Pulmonary 8 - Lecture 30 Flashcards
What are the 3 phases of breathing?
- Inspiratory Airflow
- Expiratory Airflow
- Expiratory Apnea
What happens to the frequency of breathing during exercise? Tidal Volume?
Frequency increases due to a decrease in pause time
- Tidal Volume increases by accessing the inspiratory reserve and expiratory reserve capacities
Is breathing automatic or voluntary?
BOTH
Automatic via Medulla
Voluntary via Motor Cortex (CST)
ex: hypo/hyperventilation
Where is the respiratory control center located?
The medulla
What respiratory group of the MEDULLA controls inspiratory neurons only? Both inspiratory and expiratory?
- Dorsal Respiratory Group (DRG)
= inspiration only
- N. Solitarius - Ventral Respiratory Group
- BOTH inspiration & expiration
What part of the brain GENERATES the breathing Pattern? What part of the brain CONTROLS the breathing pattern?
- Medulla
2. Pons
What are the functions of the
- Apneustic Center
- Pneumotaxic Center
Which part of the brainstem do these neurons belong to?
- Apneustic = excitatory effect on DRG (inspiration)
2. Pneumotacic = inhibits DRG
suppresses inspiration
Describe the following for CENTRAL chemoreceptors:
- Location
- Sensitive to changes in what?
- Insensitive to changes in what?
BBB:
- Permeable to
- Impermeable to
- Ventrolateral surface of Medulla Oblongata
- Sensitive to CO2 changes via pH changes in CSF
- Insensitive to pO2 changes
- permeable to CO2
- Impermeable to H+ and HCO3-
Why is the CSF so sensitive to changes in pCO2?
CSF has relatively low protein concentration so the decrease in pH and increase in CO2 is easily detected by the CSF chemoreceptors (more favorable environment than arterial CO2)
- pCO2 changes within minutes
Reducing the pH of CSF increases or decreases firing rate?
Increases firing rate
Describe the following for PERIPHERAL chemoreceptors:
- Location
- Sensitive to changes in what?
- Insensitive to changes in what?
- Aortic/Carotid Bodies
- Sensitive to:
decrease in pO2
decrease in pH
increase in pCO2 - Hb concentration does not change the firing of peripheral chemoreceptors, only change sin partial pressures of dissolved O2 or CO2 generate a response
- low proportion of total ventilation response to CO2 (only 20-40%)
What are the only receptors that respond to changes in pO2?
When does robust firing of pCO2 occur? (what pO2 level)
Peripheral Chemoreceptors
- firing begins at small changes in pO2
ROBUST firing begins when pO2< 70-80 mmHg
Where are Pulmonary Stretch Receptors Located?
What inhibits and initiates respiratory activity in the Receptors?
(Hering- Breuer Inflation/Deflation Reflex)
How is this response generated? (via what nerve)
- Smooth muscle cells of airways
- INFLATION of lung inhibits activity of inspiratory muscles
DEFLATION of lung INITIATES activity
- Respond via VAGAL NERVE
- Hering- Breuer Inflation & Deflation Reflex*
- -> largely inactive in adults, except at HIGH TIDAL VOLUMES
- important in newborns
Describe the following for Irritant Receptors:
1. Location
2. Stimulated by
3. What nerve does the impulse travel via?
Clinical correlates?
- Between airway epithelial cells
- Stimulated by NOXIOUS gases, cigarette smoke, dust, and cold air
- Impulse via VAGUS nerve (just like the stretch receptors)
- May play a role in ASTHMA
What do J (Juxtacapillary) Receptors & Bronchial C fibers respond to?
Respond to chemicals injected into the pulmonary (J receptors) & Bronchial (C fiber circulation)
What are some other receptors involved in breathing control? (4)1
- Nose/ upper airway receptors (irritant receptors)
- Joint/muscle receptors
- Pain/temp receptors
- Arterial Baroreceptors
What happens to the CO2 response curve as alveolar CO2 increases?
Slope INCREASES (at low O2; but at high O2 the slope is not as great)
thus breathing frequency increases
If PaO2 is kept normal, what happens to ventilation as pCO2 increases? If PaCO2 is reduced, how does ventilation change?
