Exam #4: Regulation of Respiration Flashcards
What four centers/structures help to control breathing?
- Control centers in brainstem
- Chemoreceptors
- Mechanoreceptors
- Respiratory muscles
What are the six respiratory centers in the brain stem?
- Ventral Respiratory Group (VRG)
- Dorsal Respiratory Group (DRG)
- Pre-Bötzinger Complex (PBC)
- Pneumotaxic Center
- Apneustic Center
- Cerebral Cortex
What two types of neurons are found in the Ventral Respiratory Group (VRG)? Which type dominates?
Inspiratory AND expiratory
- Expiratory dominate
Under what conditions is the Ventral Respiratory Group (VRG) most active?
Exercise (increased ventilation demands)
- Use of ACTIVE expiratory neurons
What type of neuron is found in the Dorsal Respiratory Group (DRG)?
Inspiratory neurons only
What occurs when the Dorsal Respiratory Group (DRG) stops firing?
When inspiratory neurons stop firing, inspiratory muscles relax, and passive expiration occurs
What is the role of the Pre-Bötzinger Complex (PBC)? How does it do this?
Sets frequency of inspiration
- Does so by driving the rate of rhythmic firing of inspiratory nerves in the DRG
What two things can inhibit the activity of the Pre-Bötzinger Complex (PBC)?
- Propofol
- Opioids
What is the role of the Pneumotaxic Center? How does it do this?
Turns off inspiration by limiting APs of Phrenic n. to diaphragm (aka switches off inspiratory nerves)
What is Apneusis?
ABNORMAL breathing pattern of prolonged inspiratory gasps then brief expiratory movement
What is the role of the Apneustic Center? How does it do this?
Excites inspiratory center in medulla → prolonged inspiration via prolonged APs in phrenic nerve = prolonged diaphragm contraction
What two things can induce the Apneustic Center?
- Ketamine
- TBI
What is the role of the Cerebral Cortex? What are two examples of what this looks like?
Voluntary control of breathing
- Voluntary hypoventilation/breath holding
- Voluntary hyperventilation
What does voluntary hypoventilation mean for PaO2 and PaCO2?
Decreased PaO2 → increased PaCO2
What does voluntary hyperventilation mean for PaCO2 and pH?
Decreased PaCO2 → increased pH
What is the most important determinant for chemoreceptors, and why is this?
PaCO2 is MOST important
- Rate and depth of breathing are regulated to keep PaCO2 at 40 mmHg
How is ventilation affected by PaCO2 levels during wake state? What about in sleep state?
- In wake state, ventilation is unaffected by PaCO2 less than 40 mmHg BUT >40 mmHg causes hyperventilation to get it back to set point/normal
- In sleep state, ventilation is unaffected even if PaCO2 levels increase ABOVE 40 mmHg
Why does sleep state cause a shift to the right of the ventilation/PaCO2 graph?
What three other things can cause a shift to the right?
Slope is decreased due to decreased sensitivity to CO2 changes
- Narcotics, alcohol and anesthetics can also cause a shift to the right
What is the MOST important type of regulator? Why are they most important (i.e. what is their role)?
Central Chemoreceptors
- Keep PaCO2 within normal range
What are brain stem Central Chemoreceptors more sensitive to changes in?
pH of CSF
If pH is increased, what will brain stem Central Chemoreceptors induce?
Hypoventilation
- Increased pH → less CO2 → decreased breathing rate
If pH is decreased, what will brain stem Central Chemoreceptors induce?
Hyperventilation
- Decreased pH → more CO2 → increased breathing rate (to expel the CO2)
What do medullary Central Chemoreceptors respond directly to? Indirectly to?
- Directly: change in pH of CSF
- Indirectly: change in PaCO2
What are the two types of chemoreceptors? Where is each located (2)?
- Central Chemoreceptors: brain stem, medulla
- Peripheral Chemoreceptors: aortic bodies, carotid bodies
Under what two conditions do Peripheral Chemoreceptors induce hyperventilation?
- Decrease in PaO2 less than 60 mmHg
- Decrease in arterial pH
What is the ONLY type of Peripheral Chemoreceptor responsible for detecting a decrease in arterial pH?
Carotid bodies only
What are the four types of mechanoreceptors?
- Lung Stretch Receptors
- Joint & Muscle Stretch Receptors
- Irritant Receptors
- Juxtacapillary (J) Receptors
Where are Lung Stretch Receptors located? What are they activated by, and what do they induce?
- Located in airway smooth muscle
- Activated by lung/airway distention (Hering-Breuer reflex)
- DECREASED breathing rate (hypoventilation)
Where are Joint & Muscle Receptors located? What are they activated by, and what do they induce?
- Located in joints and muscles
- Activated by limb movement
- INCREASED breathing rate (hyperventilation)
Where are Irritant Receptors located? What are they activated by, and what do they induce?
- Located between epithelial cells lining airways
- Activated by dust/pollen
- INCREASED breathing rate (hyperventilation)
Where are Juxtacapillary (J) Receptors located? What are they activated by, and what do they induce?
- Located in alveolar walls
- Activated by engorgement of pulmonary capillaries
- INCREASED breathing rate (hyperventilation)
Why is hyperventilation induced with activation of Irritant Receptors?
Increased breathing rate via bronchial smooth muscle constriction
Why is hyperventilation induced with activation of Juxtacapillary (J) Receptors?
Increased breathing rate due to increased BF
What are the two types of apnea? Which has NO effect on PaO2 or PaCO2, and why?
- Brief sleep apnea: NO effect on PaO2 or PaCO2 because TOO SHORT
- Prolonged apnea
What are the two subtypes of prolonged apnea? Which one presents with pleural pressure oscillations?
- Central sleep apnea: NO pleural pressure oscillations
- Obstructive sleep apnea: pleural pressure oscillations present
What is the most common type of sleep apnea, and what is a risk factor associated with it?
Obstructive sleep apnea
- Obesity is a risk factor
What does the presence of pleural pressure oscillations indicate?
Lungs ARE trying to expel high CO2 levels
