Case 5 Flashcards
Fill in the boxes for the size of particles associated with each part of the respiratory tract.
Upper: 2.5 - 10um
Lower: 0.1 - 2.5um
Distal: <0.1um
Where are the two respiratory rhythm generators found?
One in the pre-Boetzinger complex.
One in the retrotrapezoid nucleus / parafacial respiratory group.
What is the pre-Bötzinger complex? Where is it found?
Found in the Ventral Respiratory Group (VRG) on the venterolateral surface of the medulla.
It initiates spontaneous breathing.
What four cell groups make up the Ventral Respiratory Group (VRG)?
nucleus retrofacialis
nucleus retroambiguus
nucleus para-ambiguus
pre-Bötzinger complex.
What type of neurones deoes the Ventral Respiratory Group (VRG) contain? What is its function?
It contains inspiratory and expiratory neurons.
The VRG is secondarily responsible for initiation of inspiratory activity (dorsal group is mainly responsible).
Where is the dorsal respiratory group (DRG) located? What is its function?
Located in the dorsomedial region of the medulla. Primarily responsible for the generation of inspiration - only contains inspiratory neurones.
What is the DRG stimulated via?
It is stimulated via the apneustic center in the lower pons.
This is responsible for modifying responses to sensory information received from chemoreceptors and mechanoreceptors.
What is the DRG inhibited by?
Pneumotaxic center.
What is the function of the Pneumotaxic center (aka. pontine respiratory group (PRG))?
It antagonizes the apneustic center –> inhibits inspiration.
The PRG limits the action potentials in the phrenic nerve, decreasing the respiratory rate.
What happens when neurons DRG fire? (include phrenic nerve, diaphragm etc)
Impulses travel down the phrenic and intercostal nerves.
This stimulates the diaphragm and external intercostal muscles to contract.
Volume of the thorax expands and air moves into the lungs due to the negative pressure, producing inspiration.
What happens when neurons in the DRG stop firing?
Inspiratory muscles and diaphgram relax.
Inspiration stops –> expiration begins.
Which box represents
Restrictive lung disease?
Obstructive lung disease?
What would the ratio of V/Q be for each?
Restrictive –> Lowered FEV1 and FVC.
Ratio: >0.7
Obstructive –> Lowered FEV1, FVC normal/reduced.
Ratio: <0.7
What areas are represented in the green boxes?
(Hint: located in the pons - recieve information from higher centres e.g. cerebral hemispheres, hypothalamus)
What areas are represented in the blue boxes?
(Hint: found in the medulla)
Green - apneustic and pneumotaxic areas.
Blue - expiratory and inspiratory centres.
(DRG and VRG)
What is equation for calculating a pack year?
Number of pack-years =
(packs smoked per day) × (years as a smoker)
OR:
(number of cigs smoked / 20) x (years as a smoker)
e.g. 1 pack-year =
smoking 20 cigarettes (1 pack) x 1 year
Calculate the pack year for a person who has smoked 15 cigarettes a day for 40 years.
15 cigarettes = 3/4 pack.
Pack years = 0.75 x 40 = 30 pack years.
Calculate the pack year for a person who has smoked 10 cigarettes a day for 6 years.
10 cigarettes = 1/2 pack.
Pack years = 0.5 x 6 = 3 pack years.
Calculate the pack year for a person who has smoked 40 cigarettes daily for 20 years.
40 cigarettes = 2 packs a day.
Pack years = 2 x 20 = 40 pack years.
Would the V:Q ratio be low or high for somebody with asthma?
Compensation?
Low V:Q ratio across the whole lung.
Pulmonary vasoconstriction to reduce perfusion to areas that are poorly ventilated.
In conditions such as COPD. this can lead to cor pulmonale.
An area with perfusion but no ventilation is termed a ___? Ratio?
SHUNT
V:Q ratio is zero.
An area with ventilation but no perfusion is termed ____?
ratio?
DEAD SPACE
V:Q ratio = infinity
Explain how ventilation differs from the apex to the base of the lung in this diagram.
BASE:
Less negative IP pressure - alveolar volume is reduced. Alveoli are more compliant. Perf > Vent
APEX:
More negative IP pressure - alveolar volume is increased. Alveoli are less compliant. Vent > Perf
Explain how perfusion differs from the apex to the base of the lung in this diagram.
BASE:
Perf > Vent. Alevolar volume is reduced due to the less negative IP pressure and gravity acting so blood flow is continuous (capillaries are not compressed).
APEX:
Vent > Perf. Alveolar volume is greater due to the more negative IP pressure. Blood vessels are compressed.
Why shouldn’t patients with allergic asthma not take NSAIDs?
NSAIDs inhbit COX so they direct arachidonic acid to the lipoxygenase pathway causing more leukotrienes to be made.
They are similar to histamine but are produced later on in the reaction.
They cause inflammation, smooth muscle contraction and seretion of mucus.
These responses could be dangerous during an allergic asthma attack if an individual was taking NSAIDs.
What is the function of the nasal cavity and sinuses?
What is the function of the nasal conchae?
Slows air entering the body.
The nasal cavity is narrow compared to the sinuses, therefore the air is slowed down giving foreign particles a chance to fall out and be trapped (by nasal hair)
Bones called nasal conchae project into the nasal cavity and form a series of folds called turbinates which increase the surface area of the nasal cavity making it more effective at heat exchange.
Which part of the respiratory tract has the highest resistance?
Trachea / Main Bronchi
Surface area is indirectly proportional to resistance
(ssurface area increases from trachea -> alveoli)
However resistance is also directly proportional to the length of the tube.
e.g. bronchioles are short tubes = little resistance = greater surface area compared to trachea.
What is the action of Theophyllines?
What is the problem with using them?
*similar to caffeine*
They are phosphodiesterase inhibitors (act through Gs - inhibits MLCK) = increased cAMP = more PKA.
Actions: [1] Smooth muscle relaxation
[2] anti-inflammatory: inhibits TNF-a and leukotriene production –> less inflammation / smooth muscle
Hepatic enzyme activity varies between patients so varying levels released into blood.
What is meant by ‘biographical disruption’?
A destabilisation, questioning and reorganisation of identity after the onset of chronic illness.
