breathing regulation

Question 1

what must generation of all rhythms include ?

Answer 1

• maintenance of IV breathing
• adjustment of ventilation for adequate GE
• also adjustment of pattern for activities such as speech and swallowing (this requires V control)

Question 2

what is the central pattern generator?

Answer 2

• PONS (pontine respiratory group)

- medulla (medullary resp centre)

Question 3

what does the PRG do?

Answer 3

• interacts with the medullary centres to smooth respiratory rhythm (timing)
• medulla important for rhythm generation (no R generated after transection)
• influences switching between inspiration and expiration

Question 4

what is the function of the DRG?

Answer 4

• exclusively inspiratory neurones
• located in the NTS
• integrates info from chemo/ mechanical R afferents related to breathing

Question 5

what is the function of the VRG ?

Answer 5

• inspiratory and expiratory neurones

- activity here excites the inspiratory DRG neurones and inhibits the expiratory VRG neurones

Question 6

outline what happens during quiet inspiration

Answer 6

-The DRG -> self excitable N generate APs –> inspiration

• excitable activity down the cervical spinal cord –> contraction of diaphragm
• VRG inactive

Question 7

outline what happens during quiet expiration

Answer 7

• entirely passive process
• cyclic activity of DRG responsible (DRG on/ off)
• relaxation of D –> passive recoil

Question 8

what happens where there is an increased demand for ventilation to match metabolism ? (I)

Answer 8

• sensory afferents reach NTS (rate of met)
• NTS–> DRG –> more active –> D contracts with greater force –> forced inspiration
• the VRG is also activated this time by the NTS –> efferents via TSC–> contraction and recruitment of other respiratory muscles

Question 9

the NTS?

Answer 9

• receives sensory afferents regarding Co2/ O2 from carotid bodies

Question 10

what happens when there is a increased demand for ventilation ? (E)

Answer 10

• The DRG is inactive
• VRG neurones inactive
• involvement of the BOTZ
• this inhibits the DRG/ VRG –> causing relaxation of D and the other muscles which were recruited
• but the BOTZ also causes other expiratory muscles to contract (excites) –> other VRG neurones activated leading to a more forceful expiration

Question 11

explain how voluntary control can influence breathing

Answer 11

• neurones from the cerebral cortex (motor, limbic, hypoT) can travel directly to the SC bypassing the medullary and PONS centres
• voluntary suppression of inspiratory neurones in DRG
• occurs during large breaths, hyperventilation, speaking , swallowing and breath holds

Question 12

where is pacemaker generation seen?

Answer 12

• within the medulla
• PreBotC cells
• spontaneous AP generation during low ECF calcium
• rhythmic activity linked to respiratory cycle
• site of rhythm generation