Respiratory System 6

Question 1

What is alveolar volume?

Answer 1

The difference between the tidal volume and the dead space volume

Question 2

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

Answer 2

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

Question 3

What are the consequences of hyperventilation?

Answer 3

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)

Question 4

Consequences of Hypoventilation?

Answer 4

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)

Question 5

What is anoxia?

Answer 5

Absence of oxygen

Question 6

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

Answer 6

Highest arterial O2

Question 7

What does breathing rely on?

Answer 7

Neural input to the muscles of ventilation

Question 8

Where does respiratory rhythm originate?

Answer 8

In the brainstem

Question 9

What generates the basic respiratory rhythm?

Answer 9

Two groups of neurons in the medulla oblongata

Question 10

What are the medullary centres?

Answer 10

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)

Question 11

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

Answer 11

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

Question 12

Where are slowly adapting stretch receptors located?

Answer 12

In the walls of the bronchi and bronchioles

Question 13

What do slowly adapted stretch receptors do?

Answer 13

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

Question 14

What are irritant receptors?

Answer 14

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

Question 15

What do irritant receptors respond to?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Where are carotid bodies located?

Answer 17

At the bifurcation of the common carotid arteries

Question 18

Describe carotid bodies?

Answer 18

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

Question 19

Where do afferent from carotid bodies travel?

Answer 19

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

Question 20

Describe aortic bodies?

Answer 20

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

Question 21

Describe central chemoreceptors

Answer 21

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

Question 22

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

Answer 22

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