Control of Ventilation NU 490 MIDTERM
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What three groups are involved in the control of ventilation?
1. Dorsal Respiratory Group: inspiration, most fundamental role in control of respiration
2. Ventral Respiratory Group: inspiration and expiration, works simply as an overdrive mechanism
3. Pneumotaxis Center: decreases duration o finspiration, inhibits the dorsal group neurons
Where is the dorsal respiratory group located?
What two ways does the dorsal respiratory group act on the inspiratory "ramp" signal?
1. controls the rate of increase
2. limiting point where the ramp ceases
True or False: Dorsal Respiratory Group is active in normal, quiet breathing.
Which is the ventral respiratory group more closely associated with: inspiration or expiration?
True or False. Ventral Respiratory Group is active during normal, quiet breathing.
- The ventral respiratory group is inactive during normal, quiet breathing. The VRG becomes active when the respiratory rate increase (ie exercising) and contributes to inhalation and exhalation.
What effect does the pneumotaxic center have on inspiration?
Decreases the duration of inspiration by inhibiting dorsal group neurons
What effect on respiratory rate would a strong pneumotaxic center have?
Respiratory rate would be increased...
conversely, in a patient with a weak pneumotaxic center, respiratory rate would be decreased.
Tell me about the apneustic center.
Not fully understood, but we know it isnt present in normal respiration.
In abnormal circumstances: prolongs ramp up (AKA cheynes stokes)
Duration of inspiration is controlled by what two groups?
- 1. dorsal group
- 2. pneumotaxic group
What three places transmit signals to the dorsal group?
What two pathways do they use?
- 1. peripheral chemoreceptors
- 2. baroreceptors
- 3. lung receptors
- These three receptors use two pathways to reach the dorsal group:
- 1. glossopharyngeal nerve
- 2. vagal nerve
How do lung inflation signals benefit the lung?
They are a protective mechanism of the lung: only come into play in overinhalation- lung stretch receptors send signals through the vagal nerves to the dorsal group to switch off the ramp [AKA the HERING-BREUER REFLEX]
Tell me how CO2 affects the respiratory center.
Under normal conditions, CO2 is the main controller of respiration.. NOT O2!
-as PCO2 increases, alveolar ventilation increases (not a direct relationship, but definitely profound)
Which of these two things DIRECTLY affects the respiratory center? Tell me how it does this.
H+ or CO2
-Crosses the blood brain barrier as H2CO3 and then H+ is end product that directly affects respiratory center
The stimulatory effect of increased CO2 in the respiratory center decreases after... [amount of time]
Where are peripheral chemoreceptors located?
- 1. aortic bodies
- 2. carotid bodies
True or False: Peripheral chemoreceptors are active in normal respiration.
Peripheral chemoreceptors are inactive in normal respiration, and are only activated in instances of hypoxia.
Aortic bodies, a peripheral chemoreceptor, are primarily found in:
The aortic arch
Carotid bodies, a peripheral chemoreceptor, are mainly located:
in the carotid!! ;)
Between carotid and aortic bodies, which detect changes in O2 first?
What PO2 level (and below) activates peripheral chemoreceptors?
Some patients depend on peripheral chemorecepors for their hypoxic drive to breath, in these patients it would be especially important to monitor respiratory following what type of surgery? (for example)
A bilateral carotid resection
True or False: Effects on the Respiratory Center of Additive!
For example, if PO2 is low (40) and pH is low (7.3) the two together will create an even GREATER INCREASE in alveolar ventilation
True or False: Voluntary control of respiration is controlled through the cortex.
What effect does irritant receptors have on the airway?
Irritant receptors in the trachea, bronchi, and bronchioles cause coughing and bronchial constriction
What effect do "J" Receptors have on the respiration?
"J":Juxta-receptors located in the pulmonary capillaries: when the pulm. capillaries are engorged they create the sensation of dyspnea
What effect does brain edema have on respiration?
CNS is depressed, respiration can be inactivated by edema of brain
True or False: With any volatile anesthetic, the respiration rate becomes faster and shallow breathing occurs
During anesthesia, _________ oxygenation is impaired whether in spontaneous or controlled breathing.
In deep anesthesia, what paradoxical movement can occur?
Paradoxical movement of the diaphragm... diaphragm can descend but intercostal muscles won't widen (this can also happen if a patient is partially paralyzed)
When a patient is supine, the FRC is ________.
When a patient is under anesthesia, the FRC is decreased for a number of reasons... tell me them.
- 1. pt is most likely supine, which decreases FRC
- 2. under anesthesia, FRC is decreases due to relaxed diaphragm and easily transmitted upward abdominal pressure
Patients are _________ sensitive to increased levels of PCO2 under anesthesia.
Patients are less sensitive to increased level of PCO2, at any given PCO2 the deeper the anesthetic, the lower the alveolar ventilation will be...
Heart failure (longer for improperly oxygenated blood to reach the brain) and brain edema (dorsal group dysfunction) are both probably causes of what type of abnormal pattern of breathing?
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