Respiratory system - Acid base balance adn central control Flashcards
What is the rhythm and depth of our breathing set by?
the central pattern generator (CPG) = Pacemaker neurones in the medulla oblongata
What is the central pattern generator?
A network of communicating pathways which work to produce an appropriate respiratory rate and depth based on neeed
What innervates muscles of inspiration
neurones of the dorsal respiratory group which stimulate motor neurones innovating muscles of inspiration: diaphragm and external intercostal
What stops us breathing in?
Hering-Breuer Reflex: Stretch receptors in our lung and thoracic cage = turns off stimulation of dorsal respiratory group = inspiration muscles stop contracting and recoil occurs
When fully expanded what happens
Hering breuer reflex means that the rate of impulses increases so lungs stop expanding.
During active expiration what neurones involved?
Neruones in the ventral respiratory group send impulses to expiratory muscles (Internal intercostal muscles and abdominal muscles)
Where in the brain is the medulla oblongata?
Last part of brain stem before spinal cord- where respiratory centre is
What two parts of the brain control respiration
Receptors that send impulses for Hering Breuer reflex send to pons (switch off dorsal resp group) = just infront of MO = two communicate to control repsiration
What si the role of pulmonary stretch receptors
make u stop breathing before you burst!
Where does conscious of breathing come from?
Cortex of brain = to change breathing pattern = deep, slowly etc
If breath in irritant what happens
Irritant receptors detect = causes you to hold breath = reduce depth of breathing = so won’t go into lungs
Where are the locations of peripheral chemoreceptors.
What do they monitor
What is their innovation
- Carotid and aortic arteries (same as baro that measure BP) = not same!
- Called carotid and aortic bodies, monitor PaO2, PaCO2 (most important) and arterial [H+] IN ARTERIOL BLOOD!
- High blood supply
- Innovated C = cranial nerve 9. A = cranial nerve 10
What does the conc of H+ ions tell us about respiration function?
Indicated CO2 conc. CO2 is carried by carbonate = has a H+
Also indicates if there is a problem elsewhere!
What to remember about aortic bodies
More important in foetus, not v active in adult
Carotid bodies detecting changes, more sensitive in CO2 or O2 changes?
- CO2 changes
- Because of the oxygen dissociation curve: Oxygen level has to drop quite a lot before Hb starts to become desaturated. Carotid bodies don’t detect until ppO2 dropped to about 70% = serious loss of resp function before carotid bodies activated!
Where are central chemoreceptors and what do they monitor?
What is important about this?
- BRAIN
- PaCO2 only: CO2 crosses blood brain barrier, carbonic anhydrase acts to convert to bicarbonate and H+ = reflects arteriole Pa CO2.
- the Pa CO2 detected by central chemoreceptors is the most important factor governing the respiration under normal circumstances as PaO2 less sensititve as HB saturation nearly 100% until PaO2 drops below 70mmHg
What is normal blood pH?
7.35-7.45
What is acidosis
Decrease in extracellular fluid BELOW 7.35
What is alkalosis
Increase in extracellular fluid OVER 7.45
What is the Extracellular fluid?
Interstitial fluid + plasma
How does the body rebalance an alkalosis?
increase [H+] in ECF, oppo for acidosis.
3 mechanisms:
1st line = BUFFERING: free H+ binds to something = quick but limited capacity
2nd line = Lungs = greater capacity = retain CO2 = breath less or breath out more CO” = use up H+ and get rid
3rd line = kidneys = HUGE range, longer time to kick in
What type of acid is CO2
NOT an acid but a POTENTIAL acid = causes the creation of an acid (carbonic)
What is respiratory acidosis
Accumulation of H+ due to a build up of CO2
What is metabolic acidosis
Accumulation og H+ due to build up of fixed acids e.g. H2PO4
What is the equation to remember?
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
What will happen to the buffering equation in order to compensate for a metabolic acidosis?
- Higher conc free H+ in blood
- equation will shift to LHS
- so respiration will be deeper and more quickly to remove CO2 = can take on more H+ to make mroe CO2
What will happen to buffering equation in order to compensate for a metabolic alkalosis?
- dec conc free H+ in blood
2. breath more slowly and less deeply to retain CO2 in lungs in order to “give” mroe free H+
What is the best kind of buffer
Weak acid as dissociates incompletely, strong acid = complete = useless
If bicarbonate levels go up what happens to pH and H+
H+ UP (one bicarbonate for every H
pH DOWN
Why do we measure the levels of bicarbonate of the blood?
The level can tell us if the problem is acute- just happened, or chronic = renal compensation
What would occur to the bicarbonate level in compensated respiratory acidosis
Respiratory acidosis = retaining CO2. H+ inc, pH down, HCO3- (bicarbonate) inc.
Kidney compensate = create lots of bicarbonate, wee out H+.
pH back to normal but bicarbonate levels SKY HIGH.
Compensated respiratory alkalosis what happens to bicarbonate level
decreases to be v low
If CO2 can’t be exhaled adequately what will be the result in terms of acid:base balance. Explain
- Respiratory ACIDOSIS
- Retaining CO2, means more CO2 binds with water under the influence of carbonic anhydrase to give carbonic acid which dissociates into bicarbonate and H+.
- Inc production of H+ lowers pH
