PULMONARY 08: CONTROL OF RESPIRATION Flashcards
What are the two main tasks that must happen for there to be control of respiration
- ) Establishment of automatic rhythmic breathing (via inspiratory muscles)
- ) Accomodation for changing demand, whether this be metabolic, postural/mechanical, or nonventilatory actions (like talking, coughing, etc where you would need to overcome autonomy to do them)
What is the order of control of respiration
A central controller leads to outputs in the driving muscles of inspiration, whose effects are interpreted by sensors that feed back to the CNS
Four major automatic sites of respiratory control
- Respiratory control center (ex. medulla)
- Central chemoreceptors (in CNS)
- Peripheral chemoreceptors (aortic arch, carotid sinus)
- pulmonary mechanoreceptors/sensory nerves
How does voluntary respiration take place?
Via routing though the motor cortex and corticospinal tracts
Control of respiration in the brainstem happens in what major areas
Medulla
DRG (dorsal respiratory group)
VRG (ventral respiratory group)
Pons also does play a role , DRG and VRG are by this
DRG controls (inspiration, expiration?) and VRG controls (inspiration, expiration)?
DRG: Inspiration
VRG: Inspiration, expiration
Define eupnea
Normal, rhythmic breathing
Define dyspnea
Difficulty breathing/respiratory distress
What nerve controls the diaphragm?
Phrenic nerve
Under normal tidal breathing, do many/any neurons fire during expiration?
No
Where are the central chemoreceptors
Ventrolateral surface of medulla oblongata
What do central chemoreceptors sense? HOW is it sensing this?
Changes in pH of CSF
Because of the blood brain barrier, hydrogen ions can’t really pass through. However CO2 is highly diffusible. It will cross the BBB and be converted to bicarb and hydrogen ions , and this is what is detected. Thus, they are detecting CO2 in blood indirectly by measuring pH locally
What do peripheral chemoreceptors respond to? What is the main component that responds to the gaseous elements?
Decreases in partial pressure of oxygen, pH, or increases in pCO2.
Glomus cells respond to ppCO2/O2 changes
What exactly are glomus cells?
Neuron-like cells in clusters that contain many potassium ion channels which respond to changes in gas content. THey then release neurotransmitters and signal to medulla/DRG
How much of chemoreception is done by periphery, vs central chemoreceptors?
It’s mostly central chemoreceptors (2/3), the other 1/3 is done by peripheral chemoreceptors
Purpose of pulmonary mechanoreceptors . Where are they located?
Prevent overinflation of the lungs (don’t allow for overstretching). They are located in the smooth muscle cells of airways (thus are very sensitive to mechanical changes locally in inspiration)
Hering Breur reflexes
Inflation: Inflation of lung inhibits inspiratory muscle activity via vagus nerve
Deflation: Deflation of lung initiates respiratory activity
Pulmonary irritant receptors – where are they, what do they respond to?
They are located between airway epithelial cells and can respond to a number of large stimuli (ex. cigarette smoke particles). They may play a role in asthma
J (juxtacapillary) receptors and bronchial C fibers - what are they, what do they respond to?
Respond to chemicals in pulmonary and bronchial circulation (J and C respectively). They are located in alveoli and conducting airways and are mechanically stimulated.
Nose/upper airway irritant receptors - how are they stimulated and what do tehy do?
Activated duringn diving, aspiration, sneeze refle, whenever something goes down the wrong pipe.
What is the prevailing theory as to why we yawn and sigh so much?
It rescues collapsed airways and alveoli by forcing more into that space. This forces them open.
THe action of air moving through also stimulates surfactant release.
Also: As you yawn or sigh, this mechanically breaks up cytoskeleton of SM cell and fluidizes it. As we get to higher generation of airways, SM is the dominant component that regulates the radii of systems. So if they squeeze down, they would hold airway at reduced radius
What’s going on when we cough or sneeze?
You create a massive expiratory force against a closed block (glottis). Then the pressure builds up - you have a massive gradient between lower and upper airways. This, followed by tracheal constriction via muscles and a transmural pressure difference leads to a VERY high velocity of flow of air out of the system
At any given CO2 level, ventilation is ___ due to peripheral chemoreceptors
Elevated, higher
At lower PaO2, ventilation at a given CO2 pressure is ____
Higher
Ventilation responses is more sensitive to O2, or CO2?
Co2
Slope of CO2 response curve can change in use of ____ , which is clinically important because of…?
Drugs, which is clinically important when you consider surgeries. – patients may not be properly maintaining ventilation rate themselves
What is a caveat to the “CO2 affects ventilation rate more than O2” rule
In patients with severe lung disease and chronic CO2 retention, hypoxic stimulus becomes the main stimulus for ventlation
Two types of sleep apnea
- Obstructive sleep apnea (tongue falls to base of throat, epiglottis falls, etc).
- Central sleep apnea (problem with CNS)
What is going on in obstructive sleep apnea
Something is physically obstructing the airway - pleural pressure is going in rhythimc motions, which eventually pulls on system hard enough to wake person up or pull things through system. But because of that block, this isn’t always happening.
What is going on in central sleep apnea
Due to a reduction of central feedback system (usually genetic) - loss of airflow, but this is because you’re just not getting the signal from you rbrain to breathe. Tends to only manifest at night.
Kussmaul breathing
deep breathing, normal frequency
apneustic breathing
Sustained periods of inspiration, quick expiration
cheyne-stokes breathing
Rapid hyperventilation followed by breaks
Biot’s respiration
Periods of kussmault breathing followed by rest
