Human Organ Systems Test 2, Respiratory System

Main factor is to keep PaCO2 (arterial partial pressure of CO2) around 40mmHg

• Resistance and compliance affect the bellows
• Efferents cause diaphragm to contract and lower pleural pressure, causing lungs to be "sucked" open and pressure to fall in alveoli
• Exhalation occurs when the muscle relax and alveolar pressure is raised because the lungs want to be smaller. Depends on elastic recoil of lungs and how narrow/collapsible the airways are
• Total lung capacity is a good measure of the lung muscle function

• The pressure difference needed to drive flow

Typically is 5 H2O/L/s

• The ease of which the volume of something can be changed
• Alveoli at the bottom of teh lung
• Typically is around 70 to 100 mL/cm H2O

• The lung is less compliant during inflation than deflation
• This helps us have alveoli available for recruitment

Caused by decreased elastic recoil causing increased compliance of the airways. This results in the lungs being overinflated and alveolar pressure being high at the end of respiration (whereas in us, it equals atm pressure). Elevated pressure at the end of expiration is called intrinsic Positive-End Expiratory Pressure (PEEP) and it must be lowered in order to drive inspiratory flow

• Partial pressure gradients drive diffusion
• Hg carries O2
• Chloride shift/bicarbonate ion carries CO2

Pulmonary arterioles constrict in a low P_AO2 environment (decreased perfusion to the area of decreased ventilation)

• Facilitate aerobic metabolism
• Control [H+] via excretion of CO2
• Heat exchange
• Immune surveillance
• Inactivation/activation of circulating substances

The faster a fluid or gas moves, the lower its pressure

It wants to be big! Except for when we have more than ~70% of our total lung capacity; then the chest also wants to be small along with the lungs

• aka stiffness
• The inverse of compliance (change in P over change in V)

• The pressure between the lungs and the chest wall
• This pressure is about 5cmH2O lower than Patm on average
• The pleural pressure varies on location in the lung due to gravity

• Occurs in large airways
• Reynolds number determines how probable turbulent flow is
• It is 'bad' because it requires greater driving pressures than laminar flow because the air molecules must be forced to go in the same direction

P_A - P_P