS)
  • Fainting can be a result of exagerated breathing
  • When carbon dioxide levels become low, blood levels in periphery begin to dialate
  • This causes blood to pull in abdomen and legs