Lecture 22: Respiration 1 Flashcards
Why do you need to breath?
acquire oxygen and remove waste (CO2)
maintain blood pH
match metabolism
temperature regulation
What is the oxygen cascade?
ventilation -> pulmonary diffusion -> circulation -> tissue diffusion -> tissue metabolism
What are the three phases of respiration?
inspiration, post-inspiration and late expiration
What happens during inspiration?
diaphragm contracts and expands the thoracic cavity
abductor muscles of the upper airways contract resulting in dilation of the upper airways
subglottal pressure decreases
What happens during post-inspiration?
diaphragm starts to relax and volume of the thoracic cavity decreases
adductor muscles of the upper airways contract resulting in constriction of the upper airways
significant increase in subglottal pressure
What happens during late expiration?
diaphragm is relaxed and volume of the thoracic cavity is compressed
muscles of the upper airways are relaxed and the upper airways are opened up a little bit more
subglottal pressure is decreased
What does the phrenic nerve innervate?
the diaphragm
What does the hypoglossal nerve innervate?
the genioglossus muscle
What does activity of the recurrent laryngeal nerve lead to during inspiration?
contraction of the abductor muscles of the upper airway to reduce resistance and increase airflow
Where is the ventral respiratory group located?
in the medulla
What do brainstem regions produce synchronised respiratory output to?
the spinal cord
What is pre-BötC sufficient for?
generating respiratory rhythm
What would happen if you destroyed pre-BötC neurons?
this would lead to a decrease in respiratory frequency and amplitude of motor output
What is the function of pre-BötC neurons?
pre-inspiratory or early inspiratory function
little to no expiratory function
What do pre-BötC neurons express?
NK1-receptor, somatostatin(SST) and Dbx-1 transcription factor
What type of neuron are pre-BötC neurons?
glutamatergic
there is a subset that is glycinergic
What is the endogenous ligand for the NK1-receptor?
substance P
Why type of receptor is NK1?
G-protein coupled receptor which is internalised following stimulation by substance P
attached ligand is also internalised
What is saporin?
a ribosomal inactivating protein (RIP) which inhibits protein synthesis and initiates cell death
What is required for saporin to enter the cell?
needs to be bound to a chaperone
Are NK1-R expressing cells in pre-BötC actually required for normal breathing rhythm generation?
yes
What did destruction of NK1-receptor expressing neurons in the pre-Botzinger complex result in?
irregular breathing with large periods of apnea
What did silencing of the pre-Botzinger complex by the insect peptide allatostatin after transfection with AAV result in?
cessation of breathing
What do experiments in destruction and silencing of pre-Botzinger complex neurons serve to demonstrate?
pre-Botzinger complex is essential and necessary for respiratory rhythm generation
What are the properties of pre-Botzinger neurons?
action potentials continue to fire even when all synaptic transmission is inhibited
What allows for intrinsic bursting in pre-Botzinger neurons?
persistent sodium current
What are two important factors in generation of bursts in pre-BötC neurons?
Ca2+ activated nonselective cationic current AND persistent sodium currents
How does intra-alveolar pressure and intra-pleural pressure change during inspiration?
intra-alveolar pressure decreases then increases
intra-pleural pressure decreases
How does intra-alveolar pressure and intra-pleural pressure change during post-inspiration?
intra-alveolar pressure increases then slightly decreases
intra-pleural pressure increases
How does intra-alveolar pressure and intra-pleural pressure change during late expiration?
intra-alveolar pressure decreases
intra-pleural pressure increases
How does airflow change during respiration?
inspiration: air flow in
post-inspiration: air flow out
late expiration: air flow out
