Control of breating Flashcards by Alexi Cross

What is the function of the Dorsal Resp Group (DRG)?

Determines timing of resp cycle

(PSR activation each inspiration = rhythmic pattern of breathing)

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What are the effectors activated by the DRG?

Diaphragm and Ext intercostal muscles

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What is the function of the Ventral Respiratory Group? *(VRG)

Contributes to extra resp drive in cases of increased demand

Coordinates info from cortical input, peripheral sensory info and visceral and cardiovascular inputs

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what resp functions does the VRG NOT do?

inactive during normal quite breathing
doesn’t generate resp rythym

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What is the innervation of the DRG and VRG respectively?

DRG= Pulmonary stretch receptors and mechanoreceptors

VRG= chemoreceptors and higher brain centres

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what are the components of the VRG and what neurons are they responsible for?

Botzinger complex and Casual VRG = expiratory neurons

Rostral VRG = inspiratory neurons

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how can the inspiratory ramp be altered?

1- Rate (lung V/Depth) (signal intensity)

2- Termination point (freq)

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What is the inspiratory ramp signal?

cyclical cycle (2s duration, 3s pause) of increased DRG and VRG to allow for controlled lung filling.

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What is the purpose of the pause in the inspiratory lung ramp?

passive exhalation via elastic recoil of chest wall and lungs

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What is the pre-botzinger complex and where is it?

Needed for rhythmogenesis and signals DRG

It is in the VRG but is FUNCTIOANLLY SEPARATE

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What is rhythmogenesis?

removal of rhythmic inspiratory activity

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Explain the cycle of quiet breathing

Insp muscles contract –> inspiration –> DRG inhibited –> insp muscles relax –> passiv expir –> DRG active

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Explain the cycle of forced breathing

insp muscles contract, exp relax –> inspiration –> DRG and insp centre of VRG inhibited, Exp centre of VRG active

–> insp relax, exp contract –> active expiration –>

DRH and insp centre of VRG active and Exp centre of VRH inhibited –>

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PRG vs DRG and VRG

DRG and VRG = generates reso rythym

PRG = fine control of resp rythym

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What is the function of the Apneustic centre and Pneumotaxic centre respectively?

A= Prolongs resp = increased Vt and decreased f

P= Ramp off earlier = decreased Vt and increased f

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How does cortical override work?

may bypass the medullary respiratory centre to act directly on respiratory muscle LMNs

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Role of Upper Resp tract in reflexes

Contains receptors in nose, pharynx and larynx that are sensitive to toxins, irritants and temp

Origin of cough reflex

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What are the two types of pulmonary stretch receptors and what are they sensitive to?

Slowly adapting stretch receptors (SARs) =
Lung volume

Rapidly adapting stretch receptors (RARs) =

Changes in Vt, f or Cl
Nociceptive and chemosenstitive

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What is the role of the Hering-Breuer inflation reflex?

Inhibits inspiration in response to increased Pulmonary transmural pressure gradient (increased Lung stretch)

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Where are the TASK-2 and GPR4 chemoreceptors located?

RTN neurons

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Describe the action of RTN neurons

selectively target pon-to-medullary region to help generate resp rythym and pattern

What are the two peripheral chemoreceptors and what nerves do they use to input into medulla?

Aortic bodies
Vagus nerve

Carotid bodies
Glossopharyngeal nerve

What are the peripheral chemoreceptors most sensitive to?

Changes in arterial H+

Non-CO2 generated H+

Most sensitive to low PaO2

What effects do the peripheral chemoreceptors have?

Increase rate and depth of breathing

Bradycardia

HTN

Increased bronchomotor tone and adrenal secretion

Describe the flow of events that occurs when there is increased Arterial PCO2

arterial chemoreceptors stimulated --> DRG stimulated --> increased f --> increased elimination of Co2 --> decreased P arteial CO2 --> homeostasis restored

What does increased CO2 have a stronger acute effect than chronic effect?

renal mechanisms increase blood HCO3 HCO3 crosses BB and binds to H = decreased CSF

What is the advantage of fainting?

horizontal position = heart doesn't have to pump against gravity to maintain cerebral perfusion

What is Owles point?

