Respiratory Physiology

Question 1

External Respiration

Answer 1

• All processes involved ini exchanging O2 and CO2
• Pulmonary breathing
• Gas diffusion across membranes and capillaries
• Transport of O2 and CO2 between alveolr/tissue capillaries

Question 2

Internal Respiration

Answer 2

• Cellular respiration
• Involves the uptake of O2 and production of CO2 within individual cells

Question 3

Functional Residual Capacity

Answer 3

• Volume of air in lungs after passive expiration
• Opposing elastic recoil forces of lungs and chest are in equilibrium and no exertion by diaphragm or muscles

Question 4

Compliance

Answer 4

• Measure of how stretchy the lungs are
• Elastin collagen, surface tension of liquid in lung
• Low compliance, inc stiffness affects pressure needed to expand lung volume=more work

Question 5

Resistance

Answer 5

• Degree of ease in airflow
• Determined by airways number, length, diameter
• Deep inhalation reduces resistance

Question 6

Inhalation Muscles

Answer 6

• Diaphragm and External intercostals
• Inc size of thoracic cavity
• Decreases pleaural pressure
• Inc vol, dec pressure, allowing air to enter

Question 7

Exhalation

Answer 7

• Passive relaxation of external intercostal and diaphragm
• Forced, contraction of internal intercostals and abdominal muscles
• Dec size of thoracic cavity
• Inc pleural space
• Diaphragm gets smaller, dec size, inc pressure, air leaves

Question 8

Respiratory Centers (4)

Answer 8

• Pons
  
  • Pneumotaxic center
  • Apneustic center
• Medulla
  
  • Dorsal resp group
  • Ventral resp group

Question 9

Medullary Respiratory Center

Answer 9

• Main control center
• Dorsal resp group
  
  • Inspiratory neurons (reg inhalation)
  • Rhythmically firing, thus sets normal rhythym
• Ventral respiratory group
  
  • Contain inspiratory and expiratory neurons
  • Become active during periods when demands on ventilation are increased

Question 10

Pons Centers

Answer 10

• Pneumotaxic Center
  
  • Sends impulses to the dorsal neurons that help switch off inspiratory neurons
• Apneustic center
  
  • Prevents inspiratory neurons from being switched off, provide extra boost to inspiratory drive

Question 11

How are signals transmitted from the 4 respiratory centers to muscles

Answer 11

• Periodic firing of Dorsal Respiratory Group neurons sends impulses via phrenic nerve to diaphragm

Question 12

Minute Alveolar Ventilation

Answer 12

• Volume of FRESH air introduced into the gas exchanging regions of the lungs per minute
• Min Alveolar ventilation=Rate (Vt tidal volume - Vd dead space)
• Then multiple by how many times you breathe in a minute
• Alveoli contain less O2 and more CO2 than atmospheric air

Question 13

Distribution of Alveoli Size

Answer 13

• Bc of gravity alveoli at base are smaller, alveoli at apex are larger
• Bc of surfactant small alveoli open easier than large alveoli
• Base receives majority of ventilation
  
  • Amount of air per unit time brought into the lungs
• Remeber the slinky

Question 14

Partial Pressure of O2 and CO2 in atmosphere

Answer 14

• Atmosphere Composition
  
  • 79% Nitrogen
  • 21% Oxygen
  • 0.03% CO2
  • P= 760mm Hg
• PO2= 0.21 x 760=160
• PCO2= 0.0003 x 760= 0.23

Question 15

Partial Pressure of O2 and CO2 in atmosphere vs alveoli

Answer 15

They are not the same due to high CO2 contributin from the venous blood

Alveolar PO2 is 104 (vs 160 atm)

Alveolar PCO2 40 (vs 0.23)

Question 16

Oxygen Delivery to RBC Percentages

Answer 16

• 1.5% suspended in plasma
• 98.5% will be bound by hemoglobin

Question 17

CO2 Pick up

Answer 17

• CO2 diffuses into blood stream
  
  • 7% remains dissolved in plasma as CO2
  • 93% Diffuses into RBC
    
    • 23% binds to hemoglobin forming Hb-CO2
    • 70% Converted to H2CO3 (carbonic acid) by carbonic anhydrase
      
      • This will immediately dissociate into H= and bicarbonate
      • H+ removed by buffers, hemoglobin
      • Bicarbonate moves out of RBC in exchange for chloride
      • All of these rxns are reversed to deliver CO2 to lungs