Respiration Flashcards
Static transmural pressures
Difference between alveolar pressure and inter pleural pressure
What does compliance of the lung depend on and how?
Volume- low vol- high compliance
How does fibrosis effect compliance?
Same change in pressure results in small change in vol
How does emphysema effect compliance?
Same change in pressure results in big change in vol
How do emphysema and fibrosis effect FRC?
Emphysema- increase Fibrosis- decrease
Components of elastic recoil in the lungs
Elastic nature of cells, ECM and surface tension
What does Laplace’s equation mean in the lungs?
pressure in the larger sacs is lower the smaller sacs so air will flow into larger sacs from small causing them to collapse
Under laminar flow the movement of air in and out of lungs is proportional to what?
The pressure gradient and inversely proportional to the resistance
Equation for movement of air
V= change in pressure / resistance
Under turbulent conditions the rate of gas movement is proportional to what?
The square root of the pressure difference
What is Reynolds number?
2rvp/ n
What are the units for airway resistance?
cmH20.s.litres
What happens in emphysema?
Loss of elastic tissue and break down of alveolar wall, tethering between walls adjoining airspaces is reduced, flimsy airways
What is flow rate going up dependant on?
Dependant on effort
What is flow rate going down dependant on?
Not Dependant on effort
What does COPD cause at a given volume?
Airway resistance is higher
What happens in the Gs pathway?
Gs activated, stimulates AC, cAMP, PKA, which acts on IP3 receptor decreasing its sensitivity to IP3 which reduces MLCK, it also phosphorylates MLCP which stimulates the phosphatase, As subunit stimulates potassium channels so hyperpolarise the cells membrane reducing calcium influx via Cav
What receptors act through the Gs pathway?
B2 adrenergic receptors, VIP receptors
What happens in the Gi pathway?
Activation of Gi receptors leads to inhibition of Adenylate cyclase- so counteracts the stimulatory effects of Gs, inhibits BK channel
What receptors act through the Gi pathway?
M2 muscarinic
What does histamine do to bronchial smooth muscle?
Constriction
What receptors does parasympathetic control work through?
M3 (contraction) and M2 to stop over contraction - on the presynaptic for negative feedback
What receptors does sympathetic control work through?
B2 adrenergic
What is the asthma response?
Movement of inflammatory cells into airways, release of inflammatory mediatory causing bronchoconstriction
What activity is asthma associated with?
Increase in parasympathetic activity on M2 receptor
Give examples of animal experiments showing M2 is effected in asthma?
Antigen challenge, virus, vitamin A deficient, ozone exposure
What is antigen challenge?
Change in M2 function linked to eosinophils, eosinophils clusters around nerve fibres and release major basic protein which inhibits M2
How do anticholinergics treat asthma?
Block effects of Aah- actions mainly via M1 and M3 receptors
Give an example of an anticholinergic.
Tiotropium bromide
How do glucocorticoids treat asthma?
Anti-inflammatory actions, activated GRE and reduces inflammatory genes and reduces mRNA instability
What nerve match the pre-botzinger complex output? how is this known?
Hypoglassal (12th cranial nerve). Brain slices taken and do electrophysiology
What are the 2 centres in the pons and what do they do?
Pneomotaxic- Inhibits respiratory to reduce rate
Apneustic - stimulates respiratory centres to increase rate and depth
How does the Hering- breur reflex happen?
Stretch receptor- vagus nerve-inhibitory centres-phrenic nerve-diaphragm
