Semester 2; L4 - The control of respiration Flashcards
what are the three examples of patterns of forced expiration?
Normal
Obstructive
Restrictive
what parts of the brain are responsible for respiratory system?
sphenoidal air sinus
pituitary body
pons
medulla oblogata
what is the main function of central and peripheral chemoreceptors?
regulate respiratory activity
Where are central chemoreceptors located?
in the medulla
what can central chemoreceptors maintain?
pH
arterial blood pO2, pCO2
Can a change in pH alone stimulate central chemoreceptors?
no
Where are peripheral receptors located?
cardiac and aortic bodies
What are the functions of peripheral receptors?
response to changes in blood molecule concentrations
helps to maintain cardiorespiratory homeostasis
What stimulates the peripheral chemoreceptors?
The firing will be stimulated by a reduction in PaO2
The reduction may be caused by lack of pH or increase of CO2
What does the firing of those neurones from peripheral chemoreceptors result in?
Stimulates medullary respiratory neurones
Increased firing of motor neurones to respiratory muscles (principally diaphragm and ext. intercostals)
Increased ventilation
What stimulates the central chemoreceptors?
an increase in PaCO2, csf PaO2, and a reduction of pH stimulates firing of neurones
What does the firing of those neurones from central chemoreceptors result in?
Stimulates medullary respiratory neurones
Increased firing of motor neurones to respiratory muscles (principally diaphragm and ext. intercostals)
Increased ventilation
What is oxyhemoglobin dissociation curve?
relates oxygen saturation (SO2) and partial pressure of oxygen in the blood (PO2)
What is oxyhemoglobin dissociation curve determined by?
hemoglobin’s affinity for oxygen
What is hemoglobin’s affinity for oxygen?
how readily hemoglobin acquires and releases oxygen molecules from its surrounding tissue
What is hypercapnia?
A condition of abnormally elevated carbon dioxide (CO2) levels in the blood
How does hypercapnia stimulate the central chemoreceptors?
This is due to CO2s ability to easily diffuse across the blood-brain barrier
The build up of CO2 in the csf, stimulates the central chemoreceptors to fire
Why is pH buffering lower in CSF than in blood?
Due to much lower protein content
what is hypoxia?
the oxygen pressure in the blood going to the tissues is too low to saturate the hemoglobin
In the carotid body, what do the Peripheral chemoreceptors react when hypoxia occurs?
They release neurotransmitters onto the carotid sinus nerve, which branches on to the glossopharyngeal nerve
The glossopharyngeal nerve connects to the brain stem, in which alerts the respiratory centres.
What are the pontine respiratory group (PRG) important for?
Important in regulating inspiration time
Damage here causes long inspiration time
What are the Dorsal respiratory group (DRG) important for?
Primarily inspiratory, connect to contralateral phrenic nerve motor neurones
What are the ventral respiratory group (VRG) important for?
Both inspiratory and expiratory, connect to respiratory motor neurones or to DRG
what does the central respiratory rhythm generator consist of?
Dorsal Respiratory Neurons and Ventral Respiratory Neurons
when one is active, the other is dormant
What does the central respiratory rhythm generator stimulate?
lower respiratory neurones, which in turn stimulate phrenic and intercostal nerves
Which eventually stimulate the respiratory muscles
What pattern does inspiration incur on a graph?
a ramp,
activity intensifies, however when expiration occurs the activity stops.
Why is it harder to breathe at a high altitude?
the atmospheric pressure is much less
And the total O2 content in the atmosphere is reduced at higher levels
What happens to the body at a high altitude?
Driven by low alveolar PO2 (NB: at low total barometric pressure, PO2 is still ~20%)
↑Ventilation allows the body to expel more CO2
This causes CSF pH to rise (initially)
As HCO3 is transported out of CSF pH falls
Stimulates ventilation (in addition to hypoxic drive)
