New RS Flashcards
What are the main functions of the respiratory system ?
Gas exchange hormone production protection from pathogens regulation of body pH vocalisation
How do you calculate surface tension ?
0.5(pressure x radius of alveoli)
As a percentage of vital capcity what is the normal FEV of a healthy person ?
more than 70%`
What does it mean if perfusion limited ?
not enough blood to carry away oxygen
rapid transfer of oxygen from the alveolus to the capillaries
equilibrium reached before the end of the capillary bed
What are the factors that affect gas exchange in the lungs ?
surface area
thickness of the membrane
pressure gradient
solubility of gas
Why would HPV be taking place in birth ?
lungs are hypoxic until birth
How can COPD trigger HPV ?
COPD can cause a decrease in ventilation - leads to HPV - increases pulmonary pressure
What causes dissociation of oxgen from Hb ?
low partial pressure of oxgen reduces the affinity of Hb for o2- dissociation
In what conditions would 2.3 DPG be produced ?
exercise
anaemia
high altitudes
lung didease
What is the purpose of the chloride shift ?
maintain the membrane potential between erythrocyte and blood
How do central chemoreceptors measure changed in carbon dioxide production ?
Carbon dioxide diffuses from the cerebral capillaries into the CSF
reaction with water leads to proton and bicarbonate production
protons bind to the central chemoreceptors in the floor of the IVth ventricle
trigger an increase in VR
What effects does the autonomic system have on the lungs ?
mucus secretion
vasoconstriction
bronnchodilation
What is cheynes stokes respiration ?
partial pressure of oxygen and carbon dioxide never stabilises
due to delay in blood reaching the peripheral chemoreceptors
lungs alternate between deep fast breathing and shallow breathing
How does venous and arterial oxygen change during exercise ?
venous oxygen drops
arterial oxygen is stable
What does high altitude trigger ?
hypoxic ventilatory response
hyperventilation
How does hyperventilation alter pH ?
decrease in carbon dioxide
alkalosis
How is blood and CSF pH normalised after 3 days ?
bicarbonate transported out the of the CSF into the blood
central chemoreceptors reset
bicarbonate taken cre by the kidney
What are the functions of the lower respiratory tract ?
conduct air
gas exchange
regulate flow
What is the structure of alveolar cells type 1 ?
single cell thick
side facin the blood has holes- leaky
side facing the lung is strengthened with collagen fibres
How can bronchiole diameter be regulated ?
parasympathetic- Ach acts on M3 receptors- bronchoconstriction
Symapthetic- Noardrenaline- bronchodilation- Beta 2 receptors
What is poiuselles law ?
change in pressure/ r4
What affects airway resistance ?
viscosity
turbulent or lamina flow
Which structures have the highest resistance ?
bronchi
How are the first ribs joined to the manubrium ?
synchondroses
How do you work out pressure ?
2 X st/radius
What is the size of dead space ?
150 ml
What is the physiologic dead space ?
anatomic + alveolar dead space
How is diffusion capacity optimised ?
shape of type 1 alveolar cells
fusion of the alveoli with the basement membrane
Describe a perfusion limited scenario ?
not enough blood to carry away oxygen
rapid transfer of gas between alveoli and the blood
equilibrium reached before the end of the capillary bed
What are the perfusion limited gases ?
N20 and O2
What does the perfusion graph show ?
p cap on the side
palv on bottom
Describe a diffusion limited scenario ?
Slow transfer of gas between the alveoli
equilibrium not reached in transit time
What is a diffusion limited gas ?
CO
What happens in emphysema ?
alveoli are ruptured
reduced FEV
loss of elastin and connective tissue
What are the conditions at the apex ?
V>Q
High pH
Alveoli squeeze capillaries
What are the conditions at the base ?
Q>V
low hydrostatic pressure to overcome
low pH
How can you assess perfusion using Xe 133 ?
Inject into blood
pooly soluble so it leave via the lungs
poorly perfused- fainter - apex
What does a pulmonary embolus do ?
blocks perfusion
no gas transfer
fainter stain
What happens in HPV ?
Reduced oxygen in the alveolus and therefore gradient blood not fully oxygenated HPV blood diverted to well ventilated areas V/Q match
How is COPD linked to HPV ?
COPD means less oxygen in the blood
triggers HPV
increase in pulmonary pressure
leads to right ventriculr heart failure and pulmonary oedema
What does Hb also bind to ?
Protons
CO
NO
What does NO bind to ?
cysteine residues
vasodilator
How is co2 transported ?
70% in bicarnbonate buffer system
23% bound to N terminus
7% soluble
What is the bicarbonate buffer system ?
Carbon dioxide diffuses into capillaries
reacts to water to form carbonic acid and protons and bicarb
Excess bicarb which shifts equilibrium
so in the blood bicarb leaves the RBC and chloride replaces it
in the lung chloride leaves the RBC and Bicarb enters so the reaction can happen in reverse
Co2 released in the lungs
What is the bohr effect ?
protons reduces the affinity of Hb for O2
What is the haldane effect ?
Carbon dioxide reduces Hbs affinity for O2
What potentiates the O2 response ?
low O2 and high Co2/low pH
What do glomus cells signal through ?
IX
How is low oxygen detected by peripheral chemoreceptors ?
Low oxygen in blood K channels close cell depolarises Ca enters through Ca channels exocytosis of dopamine vesicles bind to dopamine receptors signal through IX
What does decreasing alveolar co2 do ?
potentiate the response
What is the BBB impermeable to ?
protons and bicarb
What is the effect of consciosuness on HR ?
during unconsciousness we tolerate more carbon dioxide
less sensitive
in a heroin overdose - less sensitive and autonomous activity is not stimulated enough
Where are the pulmonary stretch receptors located ?
airways
visceral pleura
What is the output of DRG ?
phrenic
What does the VRG contain ?
mixture of ins and exp neurones exp at the end
What is the pre botzinger complex ?
collection of insp neurones in the VRG
generate basic rhythm
What is forced expiration controlled by ?
pre botzinger complex
What is the voluntary control system ?
cerebral cortex
to the RC in medulla
output to the respiratory muscles
What is the involuntary system ?
limbic system- emotional response
hypothalamus- temperature regulation
What are the changes to ventilation during exercise ?
increase in TV
increase in VR
more capillaries
increased diffusion capacity
What are the stimulants of pulmonary ventilation in exercise ?
initially- neural - primary motor cortex
Increased K
muscle spindle and proprioceptors
What are eh consequences of hyperventilation ?
remove co2
alkalosis
increased affinity of Hb for O2
Reduced VR
How can pulomoanry oedema happen in hypoxic cinditions ?
HPV
increased pulmoanry pressure
high hydrostatic pressure
balance between hydrostatic and oncotic pressure diturbed
What are the long term adaptation to high altitude ?
bicarbonate transported out of the CSF reduced CSF pH resets the central chemoreceptors Bicarbonate taken care by the kidneys central more sensitive
What happens in sustained hypoxia ?
2,3 DPG made in the RBCs
curve shifts to the right- facilitate oxygen release
peritubular cells in the kidney detect low oxygen- release EPO - RBC synthesis increased- increased oxygen carrying capacity
heart has to pump more due to increased viscosity of the blood
How do gangrene and frostbite occur ?
vasoconstriction of peripheral arteries
in low temperatures
What is average arterial co2 pressure ?
40 mmHg
What do peripheral chemoreceptors sense ?
oxygen below 60 mmHg
