Lecture 21- control of breathing Flashcards
Where are central chemoreceptors found?
just beneath the surface of the medulla
What are central chemoreceptors stimulated by?
High CO2, low pH in the CSF.
OXYGEN HAS NO EFFECT
Why doesn’t the csf resist pH changes from the blood?
CO2 is lipid soluble so crosses the blood-brain barrier. The CSF is only weakly buffered so the pH changes as the blood does.
What do peripheral chemoreceptors detect?
Changes in pH, PCO2 and PO2
peripheral do detect oxygen changes
Where are peripheral chemoreceptors found? What is each innervated by?
- Carotid body- (at bifurcations of carotid arteries)- innervated by carotid sinus nerve via glossapharyngeal.
- Aortic Bodies- above and below the aortic arch- innervated by the vagus nerve.
What are the 3 parts of local control of gas transport that work together?
- PO2 and PCO2 in active tissue- vasodilation etc.
- Lung perfusion- vasoconstrcition in low O2 part of lungs
- Alveolar ventilation- Bronchodilatioin when high CO2 so it’s exhaled.
what is repiratory acidosis?
When pH is below 7.35. Because of very high carbon dioxide levels
What is respiratory alkalosis?
pH above 7.45. Because of hyperventialtion, very low CO2 levels
What are the dangers of breathing oxygen- rich gases?
PO2 too high. Generates free radicals- leads to coma and death
What are the 3 types of mechanoreceptors?
- Slowly adapting stretch receptors. Hering-Breuer reflex.
- Rapidly adapting stretch recpetors. Coughing reflex
- C-fibres receptors (J receptors)- chemical/mechanical stimuli, sends signals, brachoconstriction.
What are the main parts of the central controlller for breathing?
- Rythmicity centre (medulla)- controls automatic breathing
- PONS- (pneumotaxic and apneustic centres) modify firing patterns of medulla
What are DRG and VRG and what do they do?
Dorsal respiratory group and ventral respiratory group.
DRG fires I neurons during in Inspiration
VRG fires _E _and I** neurons during **expiration
I neurons set rythm for quiet inspiration (stimulate muscles). E neurons, passive process. E neurons inhibit I neurons.
What are the parts of the PONS?
- Apneustic centre- promotes inspiration, stimulates the I neurons- increases intensity of inspiration
- Pneumotaxic centre- inhibits apneustic centre- stops inhalation, promotes exhalation