Point when relative hyperventilation is associated with lactic acidosis

Describe the Ventilatory response to light-mod exercise

Arterial Blood gases stable Increased VE matched w increased VO2

Describe the Ventilatory response to heavy exercise

Increased VE > increased Vo2

What is Primary Hypoventilation Syndrome (Ondine's curse)

Long periods of apnoea even whilst awake Might die during sleep due to lack of automatic resp control in sleep.

What is the cause and management of Pri Hypoventilation Syndrome?

Cause Congenital (PHOX2B mutation) Acquired post brain injury management Mechanical ventilation Diaphragmatic pacing

what is Cheyne-Strokes Respiration and who does it often impact?

Periodic breathing abnormality that occurs in high altitide or in preterm newborns. Cycles every 40-60s

What causes central sleep apnoea?

transient pause in central drive to breath

How does the preBotC aid with arousal?

Rebreathing exhale air during prone sleeping Altered blood gases initiates arousal response Successful arousal = head lifting and repositioning

How does preBotC aid with Autoresuscutation?

If arousal fails = more sevre hypoxic stare Transition to gasping mediated by preBotC Gasping = arousal

How does impaired pre-Bötzinger complex function lead to SIDS?

impaired sigh and gasp generation → irreversible hypoxic insult → asphyxiation

What is the presentation of CO poisioning?

Non-specific (headaches, fatigue, malaise, confusion nausea, chets pain and SOB). Late stage = cherry-red lips, peripheral cyanosis and retinal haemorrhages

What impact does CO poisoning have on the Oxygen-Hb dissociation curve?

Downward shift: CO displaces O2 from Hb = decreased HbO2 sat Left Shift: CO increases affinity of Hb for O2 = deceased O2 unloading

How do opioids cause respiratory depression?

Depresses Resp Rythym Decreased sensitivity of peripheral chemoreceptors to hypercapnia and hypoxia Increased Up airway res Decreased lung complaince

What opioid receptor subtype controls resp?

Mu-opioid receptor (MOPr) controls resp via MOP B-arrestin pathway

where does DRG send out put to?

Phrenic motor neurons for diaphragm contraction spinal interneurons (C1-2) for ext intercostal muscles VRG and PRG

where does the rVRG receive input from?

PreBotC DRG PRG Chemoreceptors High Brain centres

Where does the cVRG recieve input from?

PreBotC rVRG PRG Chemoreceptors High Brain centres

Where does the BotC recieve input from?

Nucleus Tracts Solitus (info from chemoreceptors) DRG r + c VRG PreBotC

Where does the rVRG send an output to?

phrenic motor neurons (activate) thoracic motor neurons PreBotC and BotC

Where does the cVRG send an output to?

abdominal motor neurons internal IC motor neurons BotC and NTS

Where does the BotC send an output to?

Phrenic motor neurons (inhibits) PreBotC rVRG/cVRG

What is Corticol control of breathing and what limits it?

voluntary conscious control of breathing If hold breath (trying to control) will decrease PoO2 and increased PCO2. The increase in PCO2 creates gasping (involunteyr via PreBoT) the increased CO2 is detected by chemoreceptors (increased HCO3 = crosses BBB and binds H+)

what is the indirect and direct impact of Increased PaCO2?

indirect = medulla RTH (central CR detects CSF H+) direct = stimulates peripheral CRs

acute vs chronic PaCO2 effect on resp drive.

Acute = strong -central = rapid -peripheral = elevated PaCO2 amplitude Chronic= weak -kidneys adapt to chronic hypercapnia as HCO3 buffers H+ -desensitises chemoreceptors

explain the glomerular filtration?

blood enters glomerlus via afferent arterioles --> Pressures force water through the GFB. PGC does filtration whilst capsular and blood calcioid P opposes filtrate.

Control of breating Flashcards

wk 6