Respiratory system Flashcards
external respiration:
pulmonary ventilation + pulmonary diffusion
internal respiration:
transport to and from tissue + capillary diffusion and exchange
pleural membrane:
makes the lungs ‘stick’ to the inside of the rib cage - the lungs are inflated and compressed with each breath (ventilatory cycle)
fluid filled space between lungs and ribs prevents the lungs collapsing
inspiration / inhalation:
active process:
- external intercostal muscles contract to raise the rib cage and move it outwards - increases thorax volume
- diaphragm contracts to becomes flatter - increases thorax volume
- Boyle’s law: if volume increases, pressure must decrease = pressure in chest cavity falls below atmospheric pressure
- air flows into the lungs down pressure gradient
pressure change during inhalation:
at rest: 2-3mmHg
during heavy exercise: 80-100 mmHg
expiration / exhalation:
passive process:
- diaphragm and intercostal muscles relax and ribs fall
- volume of the chest cavity decreases
- Boyle’s law: pressure in lungs increases above atmospheric pressure
- air flows out of lungs down a pressure gradient
forced exhalation - during exercise:
active process: quicker than natural expiration
- contraction of the intercostal muscles cause the rib cage to move down and inwards
- volume of the chest cavity decreases
- increased pressure in lungs - air flows out of lungs
- diaphragm muscles relax and contraction of the abdominal wall raises the diaphragm
tidal volume =
volume moving in and out of lungs during each breath
vital capacity =
the greatest amount of air that can be expired after maximal inspiration
residual volume =
amount of air remaining in lungs after maximal expiration
total lung capacity =
sum of vital capacity and residual volume
average = 4-6L of air
bronchoconstriction can be caused by…
cold, allergens, parasympathetic activity
bronchodilation can be caused by…
sympathetic activity, exercise, beta2-adrenoceptor agonists (salbutamol)
Dalton’s law =
total pressure of a mixture of gases equals the sum of the partial pressure og the individu gases in that mixture
partial pressure =
contribution of individual gas to the total pressure
gaseous exchange at the alveoli:
gases move down their pressure gradient
PO2 in pulmonary arterial blood is lower than in the alveoli = O2 diffuses into blood
opposite for CO2
volume of gas transferred =
proportional to the (area over the thickness), multiplied by the (diffusion constant) and multiplied by the (difference in partial pressure)
transport of O2 in the blood:
2% dissolved in the blood
98% combined with haemoglobin (oxyhaemoglobin)
oxyhaemoglobin saturation curve:
oxygen loading at vessels near lungs - saturation stays high due to high O2 conc.
oxygen unloads at tissue - saturation changes quickly with even small changes in PO2
as PO2 increases, haemoglobin collects more O2 = higher saturation
transport of CO2 in the blood:
7-10% dissolved in plasma
10-20% combined with haemoglobin (carbaminohaemoglobin)
70-80% dissolved in blood as bicarbonate ions (hydrogencarbonate ions)
CO2 in blood as bicarbonate ions:
CO2 + H2O -> H2CO3 -> H+ + HCO3-
CO2 in plasma diffuses into rbc - combines with H20 to form carbonic acid catalysed by carbonic anhyrdase - this dissociates to form hydrogen ions and hydrogencarbonate ions - hydorgencarbonate ions diffuse into plasma (charge is maintained by chloride shift)
O2 within the muscles saturation curve:
steep saturation curve for myoglobin means that there is a very efficient delivery of O2 to the mitochondria
myoglobin has a higher affinity for O2 than haemoglobin - haemogloin passes O2 to myoglobin in the muscle
regulation of pulmonary ventilation:
mostly neuronal control but can also be voluntary control (e.g. holding breath)
respiratory control centres located in medulla oblongata and pons
regulation of inspiration:
stimulus = chemoreceptors detect changes in PO2, PCO2 and pH + signals from active muscles stimulate the inspiratory centre
response = external intercostal muscles contract to increase thoracic volume
regulation of expiration:
stimulus = the stretching of the lungs triggers the expiratory centre
response = intercostal and abdominal muscles relax or contract to decrease thoracic volume
pulmonary ventilation increases on exercise to match changing O2 demand:
- the initial change in ventilation rate is due to neural sympathetic drive
- later changes occur due to changes in chemical composition of the blood gases/pH = breath more
- ventialtion response may also increse in anticipation of exercise (try to control breathing) = overcompensation
- as soon as respiratory rate increases lactate forms
overcompensation leads to…
hyperventilation (breathing too much)
ventilatory equivalent for oxygen:
volume of air expired divided by volume of O2 consumed
varies little over a range of exercise = ventilation and O2 demand are well matched
respiratory quotient (RQ values)/ respiratoy exchange ratio (RER):
RQ = VCO2 (eliminated)/VO2 (consumed)
values of oxidation:
- carbohydrate = 1.0
- fat = 0.7
- protein = inbetween (0.8/0.9)
ventilatory threshold:
ventilation increases disproportionately to O2 consumption = ventilatory threshold
initially believed to be due to increase in blood lactate stimulating ventilation centres in brain
now believed to be due to needing to remove excess O2
could be due to overcompensation of breathing during exercise
respiratory limitations to performance:
as rate and depth of ventilation increases so does energy consumption of the muscles involved
use of energy for breathing doesn’t slow down exercise - respiratory muscles have high aerobic capacity
respiratory disorders that may limit the ability to exercise:
asthma
fibrosis
chronic obstructive pulmonary disease
asthma =
constriction of airways due to allergens or exercise
fibrosis =
lungs have fibrous tissue laid down - stiffer lungs, less elastic = difficulty breathing
vascular disorders that may limit the ability to exercise:
pulmonary hypertension
clots/thrombosis = ischemia
arterial occlusion
pulmonary hypertension =
high blood pressure in arteries in lungs
poor gaseous exchange
thickenning of pulmoanry arteris = become less compliant so cannot stretch as easily during systole
- reduce blood flow
- more work for right side of heart = heart failure
arterial occlusion =
caused by atherosclerosis - reduced blood flow to a limb (ischemia) = reduced metabolites/O2
can cause claudication (ischemic muscle pain) during exercise amd is relieved after rest
can result in gangrene if ischemia is prolonged = amputation of limb is needed
ischemia =
inadequate blood supply to a part of the body
