Pulmonary Physiology: Control of Respiration Flashcards
Transection of the spinal cord above the origin of the _________ nerves at C1 stops breathing.
phrenic nerves
Where are the centers for autonomic control of breathing located? Where are the centers for voluntary control located?
Autonomic centers are in the medulla.
Voluntary control originates in the cerebral cortex.
What is eupnea?
Normal breathing
What is hyperpnea?
Increased rate AND depth
What is Cheyne-Stokes respiration?
Abnormal breathing characterized by tidal volume fluctuation and periodic apnea. Indicative of a severe CNS disorder.
What is Kussmaul breathing?
Regular rapid rate with large tidal volume due to metabolic acidosis.
What is ataxic breathing?
Highly irregular inspirations usually separated by long periods of apnea. Seen with lesions in the medulla.
What is apneusis?
Prolonged inspirations separated by brief expirations.
What are the two groups of nerves called located in the medulla that are responsible for autonomic control of breathing?
Dorsal respiratory group (DRG) and ventral respiratory group (VRG)
Afferent signals come into the DRG in the medulla via the ______ and ________ nerves.
vagus and glossopharyngeal nerves
Have experiments shown that the pons can be severed from the medulla while still preserving basic breathing patterns?
Yeah
Describe how action potentials from the DRG affect breathing.
The DRG generates a RAMP SIGNAL (APs that progressively increase in frequency over ~3 seconds), which initiates inspiration. The ramp signal stimulates phrenic nerve activity, which sends APs to the diaphragm for contraction and inspiration. The APs suddenly stop for ~3 seconds, allowing for exhalation.
What two major connections does the DRG make with other nerves?
- Phrenic nerve –> diaphragm
2. Spinal nerves –> EXTERNAL intercostals and scalenes (that contract for inspiration)
What connections does the VRG make with other nerves?
VRG makes connections with phrenic nerve and spinal nerves also but this is poorly understood.
It also sends out motor neurons to upper respiratory muscles (larynx, pharynx, mouth, nostrils, etc.) that activate during heavy breathing.
From which respiratory group (DRG or VRG) does expiratory output come from?
VRG exclusively. It stimulates INTERNAL intercostals and abdominal muscles for expiration.
What is the Botzinger complex?
A section in the upper part of the VRG that may act as a respiratory rhythm generator, containing pacemaker cells that are thought to excite the DRG to make ramp signals.
What is the apneustic center and what does it do?
It is located in the lower pons and may exhibit an excitatory effect on the DRG and VRG and prolong ramp potentials.
What is the pneumotaxic center and what does it do?
It is located in the upper pons and it switches off inspiration when activated.
What are the two main peripheral structures/things that respond to PaO2, PaCO2, and arterial pH?
The aortic and carotid bodies.
How do the aortic and carotid bodies work?
Located in the aortic arch and carotid bifurcation, they contain Type 1 Glomus cells (specialized nerve cells that send APs in response to low PaO2, low pH, or high PaCO2) that travel to the DRG via cranial nerves IX (glossopharyngeal) and X (vagus) to increase ventilation.
Which of the two peripheral chemoreceptors (aortic bodies or carotid bodies) are more sensitive to hypoxia?
The carotid bodies are more sensitive to hypoxia
Why is the DRG response to increase ventilation much more sensitive to increased PaCO2 than to low PaO2?
The body is more resistant to low PaO2 levels because Hb has a reserve O2 storage that doesn’t run out until PaO2 levels get quite low.
Is there a stronger increase in ventilation by the DRG if PaCO2 is high concomitantly with low PaO2 levels?
Yeah
How do central (CNS) chemoreceptors work when H+ ions don’t cross the blood-brain barrier?
CO2 can cross the BB barrier, which then combines with H2O to make H2CO3 –> H+ + HCO3-. The increase in H+ in the CSF (lower pH) triggers the receptors, which provide input to the DRG.
