Topic 13: Respiratory System - Control of Respiration Flashcards
What is the function of the respiratory centres in Medulla?
- set rate, depth and rhythm of breathing
What are the 2 groups of neurons in the respiratory centres of the medulla?
- ventral (VRG)
- dorsal (DRG) respiratory groups
What are ventral respiratory groups? (2)
- generates rate
- expiratory and inspiratory neurons
What do dorsal respiratory groups do? (2)
- receive chemoreceptor input
- modifies VRG output
What do Inspiratory neurons do? (3)
- send impulses down spinal cord to:
- phrenic nerve (innervates diaphragm)
- thoracic nerve (innervates external intercostals)
What do expiratory neurons do?
- fire to inhibit inspiratory neurons and expiration occurs passively
What occurs in quiet breathing (4)
1) inspiratory neurons active for 2 seconds during inspiration
2) expiratory neurons inhibit inspiratory neurons’ output for 3 seconds for expiration
3) VRG active for forced inspiration and exp. to recruit more muscles
4) respiration may cease if VRG damaged or suppressed from alcohol, morphine, etc.
What is the function of pontine respiratory centers?
- work with medullary centers to make breathing smooth
What happens if there is damage to pontine respiratory centers?
- gasping, irregular breathing
What other factors affect breathing?
1) lung stretch receptors
2) Voluntary control
3) Chemical control (chemoreceptors)
Where are lung stretch receptors found?
- in sm. muscle of bronchi and bronchioles
The lung stretch receptors include the Hering-Breur reflex. Recite the diagram
Why does voluntary control affect breathing? (3)
- primary motor cortex to skeletal muscle (corticospinal pathway) bypasses the medulla
- if medulla is damaged, you must remember to breathe
- when you hold your breath, it increases PCO2 so medulla overrides voluntary control to breathe
What are peripheral chemoreceptors? (3)
- carotid and aortic bodies
- weakly sensitive to PCO2
- very sensitive to H+
What do peripheral receptors do if there is an increase in blood H+ (decrease in pH)? (2)
- increases ventilation rate (vice versa)
- recall that if blood is buffered, it takes a large change in H+ to change pH
What do peripheral receptors do in relation to PO2? (2)
- stimulates receptors when PO2 reaches around 50-60 mmHg (end of plateau of Hb-O2 curve) - emergency situation
- decreased PO2 due to lung disease, low atm PO2
What are central chemoreceptors? (2)
- medulla oblongata
- DOMINANT CONTROL
Central chemoreceptors respond ___ to P__. What number is the resting arterial PCO2?
- indirectly
- CO2
- resting arterial PCO2 = 40 mmHg (set point 37-43 mmHg)
What process (reaction) involves central chemoreceptors? (3)
- CO2 crosses blood-brain barrier easily, H+ and HCO3- do not
1) in CSF, CO2 + H2O -> H2CO3 -> H+ + HCO3- - CSF is poorly buffered so there is a small change stimulus response
Other factors controlling breathing diagram
