Control of ventilation

Question 1

Minute ventilation=?

Answer 1

breathing frequency x tidal volume

minus dead space
=about 3.5L/min at rest

Question 2

What three situations might increase the amount of breathing?

Answer 2

• Exercise
• Altitude
• Disease

Question 3

What makes up the respiratory centre?

Answer 3

The medulla oblongata and the pons

Question 4

Does the pons regulate the medulla or does the medulla regulate the pons?

Answer 4

Pons regulates the medulla

Question 5

What are the two parts of the pons?

Answer 5

Pneumotaxic centre and the apneustic centre

Question 6

What are the two parts of the medulla?

Answer 6

Dorsal respiratory group and ventral respiratory group

Question 7

What does the pneumotaxic centre do?

Answer 7

Inhibits the DRG

Question 8

What does the apneustic centre do?

Answer 8

Stimulates the DRG

Question 9

What does the DRG do?

Answer 9

Causes inspiration.

Question 10

What does the VRG do?

Answer 10

Initiates inspiration and expiration, only in use during exercise/time of increased ventilation

Question 11

What is the relationship between the DRG and VRG?

Answer 11

Reciprocal inhibition- they inhibit each other creating rhythmical breathing.

Question 12

Which nerves run from the DRG and VRG to innervate the diaphragm and intercostal muscles?

Answer 12

Phrenic and intercostal nerves

Question 13

What are 9 ways the respiratory centre can be controlled?

Answer 13

1. Overriden by cortical control
2. Hypothalamus- emotional or sensory reflex (pain/cold) stimuli
3. Central chemoreceptors
4. Peripheral chemoreceptors
5. Pulmonary stretch receptors
6. Irritant/cough receptors
7. Muscle/joint stretch receptors
8. Baroreceptors
9. J-receptors

Question 14

Where are pulmonary stretch receptors located?

Answer 14

Bronchi and trachea

Question 15

Where are irritant/cough receptors located? What does stimulation of them do?

Answer 15

Throughout the airways. Cough receptor = cough (explosive exhalation) and irritant recpetor= hyperpnoea, airway constriction.

Question 16

What afferent nerve runs from the pulmonary stretch receptors and irritant/cough receptors to the medulla?

Answer 16

Vagus nerve

Question 17

Where are the muscle/joint receptors and proprioceptors located?

Answer 17

Diaphragm, intercostal and other muscles (exercise)

Question 18

Where are baroreceptors located? What do they sense?

Answer 18

Blood vessels, sense blood pressure (high BP= low ventilation)

Question 19

Where are J receptors located? What do they sense?

Answer 19

Next to alveolar capillaries, sense ‘trauma’ e.g. pneumonia, pulmonary oedema, inflammatory agents and increase ventilation in response.

Question 20

Where are peripheral chemoreceptors located? What do they sense?

Answer 20

Carotid artery and aorta, sense hypoxia, hypercapnia and acidosis

Question 21

Which cell senses hypoxia? How?

Answer 21

Glomus cell. Hypoxia causes an influx of Ca2+ via depolarisation. This triggers the release of neurotransmitters which stimulate an action potential in the afferent nerve.

Question 22

Where are central chemoreceptors located? What do they measure?

Answer 22

Near the medulla and also near a rich blood supply. They measure H+ levels by measuring CO2 levels (as this can cross the BBB whereas H+ can’t)