B2- Control Of Breathing Flashcards
What is minute ventilation litees per minute
5L per min
What is maximum minute ventilation eg in exercise
125-175 L per min = ventilatory reserve
What is arterial ph at usuallt unless resp acidosis or alkilosis
7.35-7.45
If alveolar p02 is around 159, what is arteiral
Around 100 mm hg (40 in tissues)
Ppco2 is lower in arrtial than tissues. Around what
35-40 compared to 46 mm hg in tissues
At sea lecel what is toral mmhg bsrometeic oressure
760 (around 160 for o2/21%)
What is the p h20 (humidity constant) which redcues the 760mmhg and therefore reduces p02 in alceoli too
47 = 713 mmhg instead
If o2 is arounr 21% of baromemetric pressure what is it includin humidity
150 vs 159 if not humid air
Since barometric pressure decreases when go ip in altitude whag also decreases
P02
When do hb on dissocion curve get to 75% saturation (wuite tolerant of low mmhg)
40mmhg (venous blood)
Where does it start to rapidly dissoxate
At tissues eg around 50% dissocation when at p02 of 27
Why is saturation at wuite low altitudes good for
People living in high altitude as you sont wanr dissocation without pick up
How does co2 affect dissociation
Infeeases if it reacts with h20 and then forms h and hco via carbonic anhydrase
H binds hb and causes taut state (deox) instwad of relaxed (bohr effect)
What is the respiratory centre of control
Medulla oblongata in brsin stem
What sort of signals do they get (afferent)
Chemoreceptor signals, proprioceptors, stretch recetors, irritant
Where are the main chemoreceptors
Central. They ste in medulla
What are drg neurones (during quiet)
Mainly inspiratory. They send signals eg down ohrenic to diaphragm snd then external intercostals too
Bow do inputs fet to drg
Vagus and IX mainly
What are vrg in ONLY sctive resp
Both insp and exp neurones eg to pahrynx larynx diaphragm and external intercostals
Then internal and abdomjnals for expiration
What does rhe pons do
Modify outputs by the medulla
What do central mainly snese
Co2, ph
What can cross from blood freely to csf reaching central chemorecetors
Co2
What does co2 react with ti form the h and hco (h does this) which allows centrak to respond
H20 and carbonic anhydrase reaction
What does co2 have to be above to cause central chemo to upreg ventilation
40 mm hg (sensitive ti hypercapnia)
What cant cross freelyb
H and HCO
Which layer of endothelial acts as the bbb shrrounding capillaries
Choroid plexus
How does cp allow transport of ions like hco, na and cl across their villi into ventrciles (cerebral ventricles)
Acgive transport. Not free movemrnt
Why cant central control resp acidosis and what does detect it
Cant detect ph as well in the blood as well(limited to csf). Peripheral detect co2 to an extent too = stop acidosis
Peripehrral detecting o2 are not sensitive. At what o2 legel do they respond
Below 60mmhg
What % of respiratory drive do they have for co2/ph eg in acidosis
20%. It is weak stimulating
Are rhey essential
No
Where are cwrotid bodies and what do they send impulses down
Carotid sinus. Send down ix
Aortic down x
What happens at high o2 to peripheral
Switch off and centilation stops for abit till ph lwoers and central can respond
How do type1 glomus cells in carotid body respond
Detect low o2 and causes k channels to close. This causes depolarisation and ca floods in.
Ca flooding causes dopamine release down ix
