022 Control of ventilation Flashcards
How is respiration controlled in medulla and pons? What about higher parts of the brain?
Medulla is responsible for regulation of involuntary response of breathing. Pons is more responsible for the fine-tuning of the rate and rhythm.
Where are the central chemoreceptors located in the brain?
Central chemoreceptors are located in the extracellular fluid of the brain.
How does the blood brain barrier work?
The blood vessels within the brain are extremely impermeable to charged molecules. Therefore, only CO2 is able to move in and out of the vessel into the CSF. This gives a direct correlation between concentration of CO2 in the blood and in the CSF, which can then be detected by chemoreceptors.
What are some causes of the decrease in ventilation rate?
Sleep, respiratory depressants, and extremely high PA CO2 values.
What happens during a head trauma?
During a head trauma, brain will be crushed through the foramen magnum (opening that the medulla and pons lie on top of). This puts huge pressure on the brainstem, and coning may occur (patient dies). If you cut spinal cord at C2, you immediately disrupt sensation to lungs.
What are the different types of receptors that regulate breathing?
Chemoreceptors, peripheral receptors, juxtapulmonary receptors, pulmonary stretch receptors, joint and muscle proprioceptors, pain receptors, thermoreceptors, airway/irritant receptors.
Do central or periphery receptors have equal effect?
Central receptors are much more important in regulating ventilation as it detects CO2 levels. We are much more sensitive to the PACO2 rather than PAO2. Our periphery receptors detect PAO2.
Where are the peripheral chemoreceptors located?
Located in the carotid body, and aortic arch body.
When pH in the CSF decreases drastically, how is it balanced out?
When [H+] reaches a certain concentration in the CSF and chemoreceptors cannot increase ventilation enough to exclude the [CO2], ion channels in the blood will open HCO3- channels. This allows bicarbonate to move into the CSF and normalize the pH, usually occurring after hours.
Why do we have to be careful when giving patients with chronic lung disease oxygen?
Patients with chronic lung disease causes long term central chemoreceptor insensitivity to CO2. Instead, they begin to rely more on hypoxia drive by peripheral receptors. By giving too much oxygen, then you will suppress their ventilation even more. These groups of patients must be given controlled oxygen therapy.
How much can ventilation increase by during exercise and what is the limiting factor?
It can increase 20x and the limiting factor is cardiac output.
What is the relationship between PaO2 and ventilation rate? What about PaCO2?
PAO2 and ventilation rate relationship is exponential. The ventilation does not increase that significantly unless PAO2 drops to about 50mmhG e.g. in high altitudes. This is because it would be a waste of work to increase ventilation with slight drops in PAO2 as the haemoglobin bound to oxygen are all saturated, and decreasing PAO2 does not affect the saturation of haemoglobin as significantly. PA CO2 and ventilation have a linear proportional relationship. With an increase in 1mmHg in pCO2, ventilation will increase by 2-3L/min.
How do pulmonary stretch receptors contribute to ventilation?
Pulmonary stretch receptors are located on the smooth muscles of the lung. When lung inflates, it signals the stretch receptors to reduce ventilation rate. E.g. hyper inflammatory lungs signal for shorter, slower respiration rate.
How do J receptors work?
J receptors are juxtacapillary – they respond to pulmonary vascular congestion by increasing respiratory rate. It is partly responsible for the hyperventilation during heart failure.
Are central chemoreceptors responsible for increased ventilation during exercise? And why?
No, venous PA CO2 increases during exercise but PA CO2 does not. This means that chemoreceptors are not responsible in increasing ventilation. Instead
