Respiratory System 2 Flashcards
what is daltons law of partial pressures?
- air we breathe made of n2, o2, h2o, co2
- there = diff % of each gas in air
- each gas makes up diff proportion of total mixture
- sum of pp = total pressure of air
- pp of various gases = imp in establishing gradients which drives gases through system
how is the pCO2 in peripheral tissues higher than in arteries returning from lungs?
CO2 = end product of cellular respiration
how is the pO2 lower in tissues than in arterial blood?
O2 continuously used by cells
what are the gradients of o2 and co2?
o2 - from blood to tissues
co2 - from tissue to blood
following internal respiration, what happens to o2 and co2?
o2 unloads to tissues
co2 uptake into blood
po2 in venous blood dec to 40 mmHg
pco2 in venous blood inc to 45mmHg
following ventilation, what happens to o2, co2?
po2 in alveoli inc
pco2 dec
what are the pressure gradients of o2 and co2?
o2 - lungs to blood
co2 - blood - lungs
what is a Hb mol composed of?
4 globin chains surrounding central haem group
2 alpha + 2 beta chains
4 o2 per Hb
saturated haemoglobin
when all 4 haems of mol bound to oxygen
partially saturated haemoglobin
when 1 to 3 haems bound to oxygen
the rate that haemoglobin binds + releases oxygen is regulated by …
- po2
- temp of blood
- pco2
- conc of BPG (2,3-bisphosphoglycerate)
in haemoglobin saturation, what happens if oxygen levels drop?
- more oxygen dissociates from haemoglobin + is used by cells
- resp rate / cardiac output don’t inc
co2 is transported in the blood in 3 forms
what are these?
- dissolved in plasma
- chemically bound to proteins
- bicarbonate ions in plasma
describe internal respiration at tissues using (formula)?
- co2 diffuses into RBC
- high conc of co2 equation to shift to right
- combines with water to = carbonic acid
- h2co3 dissociated into h+ + hco3-
- hydrogen ions attach to one of 4 haem mol knocking off one o2
- o2 travels down conc gradient to tissues
what is the chloride shift?
counterbalances the out rush of neg bicarbonate ions from RBCs
cl- ions move from plasma into erythrocytes
describe external respiration using (formula)?
- reaction shifts to left
- bicarbonate ions move into RBC + bind with h+ to make carbonic acid
- carbonic acid split into co2 + h20
- co2 levels rise
- co2 diffuses from blood into alveoli along conc gradient
what other factors can influence haemoglobin saturation?
- inc in temp, h+, pco2, BPG —> inc o2 uploading from haemoglobin
curve SHIFTS RIGHT
dec in these will shift curve left
dorsal respiratory group / inspiratory centre
- located near root of nerve IX
- excites inspiratory muscles + sets eupnoea
- becomes dormant during expiration
what is the ventral respiratory group (VRG) involved in?
forced inspiration + expiration
what is depth of breathing determined by?
how actively respiratory centre stimulates respiratory muscles
what is rate of breathing determined by?
how long inspiratory centre = active
pulmonary irritant reflexes
irritants promote reflexive constriction of air passages
inflation reflex (hering-breuer)
stretch receptors in lungs stimulated by lung inflation
upon inflation, what happens?
inhibitory signals sent to medullary inspiration centre to end inhalation + allow expiration
hypothalamic controls act through …
limbic system to modify rate + depth of respiration
rise in body temp acts to ….
inc resp rate
cortical controls are …
direct signals from cerebral motor cortex that bypass medullary controls
changing pco2 levels are monitored by …
central chemoreceptors of brain stem
co2 in blood diffuses into cerebrospinal fluid
what does hypercapnia result in (inc in pco2)?
- inc in h+ conc in medulla
- stimulates DRG to inc depth + rate of breathing
- allows body to remove co2
depth + rate of breathing : pco2
process
- inc in arterial pco2
- dec ph in cerebrospinal fluid
- central chemo receptors in medulla mediate response
—> afferent impulses —> medulla respiratory centres
—> efferent impulses —> respiratory muscles
inc ventilation
arterial pco2, ph return to normal
what is the arch of the aorta?
main vessel originating from heart
what is the carotid sinus?
main artery of neck
where are the peripheral chemoreceptors located ?
- arch of aorta
- carotid sinus
decrease in po2 will stimulate DRG to…
inc resp rate
hypoventilation occurs when…
pco2 levels = abnormally low
body slows resp rate
what is a simple way to overcome hypoventilation?
holding breath/breathing slow and shallow
will cause co2 levels to rise in blood
as co2 levels rise, chemoreceptors triggered to stimulate DRG to inc ventilation
what may occur until pco2 levels rise?
apnoea (breathing cessation)
hyperventilation occurs when …
co2 removed from blood quickly
occurs in response to hyercapnia (high co2 in blood)
regulated by h+ conc in brain
what does hyperventilation reduce?
H+ (acid)
hypoventilation pushes reaction to …
right
respiratory alkalosis has a ph of ..
> 7.35
what are arterial oxygen levels monitored by?
aortic + carotid bodies
what is a hypoxic drive?
when po2 levels become principle respiratory stimulus
what are the causes of hypoxia?
reduced levels of oxygen in blood
hypoxic hypoxia
due to not enough pulmonary gas exchange
- high altitudes, drowning, aspiration, CO poisoning etc
ischaemic hypoxia
inadequate circulation
- diabetes mellitus, atherosclerosis
anaemic hypoxia
anaemia
- diet, internal bleed
histotoxic hypoxia
metabolic poison
cyanid poisoning
what are the signs of cyanosis?
- blueness of skin, lips, finger nail clubbing
quick travel to altitudes above 8000 feet may produce symptoms of acute mountain sickness
give eg of some symptoms?
- headaches
- shortness of breath
- nausea
- dizziness
how does acclimatisation to high altitudes occur?
chemoreceptors = more responsive to pco2 when po2 declines
decline in blood o2, stimulates kidneys to acerbate prod of EPO (erythropoietin)
what are common features of homeostatic imbalance?
- COPD
- history of smoking
- dyspnoea (laboured breathing)
- coughing + frequent pulmonary infections
- hypoventilation with respiratory acidosis
what is emphysema?
destruction of alveolar walls, loss of lung elasticity, air trapping
