Physiology: Control of Ventilation

Question 1

Which nerves are stimulated in ventilation?

Answer 1

Stimulation from skeletal muscles of inspiration - ie the phrenic nerve to the diaphragm and intercostal nerves to the external intercostal muscles

Question 2

Where are the respiratory control centres?

Answer 2

Pons and the medulla

Question 3

Is respiration subconscious?

Answer 3

Normally yes however can be voluntarily modulated

Question 4

Where does signalling to the respiratory system occur on the spinal cord?

Answer 4

C3-5

C3,4,5 keeps the diaphragm a alive

Question 5

What is the function of the Respiratory centres?

Answer 5

Set automatic rhythm by co-ordinating firing smooth and repetitive action potentials in the Dorsal Respiratory Group (DRG) which travel to the inspiratory muscles

Adjusting the rhythm to stimuli

Question 6

What modulates the Respiratory Centres?

Answer 6

1. Emotion (Limbic System)
2. Voluntary Over-ride (Higher brain centres)
3. Mechano-sensory input from thorax (stretch sensitive)
4. Chemical composition of blood (chemoreceptors)

Question 7

What is the most significant modulator of respiratory centres?

Answer 7

Chemoreceptor input

Question 8

What does the Dorsal Respiratory Group of neurons (DRG) supply?

Answer 8

Inspiratory muscles through phrenic and intercostal nerves

Question 9

What does the Ventral Respiratory Group of neurons (VRG) supply?

Answer 9

Tongue
Pharynx
Larynx
Expiratory Muscles

Question 10

What are the 2 types of Chemoreceptors?

Answer 10

Peripheral (Secondary Ventilatory Control) and Central (Primary Ventilatory Control)

Question 11

Where are the Central Chemoreceptors found?

Answer 11

Medulla

Question 12

What do Central Chemoreceptors Detect?

Answer 12

Changes in H+ concentration in CSF of the brain

Question 13

What does a rise of H+ ions caused by raised PCO2 ie hypercapea?

Answer 13

Stimulates Ventilation

Question 14

Does Ventilation directly respond to changes H+ concentration in plasma?

Answer 14

No

Question 15

Can CO2 cross the blood brain barrier?

Answer 15

Yes

Question 16

Can H+ cross the blood brain barrier?

Answer 16

No

Question 17

How do central chemoreceptors monitor partial arterial pressure of CO2?

Answer 17

The monitor PCO2 indirectly

Question 18

What products are formed when CO2 crosses the blood brain barrier?

Answer 18

Bicarbonate and H+

The receptors respond to H+

Question 19

What does increased arterial PCO2 do the ventilation?

Answer 19

Increases Ventilation Rate

Question 20

What does decreased arterial PCO2 do to ventilation?

Answer 20

Slows Ventilation Rate

Question 21

Define the condition Hypoxic Drive?

Answer 21

De-sensitivity to PCO2 and instead relys on PO2 to stimulate ventilation

Question 22

What Disease can cause hypoxic drive?

Answer 22

Chronic Lung Disease due to the elevated PCO2

Question 23

Where are the Peripheral Chemoreceptors found?

Answer 23

Carotid and aortic bodies

Question 24

What do peripheral chemoreceptors detect?

Answer 24

Changes in arterial PO2 (ie arterial oxygen pressure not total oxygen content) and H+ concentration (related to PCO2 in arteries)

Question 25

How do Peripheral Chemoreceptors have an effect of ventilation?

Answer 25

Reflex stimulation of ventilation after a fall of PO2 or rise in H+ concentration

Question 26

How does a fall in plasma pH affect ventilation?

Answer 26

Peripheral chemoreceptors detect increase [H+] and ventilation will be stimulated due to acidosis

Question 27

How does increase in plasma pH affect ventilation?

Answer 27

Peripheral chemoreceptors detect decrease in [H+] (through vomiting) and ventilation will be inhibited due to alkalosis

Question 28

How can we control our breathing?

Answer 28

Neural pathway from cerebral cortex to Resp motor neurons allows voluntary control

Question 29

Are we able to overide our involuntary control?

Answer 29

No due to our chemoreceptors take primary control

Question 30

When is ventilation reflexly inhibited?

Answer 30

Increase in PO2 in arteries and decrease in arterial PCO2 causing Hyperventilation

Question 31

What does breathing in CO2 into our lungs cause to our body?

Answer 31

Bodies are programmed to get rid of CO2 therefore increased alveolar partial pressure of CO2 decreases pressure gradient and therefore increased arterial pressure of CO2 causing high distress

Question 32

What is more uncomfortable, high PaCO2 and normal PaO2, or low PaO2 and No PaCO2?

Answer 32

High PaCO2 and normal PaO2 as your body is made to get rid of CO2

Question 33

What happens respiration during swallowing?

Answer 33

Respiration is inhibited and is followed by expiration to remove any left over food going down the epiglottis

Question 34

Name some drugs that have an effect on the Resp System

Answer 34

Barbiturates and opioids - depress Resp system Anaesthetic agents increase RR Nitrous Oxide (NO) blunts peripheral chemoreceptors response to PaO2 falling

Question 35

Why shouldn't NO be used on patients who have chronic Lung Disease?

Answer 35

As the patients rely on hypoxic drive