Control of Ventilation

Question 1

In neural control of ventilation, what type of receptors are involved?

Answer 1

Lung stretch receptors

Question 2

In chemical control of ventilation, what type of receptors are involved?

Answer 2

Central and peripheral chemoreceptors

Question 3

Which are of the brain is involved with ventilation?

What is this area of the brain called?

Answer 3

In the pins and medulla, located within the respiratory centre (also called central pattern generator).

Question 4

What X2 areas that are connected with breathing are located within the pons, and what do they each do?

Answer 4

They are the pneumotaxic and apneustic centres, which are both involved in inspiration.

Pneumotaxic = inhibits inspiration

Apneustic = prolongs inspiration

Question 5

What X3 areas that are connected with breathing are located within the medulla, and what do they each do?

Answer 5

1) dorsal respiratory group within the nucleus tractus solitarius.
= these are the inspiratory neurons of normal “quiet” breathing and relay the message to the phrenic nerve
= cease of firing of these neurons causes passive expiration
= the DRG receives both lung receptor and chemoreceptor input

2) ventral repsiratory group within the nucleus ambiguus and nucleus retroambiguus
= INACTIVE during normal quiet breathing
= these neurons fire during active breathing, both for inspiratory and expiratory muscles (but show reciprocal inhibition = one inhibits the other so they can not oppose and summate at the same time)

3) pre-bötzinger complex within the nucleus retrofacialis
= centre of respiratory rhythmogenesis

Question 6

What pathway do we use for voluntary breathing if we want to override our central pattern generator?

Answer 6

The pyramidal tracts.

Question 7

What are the X4 types of lung receptors?

Answer 7

1) stretch
2) juxtapulmonary (J)
3) irritant
4) proprioreceptors

Question 8

Where are the lung stretch receptors found?

Answer 8

Within the smooth muscle of the bronchiole walls

Question 9

Explain the deflation reflex.

Answer 9

Deflation stimulates inspiration.

Question 10

Where are the juxtapulmonary (J) receptors located?

Answer 10

In the alveolar/bronchial walls close to the capillaries.

Question 12

Which receptors are responsible for the deep augmented breaths we take every 5-20 minutes and why?

Answer 12

The irritant receptors responding to the gradual/slow collapse of the lungs over time during quiet breathing.

Question 13

Where are proprioreceptors located?

Answer 13

In the respiratory muscles.

Question 14

Where are irritant receptors found?

Answer 14

All throughout the airways.

Question 15

What is the relationship graphically between PACO2 and ventilation?

Answer 15

They are linear; as PACO2 increases so does ventilation to match.

At the extremes this relationship ‘tails off’.

NB: ventilation in these graphs is not the same as respiratory rate, it is a volume measured in L/min.

Question 16

What happens to the ventilation-PACO2 graph line to compensate for metabolically derived changes in pH?

Answer 16

It shifts to the right or left accordingly to compensate is respiratory effort.

E.g. metabolic acidosis/alkalosis with compensatory respiratory acidosis/alkalosis…

Question 17

What is the relationship graphically between PAO2 and ventilation?

Answer 17

Anything above 8kPa PAO2, ventilation stays at a controlled 8-10L/min.

As PAO2 drops below 8kPa, it begins to stimulate ventilation increases steeply.

Question 18

What does hypercapnia do to the PAO2-ventilation graph line?

Answer 18

It moves it upwards, meaning the same relationship exists with PAO2 and ventilation however for the same PAO2 the ventilation volume seen is higher.

Question 19

What is meant by hypoxia and hypercapnia working synergistically?

Answer 19

The effect of the two of them together is stronger than separately.

Question 20

What do central chemoreceptors respond to?

Answer 20

Changes in the pH of CSF, as the blood H+ ions can not cross the blood-brain barrier to the chemoreceptor.

They also respond to PaCO2 as gasses can cross the blood-brain barrier.

Question 21

Where are the peripheral chemoreceptors found?

Answer 21

In the:

1) aortic bodies (in the aortic arch)
2) in the carotid sinus (where the common carotid artery bifurcates)

Question 22

Which nerves innervate the:

1) aortic bodies
2) in the carotid sinus

Answer 22

1) the vagus

2) the glossopharyngeal

Question 23

What are the X2 cell types which are found in the carotid bodies?

Answer 23

Type 1 glomus cells

Type 2 sheath cells
= party enclose around type 1 cells

Question 24

What do aortic and carotid bodies respond to?

Answer 24

Increases in PCO2

Decreases in PO2

Increase in pH

Question 25

What condition leads to periods of progressive, faster breathing followed by long periods of apnea, which results in the rise and fall of O2 saturations?

Answer 25

Cheyenne-stokes respiration

Question 26

What is the main difference between central and obstructive sleep apnoea?

Answer 26

In obstructive, the airways collapse but a respiratory effort still remains.

In central, it is the respiratory effort which stops.

Question 27

What condition is a for, of brainstem damage which results in respiratory arrest during sleep?

Answer 27

Ondine’s curse.