CVR 4: Respiratory Flashcards
What two areas of the brain not in the medulla oblongata are involved in the control of breathing?
Pneumotaxic and apneustic centres in the pons.
How many different areas of the brain are involved in controlling breathing?
Four
What areas of the brain not in the pons are involved in the control of breathing?
Dorsal respiratory group and ventral respiratory group, both in the medulla oblongata.
Which area of the medulla oblongata is predominantly active during inspiration?
The dorsal respiratory group (DRG).
What is the central pattern generator?
A neural network in the dorsal and ventral respiratory groups in the medulla oblongata, provides background ventilatory drive.
Concentration of which gas predominantly influences breathing?
CO2
Where are the central chemoreceptors and what do they monitor in regards to breathing?
In the brainstem.
CO2 passes across blood/brain barrier, leading to increase in hydrogen ions in CSF (bicarbonate buffer system).
Hydrogen ion concentration is monitored by chemoreceptors in the brainstem.
Where are the peripheral chemoreceptors for respiration and what do they measure?
Carotid bodies and aortic arch.
Measure PaCO2 predominantly, but also measure PaO2 and pH.
If PaO2 decreases, what happens to minute ventilation?
Increases.
In hypoxia, does a given PaCO2 level trigger higher or lower minute ventilation?
Higher.
What are the three types of mechanoreceptors in the lungs that send afferent information to the respiratory control centres via the vagus nerve?
Stretch, irritant, and J receptors (juxtapulmonary capillary)
Where are the receptors, activated by swallowing, which prevent respiratory activity during swallowing?
The pharynx.
Why can x-rays be dangerous?
They are a form of ionising radiation, which can damage tissue, cells, and DNA (mutagen).
What colour are more dense structures on an x-ray? Give an example.
White. E.g. bones.
On a chest x-ray, why is the diaphragm higher on the right?
Due to the presence of the liver.
What anatomical landmark on a chest x-ray can be used to assess symmetry?
The clavicles.
Why aren’t the anterior aspects of the ribs easily visible on a chest x-ray?
They are cartilaginous.
Which view is most ideal for a chest x-ray and why; AP (anterior-posterior) or PA (posterior-anterior)?
PA (posterior-anterior); patient facing the detector, standing up.
This is because there will be a crisper image and accurate size of the heart than in AP view, and the scapulae can be protracted.
Which causes more ionising radiation for a patient, chest x-ray or abdominal x-ray?
Abdominal x-ray.
Where should you look to check for cyanosis?
Under the tongue at glossal artery.
What is the difference between Type 1 and Type 2 respiratory failure?
Both = hypoxaemia (low PaO2)
Type 1 = hypocapnia/normal PaCO2
Type 2 = hypercapnia (high PaCO2)
What causes Type 1 respiratory failure?
Many different causes, including infectious, congenital, and neoplasmic causes.
What causes Type 2 respiratory failure?
Lack of respiratory drive, excess workload, and bellows failure. Under-ventilation leading to hypercapnia. For example, in COPD.
Why might someone with anaemia not be cyanotic when severely hypoxic?
Cyanosis is caused by large amount of deoxygenated haemoglobin. Anaemic patient might not have enough haemoglobin to be cyanotic.
Why might it be dangerous to give too much oxygen to a patient with COPD?
In chronic hypercapnia, such as in COPD, chemoreceptors thought to reset. Breathing is no longer driven by increase in PaCO2 and instead driven by decrease in PaO2.
If give supplementary O2 and raise PaO2, the patient might lose their ventilatory drive and hypoventilate.
What is respiratory failure?
Failure of gas exchange; inability to maintain normal blood gases.
At the level of what rib is the optimal VQ ratio seen?
Rib 3
What does PaCO2 depend on?
A constant (K), the production of CO2 (VCO2), and alveolar ventilation (VA).
PaCO2 = K x VCO2 / VA
The total lung capacity is found by adding what two lung volumes?
Residual volume and vital capacity.
What are the four stages of lung development?
Embryonic
Pseudoglandular
Cannalicular
Alveolar
When is the alveolar stage of lung development?
At 25 weeks until term.
Which stage of lung development occurs at 16-25 weeks?
Cannalicular
When is the pseudoglandular stage of lung development?
5-17 weeks
By what week in lung development do the lung buds enlarge to form right and left main bronchi?
5th week
What happens during the pseudoglandular stage of lung development?
Different cells/structures start to develop e.g. mucous glands.
Angiogenesis; however, pulmonary vessels will be constricted due to hypoxic environment (lungs full of fluid).
In lung development, when do the respiratory bronchioles and alveolar ducts develop?
16-25 weeks (Cannalicular stage)
In what stage of lung development do the alveolar sacs and type 1/2 pneumocytes develop?
Alveolar stage, 25 weeks until term.
When do the lungs finish developing?
3-5 years old.
Why is pulmonary vasoconstriction important in the foetus?
Oxygenated blood comes from the placenta into right side of the heart.
Pulmonary vasoconstriction increases pressure in right side of the heart, so blood preferentially flows through foramen ovale. Any remaining flows through ductus arteriosus.
What two vessels are joined by the ductus venosus? What organ does this cause a proportion of blood to bypass?
The umbilical vein and the inferior vena cava. Bypassing the liver.
Which carries oxygenated blood from the placenta to the foetus, the umbilical artery or the umbilical vein?
The umbilical vein.
How does the ductus arteriosus close after birth?
The muscular wall contracts, mediated by bradykinin.
How is the foramen ovale closed after birth?
In the first breath, lungs are oxygenated which causes pulmonary vessels to dilate. This drops the pressure in the right side of the heart. Foramen ovale closes as pressure in left side of the heart becomes higher than the right.
In Laplace’s law, what is the pressure in a sphere (e.g. alveoli) proportional to?
Surface tension and radius.
