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Flashcards in Respiratory System 6 Deck (22)
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What is alveolar volume?

The difference between the tidal volume and the dead space volume


What is the rate at which alveolar volume is ventilated proportional to?

The alveolar volume and to the frequency of breathing- hence units are consistent


What are the consequences of hyperventilation?

1. Accumulation of O2 in the alveoli (increase of PaO2 and PAO2)
2. Decrease of CO2 in the alveoli (decrease of PACO2 and PaCO2, increase of arterial pH; respiratory alkalosis- eventually alkalotic coma)


Consequences of Hypoventilation?

1. Diminution of O2 in the alveoli (decrease of PAO2 and PaO2)
2. Accumulation of CO2 in the alveoli
(Increase of PACO2 and PaCO2, decrease of arterial pH; respiratory acidosis, eventually, acidotic coma)


What is anoxia?

Absence of oxygen


What did the men who increased their ventilation most in response to low O2 have?

Highest arterial O2


What does breathing rely on?

Neural input to the muscles of ventilation


Where does respiratory rhythm originate?

In the brainstem


What generates the basic respiratory rhythm?

Two groups of neurons in the medulla oblongata


What are the medullary centres?

Dorsal respiratory group (DRG; neurons of which are active primarily during inspiration), and Ventral respiratory group (VRG, some neurons of which are active during inspiration, others during expiration and some during the transition)


Where is the rhythmic drive originated in the brainstem transmitted to?

Motoneurons in the brainstem (cranial motoneurons) and spinal cord which, in turn,drive Ye muscles involved in breathing (diaphragm, intercostals, upper airway muscles)


Where are slowly adapting stretch receptors located?

In the walls of the bronchi and bronchioles


What do slowly adapted stretch receptors do?

Send signals, via myelinated fibres in the vagus nerve, to brainstem respiratory centres; activation of these receptors by lung inflation terminates inspiration


What are irritant receptors?

Sensors in the airways that send signals via myelinated and unmyelinated (C-fibres) in the vagus nerves


What do irritant receptors respond to?

Noxious mechanical and chemical stimuli (smoke, smog, pollen, food going down the wrong pipe)
Histamine and prostaglandins produced in response to allergies and inflammation
Lung hyperinflation


What do peripheral sensors in the carotid bodies and aortic bodies do?

Detect primary arterial PO2 and PCO2- informing the central respiratory control centre if more ventilation is required in order to maintain blood gases at appropriate levels


Where are carotid bodies located?

At the bifurcation of the common carotid arteries


Describe carotid bodies?

Highly vascularised, high blood flow relative to their metabolic needs, well suited to sense O2 and CO2 levels in the blood and respond to decreases of PaO2 or increases PaCO2


Where do afferent from carotid bodies travel?

Travel in carotid sinus nerve, along with afferent a from the carotid sinus baroreceptors, which joins the glossopharyngeal (XI cranial) nerve as it enters the medulla


Describe aortic bodies?

Found in the aortic arch and subclavian arteries, their afferent a travel in the vagus nerve


Describe central chemoreceptors

Located on the ventral surface of the medulla and are sensitive to the pH of cerebrospinal fluid


What reveals the intrinsic sensitivity of ventilation to O2 and CO2?

Measuring ventilatory response to changing each, in turn, while artificially holding the other constant