cardio 3.1 Flashcards
where can we find intra-alveolar pressure (intrapulmonary)
In the lungs
through what two forces is negative intrapleural pressure established
1) The lungs natural tendancy to recoil
2) The surface tension of the alveolar fluid (surfactant) constantly cacts to draw the alveoli to their smallest possible demension
what opposes the lung collapsing forces
The natural elasticity of the chest wall, pulls the thorax outward, and and enlarges the lungs.
what allows the negative pressure of the lungs and the elastissticity of the chest wall to coexist
the strong adhesive force between the parietal and visceral pleura (think water between two pieces of glass)
what pressures are involved in breathing (4)
- atmospheric pressure
- intra-alveolar pressure
- intrapleural pressure
- transpulmonary pressure
what pressures keeps the lungs from collapsing
the difference between the intrapulmonary and intrapleural pressures (Ppul - Pip)
what determins the size of the lungs at any given time
thanspulmonary pressure (greater the pressure, the larger the lungs)
what is Boyle’s law
P1V1 = P2V2
what is alveolar pressure equal to at rest
atmospheric pressure (alveolar pressure = 0)
what is the intrapleural pressure at rest
Negative, the opposing forces of the lungs are trying to collapse and the chest wall trying to expand a negative pressure in the intrapleural space
what is the Lung volume at rest
FRC (think waves)
when inspiratory muscles contract, what occurs to the thorax
volume increases
what happens to the alveolar tissue pressure as the lung volume increases
decreases to less then atmospheric pressure
as the pressure in the lungs becomes negative, what occurs
airflow will continue until the pressure radiant dissipates
what happens to the interpleural pressure during inspiration
it becomes more negative
what occurs as the lung volume increases concerning recoil and the interpleral space
the elastic recoil strength increases- as a result the interpleural space becomes even more negative
how much will the lung volume increase by in a normal inspiration
One TV
during expiration, what occurs to the the alveolar pressure
becomes greater than atmospheric pressure (due to increases elastic forces on the lungs)
what happens to the interpleural pressure when
1) Normal expiration
2) forced expiration
1) intrapleural pressure returns to normal
2) intrapleural pressure becomes positive
how does positive pressure effect expiration
makes it more difficult
energy obtained during expiration help over come what 3 factors
- airway resistance
- alveolar surface tension
- lung compliance
how does contraction and relaxation of bronchial smooth muschle effect airway resistance
it alters the radius of the airways
what effect does parasympathetic stmilation have on the airways
constricts the airway (muscurinic agonist, irritants and the slow reacting substances on anaphylaxis)
sympathetic stimuilation and sympathetic agonist do what
- dilate the airway via beta2 receptors
- increase the radius
- decrease the resistances to airflow
