Topic 8: Respiratory System Flashcards
Describe the mechanism of elastic recoil in the respiratory process including what causes it
Elastic forces from the alveoli cause a ‘rebound’ effect of the lungs forcing air out after having been stretched by inhalation
These forces are due to collagen and elastin
Compliance = Change in Vol / Change in Pressure
What is compliance?
The ability of the lungs to stretch / expand in response to pressure.
High compliance: Lungs easily stretch + expand but decreased recoil ability
Low compliance: Stiff lungs, makes it difficult to take air in
Another mechanism employed by the lungs in alveolar surface tension. Explain this phenomenon.
The pressure that this exerts on the air inside the lungs can be calculated via Laplace’s Law:
P = 2 x T // radius
The higher the P value the lower the pressure (as wider radius means more stretched alveoli and higher pressure).
The surface tension of fluid molecules on the inside of the alveoli exerts a pressure on the air inside
Rate of Gas Transfer (g) proportional to A/T x D x (P1 - P2)
What do the symbols mean
A = area
T = Thickness of permeable membrane
D = Diffusion constant
Ps = Partial pressure
Surfactants are composed of a)_________ (90%) and b)________ (10%). They are produced by c)____________ and their function is to d)___________ surface tension by e)__________ liquid molecules on the inner membrane of alveoli
Surfactants are required to keep the alveoli spacious and well-inflated
- alveolar type II cells
- decrease
- interrupting
- lipids
- proteins
a) lipids
b) proteins
c) alveolar type II cells
d) decrease
e) interrupting
What is Dalton’s Law (hint = sum pressures of gasses)
the total pressure of a mixture of gasses in a mixture = the sum of all the pressures of individual gasses
What is Henry’s Law in relation to the concentration of gas in a liquid?
At constant temp, the number of molecules dissolving in the liquid is directly proportional to partial pressure of the gas
Haemoglobin consists of 4 subunits (2 alpha chains, 2 beta chains). Each haem group can bind one oxygen molecule. How many oxygen molecules can a haemoglobin molecule bind? and what is the oxygen capacity of haemoglobin (per g haem)
4
1.39ml / g Hb
Match the factors below to the result you would see on the O2 - Hb dissociation curve:
a) Increase in:
- CO2
- [H+] (decrease pH)
- 2, 3-diphosphoglycerate
- temp
b) Decrease in:
- same as above
- Shift left
- Shift right
a) Shift right
b) Shift left
hint = CADET face Right!
What are the effects of:
a) CO on O2 transport
b) Anaemia on O2 transport
c) Being a foetus on O2 transport
a) CO binds 40% of O2 binding sites
b) Less haem to bind o2
c) Foetal Hb has higher affinity for o2
What are the 3 ways CO2 is transported in the blood (and their rough %)?
- 8-10% in solution
- 60-87% as bicarbonate
- 5-30% bound by haemoglobin
What is the Haldane effect in relation to to CO2 transport
Carrying capacity for CO2 is greater for deoxygenated blood
Hypoventilation can be caused by 3 things
- Decreased lung compliance
- Increased resistance (mucus accumulation)
- CNS depression
What does adequate perfusion of alveoli look likein relation to:
a) Tidal volume a) Frequency
b) Anatomic Dead Space b) Total ventilation
c) Alveolar Gas c) Alveolar ventilation
d) Capillary blood d) Pulmonary blood flow
a) 500ml a) 15/min
b) 150ml b) 7500ml/min
c) 3000ml c) 5250ml / min
d) 70ml d) 5000ml / min
Regulation of Ventilation
In the brain stem, the a)___________ (PRG / Pons) neurons integrate sensory information and interact with medullary neurons to influence ventilation via the action of the b)__________ (VRG) and c)__________ (DRG) in medulla that control respiratory muscles.
The VRG and DRG receive both d)________ and e)________ input from chemo-sensors
a) Pontine Respiratory Group
b) Ventral Respiratory Group
c) Dorsal Respiratory Group
d & e) Peripheral / Central
