physiology supplementary Flashcards
boyle’s law
pressure is inversely proportional to volume
how are lungs linked to thorax (2 ways)
intrapleual fluid cohesiveness negative intrapleural pressure (lungs push out and thorax pushes in )
what is alveolar surface tension
attraction between water molecules at liquid air surface, resist lung stretching
laplaces law
P = (2T) / r
what does laplaces law mean
smaller alveoli have a greater tendency to collapse
how are smaller alveolis prevented from collapse
surfactant reduces surface tension
alveoli interdependence
if one alveoli collapses the others save it
what is the normal inspiratory capacity
females - 3500ml males - 4500 ml
what is FRC
volume of air in lungs at the end of a normal passive expiration. ERV+RV
what is IC
the max volume of air that can be inspired at the end of a normal quiet expiration
TV + IRV
when does residual volume inc
when the elastic recoil of the lungs is lost eg emphysema
can total lung volume be measured by spirometry?
no because RV cant be measured by spirometry
what does dec pulmonary compliance cause
SOB on exertion
what is dec pulmonary compliance seen in
restrictive diseases
why is alveolar ventilation less than pulmonary ventilation
because of anatomical dead space
define pulmonary ventilation
vol of air breathed in and out per minute
define alveolar ventilation
vol of air exchanged between the atmosphere and the alveoli per minute
what is physiological dead space
anatomical + alveolar dead space
what is alveolar dead space
ventilated alveoli that are not adequately perfused with blood
daltons law
total pressure exerted by a gaseous mixture is the sum of the partial pressures of each individual component in the gas mixture
compare the diffusion coefficient of CO2 to O2
CO2 is 20x more than O2
ficks law
The amount of gas that moves across a sheet of tissue in unit time is proportional to the area of the sheet but inversely proportional to its thickness
henrys law
The amount of a given gas dissolve in a given type and volume of liquid (e.g. blood) at a constant temperature is: proportional to the partial pressure of the gas in equilibrium with the liquid
how is most O2 found in the body
bound to Hb
what is the primary factor that determines the percent saturation of Hb with O2
PO2
how does anaemia effect O2 conc of bood
dec Hb concentration and dec O2 conc of blood
describe the oxygen Hb binding curve
sigmoidal
what is the taut form of Hb
deoxyHb
what is the relaxed form of Hb
oxyHb
what is the Bohr effect
The Bohr Effect Facilitates the Removal of O2 from Haemoglobin at Tissue Level by Shifting the O2-Hb Dissociation Curve to the Right
foetal Hb subunits
2 alpha and 2 gamma
compare foetal Hb affinity or Hb
higher than normal - curve is shifted left
when if foetal Hb replaced by adult Hb
a few months after birth
where is myoglobin present
skeletal and cardiac muscle
ratio of haem molecule to myoglobin binding
1:1
what does the presence of myoglobin in the blood indicate
muscle damage
what does myoglobin provide
a short term storage for O2 in anaerobic conditions
describe the myoglobin curve and what it means
hyperbolic - myoglobin releases O2 at a very low PO2
how is the majority of CO2 transported
as bicarbonate
what helps the formation of bicarbonate from CO2 and H2O and where does this occur
carbonic anhydrase, occurs in RBC
describe the haldane effect
removing oxygen from Hb inc the ability of Hb to pick up CO and H ions
what is the point of the Bohr and haldane effect
O2 liberation and uptake of CO and H ions at tissues
what generates the breathing rhythm
pre botzinger complex
how does normal inspiration come about
firing of the dorsal respiratory group neurones
how does passive expiration come about
the dorsal neurones cease firing
how does active expiration come about
ventral neurones fire - excite the internal intercostals and abdominals etc
where can the breathing rhythm be modified
pons - pneumotaxic centre
what does the PC do
inhibit inspiration
wha would happen without PC
apneusis
when is the PC stimulated
when the dorsal neurones fire (inspiration)
what does the apneustic centre do
prolong inspiration
describe general breathing rhythm control
generated in the medulla and modified in the pons
which receptors guard against hyperinflation
pulmonary stretch receptors - Hering Breuer reflex
what are the juxtapulmonary receptors stimulated by
pulmonary congestion and oedema (LVF), also pulmonary emboli
cause rapid shallow breathing
what TV will the pulmonary stretch receptors be activated at
>1 l
which receptors contribute to the inc ventilation during exercise
joint
what do chemoreceptors sense
the value of gas tensions
what do peripheral chemoreceptors sense
oxygen and CO2 and H conc in blood
what do central chemoreceptors respond to
H conc of CSF
how is CSF separated from the blood
blood brain barrier
what can cross the BBB
CO2 NOT H and HCO3
when is the hypoxic drive important
at high altitudes and with COPD
when is the hypoxic drive stimulated
PO2 <8kPa
what is hypoxia at high altitudes stimulated by
dec partial pressure of insired oxygen
what is the acute reponse to hypoxia at high altitudes
hyperventilation and inc CO
what are the symptoms of acute mountain sickness
headache, fatigue, nausea, TACHYCARDIA, dizziness, sleep disturbance, exhaustion, shortness of breath, unconsciousness
what does the chronic adaption to hypoxia involve
inc RBC production, inc 23 DPG production, inc number of capillaries, inc no of mitochondria and kidneys conserve acid and METABOLIC ACIDOSIS
what is inc RBC production called
polycythaemia
how do the peripheral chemoreceptors adjust for acidosis
sense H ions and cause hyperventilation and inc elimination of CO2 from the body
what is diabetic ketoacidosis
Hyperventilation with a severe metabolic acidosis.
