Respiratory Physiology: Ventilation Control Flashcards
Ventilation control require stimulation of what muscles during inspiration
Skeletal
Where does ventilation control occur via
Phrenic (to diaphragm) and intercostal nerves (to external intercostal muscles)
Where does ventilation control reside
ill-defined centres located in the pons and medulla
What is PRG and what does it modulate
Pontine respiratory group located in the Pons and it modulates DRG and VRG
What does VRG and DRG stand for
Ventral Respiratory Group and Dorsal Respiratory Group
What does VRG control
Expiration (tongue, pharynx and larynx)
What does DRG control
Inspiration (via phrenic and intercostal muscles)
What are the 4 basis’ of rhythm of respiration
- Emotion (via limbic system)
- Voluntary over-ride (via higher centres in the brain)
- Mechano-sensory input from the thorax (stretch reflex to prevent over-expansion)
- Chemoreceptors which detect chemical composition of the blood (PCO2, PO2 and PH)
Which of the 4 basis of rhythm is the most significant
Chemoreceptors
Where is the central chemoreceptor located
Medulla
What is the stimuli which activates the central chemoreceptor
Responds directly to H+ (directly reflects PCO2)
Where do these changes occur and how does this effect the ventilatory drive
Occurs in the CSF. CO2 combines with H20 to form carbonic acid and H+ and is the primary ventilatory drive
Hypercapnea
Raised PCO2 in CSF
Does the central chemoreceptor respond directly to changes in the plasma (Y/N)
N
What crosses the blood brain barrier when PCO2 in arterial blood increases?
H+
Where are the peripheral Chemoreceptors located
Carotid and Aortic bodies
What is the stimuli which activates the peripheral chemoreceptor
Responds primarily to plasma [H+} and PO2 and is the secondary ventilation drive
What happens if plasma pH falls [H+ increases]
Acidosis, ventilation is stimulated
What happens if plasma pH increases [H+ falls]
Alkalosis, vomiting and ventilation will be inhibited
Common drugs affecting respiratory centres
Barbiturates and Opioids
Gaseous anaesthetic agents
Nitrous Oxide
How do Barbiturates and Opioids effect Respiratory Centres
They depress respiratory centres that can lead to respiratory failure
How do gaseous anaesthetic agents effect Respiratory Centres
Increase RR but decrease Tidal Volume so decrease Alveolar Ventilation
How does nitrous oxide effect the respiratory centres
blunts peripheral chemoreceptors response to falling arterial oxygen
