Control of Lung Function Flashcards
What is the dorsal respiratory group the main location for?
Generation of the rate and rythm of breathing - Control of Inspiration
Where is the dorsal respiratory group located?
Dorsomedial medulla in the ventrolateral nucleus of the solitary tract
What is the ventral respiratory group responsible for?
Voluntary forced expiration control
Inhibition of the apneustic centre
Where is the ventral respiratory group located relative to the dorsal respiratory group?
Ventral to it
When is the ventral respiratory group inactive?
During quiet breathing
Where is the apneustic centre located?
Lower part of the pons
Where is the pneumotaxic centre located?
Upper part of the pons
What effect does the pneumotaxic centre have on the dorsal respiratory group?
Inhibitory
What effect does the apneustic centre have on the dorsal respitatory group?
Stimulatory
What effect does the dorsal respiratory group have on the ventral respiratory group?
Inhibitory
What effect does the ventral respiratory group have on the DRG and AC?
Inhibitory
Do action potentials at a low frequency stimulate the AC or the PC?
AC (apneustic)
When the action potentials fire at a higher frequency, are the AC or PC stimulated?
PC
What effect does the PC have on the action potentials and what is this effect followed by?
Causes a cessation (stop)
Follwed by a period of latency before the AC then stimulates the DRG again to increase the action potential frequency.
Which spinal nerves form the phrenic nerve?
C3, C4, C5
What motor and sensory innnervation does the phrenic nerve provide?
Motor innervation to the diaphragm
Sensation to the central tendon aspect of the diaphragm
What action do the external intercostal muscles contribute to?
Inspiration
What action do the internal intercostal muscles contribute to?
Expiration
If there are gaps in the capillaries of normal circulation, then why are they described as ‘continuous’?
Because these gaps between capillary endothelial cells are filled with H20.
What is the blood brain barrier and why is it important?
The purpose of the blood-brain barrier is to protect against circulating toxins or pathogens that could cause brain infections, while at the same time allowing vital nutrients to reach the brain.
Why is the blood brain barrier considered to have continuous capillaries?
Because they have tight junctions between capillary endothelial cells formed by nervous cells to prevent unnecessary leakage of molecules.
Can charged molecules pass the lipid bilayer?
Not without transporters
Is dissolved carbon dioxide able to pass through the lipid bilayer and therefore the blood brain barrier (BBB)?
Yes
How does this CO2 that is now in the CSF as it crossed the BBB from the capillaries, initiate activation of the DRG?
CO2 reacts with water to form a carbonate ion (HCO3-) and a proton.
Protons will enter the MO and interact with the afferent fibres.
These take the signal straight to the DRG to be able to determine what type of rate and rhythm should be created.
Where are irritant receptors found?
Embedded within and beneath airway epithelium (larynx, trachea, bronchi, and intrapulmonary airways)
What is the role of the irritant receptor?
Detects foreign mattter.
Leads to cough which involves forceful expiration against a closed glottis with sudden glottal opening and high velocity expulsion of air.
Where are pulmonary stretch receptors found?
Past the secondary bronchi
How are these stretch receptors activated?
Excessive inflation of lungs
What do the stretch receptors do once they are activated?
They send afferent signals to respiratory centres and stimulate pneumotaxic + VRG
Inhibit inspiration and stimulate expiration
Where are J-receptors found?
Alveolar walls in close proximity to the capillaries
What is the role of a J-receptor?
Respond to chemicals in pulmonary circulation, distention of the pulmonary capillary walls and accumulation of interstitial fluid (oedema).
Increases breathing frequency as a response to these factors - send APs via vagus nerve leading to bronchoconstriction and increased RR
What happens when you reach the CO2 threshold for breathing?
Accumulation of H+ beyond BBB activates the DRG - the struggle phase
What happens to the 3D structure of proteins if the level of acidity of the blood is not tightly regulated enough?
It is altered
Is a base anioic or cationic?
Anionic, also a molecule that reversibly binds to protons
Why does an acid have a low pH compared to a base?
It dissociates with H+, which creates a decreased pH as the higher the concentration of H+, the lower the pH.
Whereas a base binds to the H+ and would decrease the concentration.
What is the formula for calculating pH and what is the formula for then converting pH into H+ concn.?
-log10 [H+]
What is the difference between alkalaemia and alkalosis?
Alkalaemia - higher-than-normal blood pH,
Alkalosis - describes circumstances that will decrease [H+] and increase pH
What is meant by a ventilatory disturbance?
Minor change in breathing that changes pH which is then corrected by the kidneys which are slow responses.
What is meant by a metabolic disturbance?
Any non-lung cause of a change in the pH that is subsequently corrected for by the lungs which are fast responses.
What type of reaction is needed to correct an acidosis?
Alkolitic response
Where are the peripheral chemoreceptors found?
Bifurcation of carotid arteries in region called carotic and aortic bodies in the aortic arch.
Found very close to the baroreceptors.
What is the role of the peripheral chemoreceptors?
Stimulate breathing in response to hypoxia
Which part of the brain is responsible for the emotional responses?
Limbic system
How can the movement of a muscle lead to an increase in breathing?
Efferents from pirmary motor cortex to skeletal muscles partly innervate MO by sending volitional instructions to it as it will inevitably be necessary.
Proprioceptive afferents from muscle spindles and golgi tendon organs also innervate MO on way to brain.
Why is there a cold shock ventilator response?
Immersion in cold water (<10 degrees Celsius) causes a large and fast fall in skin temperature, detected by the superficial sensory nerve endings in the skin which evokes muscle spasms and hyperventilation.
