PHYSIOL [D] Flashcards
define respiration
process of burning of glucose for energy (cellular level)
define “breathing”:
process of getting gas in and out of your lungs
via what process do cells and tissues(cells) get nutrients?
diffusion
what is “Fick’s” law?
that gas moves from high -> low concentration
what does Fick’s law depend on?
- gradient (ΔC)
- permeability of membrane (P)
- area (A)
- molecular weight (MW)
- distance (D)
what is the equation for Fick’s law?
ΔC x P x A
net rate of diffusion = —————-
MW x D
problem with multi-cellular organism & nutrient diffusion?
cells in the middle(further away) too far from air, just diffusion process alone not sufficient
…solution? transfer system!
how long does it take for one RBS to go through your circulation?
1 minute
how many branches are there in the conducting airways?
28
within conducting pathways where does exchange actually occur?
end of branches in the alveolus
no exchange occurs along pathways - this is “dead” space
what part of the respiratory tract are reinforced with cartilage?
trachea
bronchi
what are the non-respiratory functions of the respiratory system?
- enhances venous return(cardiac suction pump)
- contributes to normal acid-base balance(CO2)
- enables vocalisations
- defends against inhaled foreign matter
- excretes some drugs(ethanol, anaestetics)
- route for water and heat eliminations
partial pressure:
in a mix of gases each component behaves separately
how do you calculate the partial pressure of one component of gas?
conc.(%) of that gas x total pressure
eg. AIR! oxygen = 21% nitrogen = 79%
total pressure @ sea level = 760mmHg
partial pressure of O2 = 0.21 x 760 = 150mmHg
how would the % composition change at everest?
% stays the same!
partial pressure is what changes
how to calculate transmural pressure across lung wall?
intra-alveolar pressure - intra-pleural pressure
how to calculate transmural pressure across thoracic wall?
atmospheric pressure - intra-pleural pressure
what is the intra-alveolar pressure @ rest?
760mmHg same as atmospheric!
what is the intra-pleural pressure?
slightly lower! 756mmHg
what nerve innervates the diaphragm?
phrenic nerve
what nerve innervates the external intercostal muscles?
intercostal nerve
what is enlargement of thoracic cavity during quiet respiration due to?
75% enlargement is due to contraction and flattening of the diaphragm
describe effects of thoracic expansion on pressures in lung:
decreases intra-pleural pressure (down to 754)
- > lungs drawn into area of low pressure
- > increase volume
- > decrease in intra-alveolar pressure
- > below atmospheric pressure => air enters lungs due to pressure differences
contraction of external intercostal muscles?
“bucket handle” elevation of ribs
=> increases side to side dimension of thoracic cavity