L36: Mechanics Of Breathing Flashcards
What does a bigger radius do to collapsing pressure?
It decreases collapsing pressure
What is the law of Laplace equation?
P= 2T/r
P=Collapsing pressure on alveoli
T= surface tension
R= radius
What does decreased surfactant in the alveoli do?
It increasing collapsing pressure
What is it called when alveoli collapse?
Atelectasis
How does surfactant reduce collapsing pressure?
It disrupts intermolecular forces in the fluid lining the alveoli
When does surfactant synthesis being in a developing fetus?
24 weeks
When is surfactant always present in a developing fetus?
Week 35
Can collapsed alveoli participate in gas exchange?
No, they are not ventilated (but they are perfused)
What is the major site of airway resistance?
Medium sized bronchi (generations 5-10)
Is the PNS or SNS active in the airway at rest?
PNS cholinergic
What does PNS stimulation do to the airway?
Constriction of bronchial smooth muscle (decreased airway diameter and increased airflow resistance)
What does atropine do?
It blocks the effects of the PNS with muscarinic rejectors
When is the SNS dominant in respiration?
During exercise
What does activation of the SNS do to the respiratory system?
Results in relaxation of bronchial smooth muscle, increased airway diameter, and decreased airflow resistance via activation of B2 receptors
What happens to the airway in asthma?
- Resistance is increased
- thickening of walls from inflammation and histamine induced edema
- plugging of airway by secretion of mucous
- Airway hyperresponsiveness, constricting spasms
What do people with asthma have increased sensitivity to?
Smoke, cold air, and exercise
What are the treatment options for asthma and what do they do?
- B adrenal agonists : relax smooth muscle
- Corticosteroids: decreased inflammation
- Antileukotrienes: decrease inflammation
What happens in emphysema?
- Collapse of airways and destruction of alveolar walls
- Macrophages release trypsin, which overridden the protective alpha1-antitrypsin
The driving force of the diffusion of gases comes from***.
The partial pressure difference of the gas
What are the two things that the diffusion coefficient of a gas depends on?
Molecular weight and solubility
What is Henrys law, including the equation?
-Gases in solution are carried in dissolved form
Cx= Px x solubility
What has is only in the dissolved form and is never bound or modified?
Nitrogen
What is Dalton’s law of partial pressure and the equation?
-the partial pressure of a gas in a mixture of gases is the pressure that gas would exert if it occupied the total volume of the mixture.
Px = Pb x F
**if humidified :
Px = (Pb - PH2O) x F
What is the value of PH2O? Value of F?
PH2O= 47
F= 0.21
What equation would you use to determine the collapsing pressure of an alveoli?
Law of Laplace
