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IPHY 3430 9-15-11

IPHY 3430 9-15-11. RESPIRATORY SYSTEM Purpose: Maintain blood levels of O2 and CO2 as homeostatic variables. Fig. 13-2, p. 453. Additional parts of anatomy involved in respiration Nervous system: Pons, Medulla Phrenic nerve and other motor nerves.

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IPHY 3430 9-15-11

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  1. IPHY 3430 9-15-11

  2. RESPIRATORY SYSTEMPurpose:Maintain blood levels of O2 and CO2 as homeostatic variables

  3. Fig. 13-2, p. 453

  4. Additional parts of anatomy involved in respirationNervous system: Pons, MedullaPhrenic nerve and other motor nerves

  5. Physical Principles1. Gas flows from area of high pressure to low pressure2. The rate of flow depends on the pressure gradient: the greater the gradient, the faster the flow and the larger the volume of air that moves3. When gas is compressed in a smaller volume, the pressure increases.

  6. INHALATION1. Medulla sends signal via motor nerves to diaphragm and external intercostals, causing contraction2. Those muscles cause expansion of the volume of the thoracic cavity3. The increased volume of the thoracic cavity causes the lungs to expand4. The expansion of the lungs causes a decrease in air pressure in the lungs relative to outside air5. Air flows into lungs down pressure gradient until air pressure equalized.

  7. During inhalation/exhalation at rest:pressure differential of about 1 mm 760 759 mmHg 761 760 Exhalation at rest Inhalation at rest

  8. EXHALATION AT REST1. Air flow in during inhalation stops when pressure equalized2. Stimulus from medulla ceases, causes muscles to relax.3. Elastic properties of the muscles and rib cage cause decrease in volume of thoracic cavity, which causes a decrease in lung volume4. Decrease in volume of lungs causes increase in air pressure in lungs relative to outside5. Air rushes out of lungs until pressure equalized.

  9. During inhalation/exhalation at rest:pressure differential of about 1 mm 760 759 mmHg 761 760 Exhalation at rest Inhalation at rest

  10. VARIATION IN RESPIRATORY EXCHANGE DURING EXERCISE1. In exercise, increased muscle contraction leads to greater expansion of thoracic cavity and decrease in air pressure in lungs2. Decreased air pressure in exercise leads to greater air inhalation and exhalation3. Increased number of breaths/min

  11. During exercise, pressure differentials greater than 1 mm generated due to greater numbers of muscles contracting with greater force, resulting in larger expansion of thoracic cavity and lungs. Inhalation Exhalation 760 750 770 760 mmHg

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