Control of Respiration Flashcards
What are the central chemoreceptors?
Located inside the brainstem, on the other side of the BBB
Sensitive to fluctuation of CO2
What are the peripheral chemoreceptors?
Located in the neck
Respond to Arterial [H+], Arterial PCO2, Arterial PO2
What is the principle controller of ventilation?
PaCO2 through central chemoreceptors
Increases respiratory drive when activated
How does a change in PaCO2 activate the central chemoreceptors?
CO2 readily crosses the BBB and enters the CSF
In the CSF, undergoes conversion to H2CO3, then readily dissociates to H+ and bicarbonate
The increase in H+ activates the chemoreceptors, however they are also sensitive to very small increases in CO2
What occurs in response to the activation of the central chemoreceptors?
Ventilation increases
The increase in ventilation causes PaCO2 to fall, and in turn, a rise in CSF pH back to normal. Central Chemoreceptors decrease firing, and ventilation goes back to normal
Where are the peripheral chemoreceptors located and what do they respond to?
Carotid and aortic bodies
Both respond to changes in [H+]
Only the carotid bodies respond to low PO2
Describe the shift in main respiratory drive during hypoxia.
In the case of hypoxia, if the PO2 falls below 60mmHg, the main respiratory drive shifts from PCO2 to fluctuation in PO2.
The effect of PCO2 still exists, its just the main drive is shifted to PO2
Response to hypoxia never adapts
What is the most powerful stimulus on respiratory drive?
Concentration of hydrogen ions (pH) in arterial blood
Elevation of respiration in response to increase in arterial pH is mediated solely by peripheral chemoreceptors
How do the responses to hypoxia and hypercapnia affect each other?
Hypercapnia or acidosis amplify the effects of hypoxia
The increase in ventilation to hypoxia is greater in the case of hypercapnia than when the PCO2 is normal
What is the danger of treating a lung disease patient with ventilation?
Patient with a low V/Q mismatch will lead to hypoxemia and hypercapnia
Acidosis will be compensated for through renal compensatory mechanisms, meaning patient is only relying on hypoxic drive for ventilation
Giving oxygen can reduce this drive and cause depressing ventilation, must be monitored closely
What is the role of the phrenic nerve in inspiration?
Innervates the diaphragm, exits from C3-C5
What nerves control the accessory muscles for respiration?
Internal intercostals - thoacic nerves
Abdominal muscles - lumbar nerves
Trauma that results in damage to these regions can have major impacts on respiration
What does the respiratory control center consist of?
Dorsal respiratory groups
Ventral respiratory groups
Located in the medulla
What is the role of the dorsal respiratory groups in respiration?
Consists chiefly of inspiratory neurons that control the diaphragm and intercostals
Receives input from peripheral and central chemoreceptors, stretch receptors and higher brain centers
Responsible for the basic rhythm of breathing, triggers inspiration at a rate of 12-15 breaths/minute
What is the role of the ventral respiratory groups in respiration?
Contains both inspiratory and expiratory neurons
Controls the constituent muscles of the upper airways that regulate the diameter of the upper airways during breathing
Also controls the muscles of exhalation and accessory muscles of inspiration
What is the Apneustic Center?
Located in the Pons, continually sends neural impulses to stimulate inspiratory neurons of DRG and VRG
What is Apneustic Breathing?
Respiratory cycle holds in inspiration which is periodically interrupted by expiration
Results from cutting the pons, removing the pneumotaxic center and vagus nerve
Where is the pneumotaxic center and what are its major functions?
Located in the Pns
Prevent aneupsis
Enhance and fine-tune the rhythmicity of breathing
What is congenital central hypoventilation syndrome (CCHS)?
Central pattern generator is inoperative due to the insensitivity of chemoreceptors to CO2, O2, and pH
Automatic breathing is lost, Voluntary breathing is intact
Danger is sleep and loss of consciousness
Treated with a permanent tracheostomy that is connected to a ventilator during sleep
What conditions alter respiratory control in the medulla?
Cerebral edema
Intracerebral Abnormality
Acute Poliomyelitis
CNS depressants and stimulants
What is the difference between the effect of mild and severe hypothermia on respiration?
Mild increases ventilation due to sympathetic nervous system as the body works to preserve heat
Severe hypothermia depresses ventilation as a result of general of neural activity
What is Cheyne-Stokes breathing?
10-30 seconds of apnea followed by gradual increase in volume and frequency of breathing until another period of apnea occurs
What is Biot’s respiration?
Characterized by rhythmic but deep respiration movements which alternate with long respiratory pauses
Occurs in meningitis patients and disorders of cerebral circulation
Also associated trauma and opioid use
What is obstructive sleep apnea?
Upper airway is obstructed because there is too much fat around the pharynx
Severity measured by the Apnea/Hypopnea index
What is central sleep apnea?
Characterized by a normal deep inspiratory cycle interchanged with complete cessation of breathing
Typically a problem with control of respiration
Different from Cheyne-Stokes because there is no hyperventilation and waning of ventilation
What is Kussmaul’s respiration?
Hyperventilation, gasping, deep and labored respiration
Usually seen in DKA, kidney failure, or other states characterized by a high degree of acidosis