Ventilation increases by 2-3 L/min for every mmHg rise in PaCO2
- reduction in PaCO2 reduces the stimulus for ventilation
At a lower PaO2, what happens to:
- Ventilation at a given PaCO2
- Ventilatory Response to CO2 (slope)
- Ventilation is HIGHER
2. Ventilatory response INCREASES (steeper slope)
What happens when hyperventilation creates a situation of hypercapnia (low CO2)?
Breathing decreases because the CO2 is so low, ventilation needs to decrease
What do the following do to the Ventilatory Response to CO2:
- Sleep
- Aging
- Trained athletes/divers
- Drugs (morphine/anesthetics)
- Work of breathing increased (COPD)
REDUCE the ventilatory response!
What situation has the highest sensitivity to CO2 and the LOWEST threshold?
- Awake
- Sleep
- Drugs
- Metabolic Acidosis
Metabolic Acidosis
- steepest slope = INCREASED VENTILATORY RESPONDE
- lowest response threshold for Co2 increases (below 35)
At high PaCO2, ventilation begins to increase only if the PaO2 level drops below what?
100 mmHg
At low and normal PaCO2, what occurs to ventilation? What change in PaO2 must be achieved to begin increasing ventilation?
Ventilation increases if the PaO2 drops to 50-70 mmHg
- this is because the PaCO2 level is normal/ low resulting in a lower stimulus being sent to the chemoreceptors
- Ventilation does not increase until OXYGEN has fallen dramatically (if Co2 is still normal)
What type of simulation plays a small role in regulation of ventilation?
Hypoxic Stimulation (O2 RESPONSE!!)
What happens when patients with severe lung disease & chronic CO2 retention are placed on a respirator of 100% O2?
Because the HYPOXIC stimulus is the MAIN stimulus for ventilation, the patient’s signals to increase breathing rely mainly on the levels of O2
- if the O2 levels increase, breathing STOPs!
- Hypoxic Stimulus develops mainly as a result of chronic high CO2 –> abolishes the normal response stimulus, so the patient relies on O2 levels (instead of CO2 levels, as in normal individuals)
How does Metabolic Acidosis affect ventilation?
Increases ventilation, despite low PaCO2 levels
diabetes mellitus, kidney failure
Ventilatory responses to low pH are regulated by Peripheral or Central Chemoreceptors?
PERIPHERAL
What happens to the BBB at very low arterial pH?
BBB becomes partly permeable to H+
How do PaO2, PaCO2, and pH change with:
- Moderate Exercise
- Severe Exercise
Does ventilation increase in both cases?
- Levels do not change signfiicantly
- pH decreases in severe exercise since lactic acid is released (hits anaerobic threshold –> aerobic metabolism no longer provides sufficient energy)
VENTILATION INCREASES in both cases
What is the reason that anaerobic threshold is achieved? What happens here? When does this occur?
- Lactic Acidosis
2. VCo2 increases, Lactate Increases paO2 increases Ventilation Increases PaCO2 decreases pH decreases
- occurs at 1.5 L/min of O2
What happens to the following during OBSTRUCTIVE SLEEP APNEA:
- Airflow
- Pleural Pressure
TX?
- Airflow stops
- Pleural Pressure increases
- diaphragm is still functioning but air cannot flow due to obstruction
TX: CPAP (Continuous Positive Airway Pressure)
What happens to the following during Central Sleep Apnea:
- Airflow
- Pleural Pressure
- Airflow Stops
- Pleural Pressure stops
= DIAPHRAGM is not functioning
TX: can stimulate diaphragm to contract (like a pacemaker)
What type of breathing is the following:
Deep Breathing w/ normal or reduced frequency
-typical in severe acidosis
Kussmaul Breathing
What is Apneustic Respiration?
What input is lost?
- Sustained /long periods of inspiration, brief period of exhalation
- Vagal input & the Pneumotaxic center LOST
(no longer inhibiting the DRG center for inspiration, thus the Apneustic Center overstimulates DRG)
Result of: Brain Damage, Intoxication
Describe the causes of the following
- CHeyne-Stokes Ventilation
- Biot’s Respiration
- Brain injury, increased intracranial pressure, brain tumors encephalopathy
- has high frequency breathing followed by inspiratory pauses - Neuronal Damage
What can override the output of the Pons and Medulla?
Cortex
The response to pO2 is small when the pO2 is above 50-60 mmHg. True or False?
TRUE
