Neural control of breathing

Question 1

What factors increase to increase total O2 transported?

Answer 1

Ventilation increases alongside cardiac
output to increase total O2 transported

Question 2

How is O2 delivery increased in healthy, exercising individuals?

Answer 2

In healthy, exercising individuals,
increased O2 delivery achieved by
increasing cardiac output, not PaO2

Question 3

Which muscle is utilised in quiet breathing for inspiration?

Answer 3

Diaphragm

Question 4

Which muscle is utilised in quiet breathing for expiration?

Answer 4

Elastic recoil

Question 5

Which respiratory muscle is utilized in increased/forced breathing for inspiration?

Answer 5

External intercostals

Question 6

Which respiratory muscle is utilised in increased/forced ventilation for expiration?

Answer 6

Internal intercostals

Question 7

Which respiratory muscle is utilised in increased/forced ventilation for expiration?

Answer 7

Elastic recoil
Internal intercostals

Question 8

Which accessory muscle is utilised in increased/forced ventilation during inspiration?

Answer 8

Pectorals
Sternomastoid

Question 9

Which accessory muscle is utilised in increased/forced ventilation during expiration?

Answer 9

Abdominals

Question 10

What are the steps involved in the basic breathing pattern?

Answer 10

-The basic breathing pattern is generated by neuronal systems within the brainstem
1. Higher centres in the brain stimulate the pontine respiratory group(PGR)
2. PGR stimulates both DRG and VRG
3. The DRG can also be stimulated by central chemoreceptors and sensory input
4. The VRG is responsible for excitatory output and innervation of upper respiratory tract
5. The DRG is responsible for inspiratory output

Question 11

How does the central pattern generator determine the rate and depth of breathing?

Answer 11

1. Higher brain centers(cerebral cortex-voluntary control over breathing)
2. Respiratory centers(medulla and pons)
3. Stretch receptors in lungs
4. Irritant receptors
5. Receptors in muscles and joints
6. Central chemoreceptors
   -Increased CO2, increased H+
7. Peripheral chemoreceptors
   -Decreased O2, Increased CO2, Increased H+
8. Other receptors like pain acting through hypothalamus

Question 12

What does the central pattern generator(CPG) do?

Answer 12

The CPG integrates data from various
neuronal inputs to regulate ventilation

Question 13

What do central chemoreceptors respond to?

Answer 13

Central chemoreceptors respond
(indirectly) to changes in arterial PCO2

Question 14

Where are central respiratory chemoreceptors present in?

Answer 14

Present in the medulla

Question 15

Why do the central respiratory chemoreceptors act indirectly to changes in aretiral PCO2?

Answer 15

Although CRC respond to
changes in [H+] within
cerebrospinal fluid, as H+
does not cross the blood
brain barrier, CRC do not
directly respond to changes
in blood pH (except via CO2

Question 16

What do carotid and aortic bodies respond to?

Answer 16

Peripheral chemoreceptors respond to
changes in arterial O2, CO2, and pH.

Question 17

What are peripheral chemoreceptors activated by?

Answer 17

Activated by ↓PaO2, ↑PaCO2
and acidaemia.

Question 18

What do carotid bodies and aortic bodies signal to and via what nerves?

Answer 18

Signal to respiratory centres in
medulla (via sensory nerves) to
increase ventilation (negative
feedback).

Question 19

What is proportional to PaCO2 in hypercapnic drive?

Answer 19

ventilation is
generally proportional to PaCO2

Question 20

What does hypoxic drive stimulate?

Answer 20

Hypoxic drive – hypoxaemia (low PaO2)
stimulates increased ventilation

Question 21

When does the hypoxic drive kick in?

Answer 21

This drive kicks in only at very low PaO2

Question 22

What is the transition of ventilation from wakefulness to sleep?

Answer 22

-Ventilation decreases during sleep
1. ↓metabolic rate = ↓respiratory demands
2. Postural changes alter mechanics of breathing
3. ↓SNS & ↑PNS tone = ↓HR, BP & CO.
4. ↓tidal volume, ↓breathing frequency, ↓minute volume
5. ↓SaO2 (≈96%), ↑PaCO2 (≈7kPa)
6. ↓upper airway calibre

Question 23

What are examples of pathologies that are associated with dysfunction in central processes that initiate breathing?

Answer 23

• Trauma – damage to respiratory centres in the brainstem
• Stroke – ischaemia-induced brainstem tissue injury
• Drugs (e.g. opioids) – suppression of neuronal activity
• Congenital central hypoventilation syndrome
• Neonates – incomplete development of respiratory centres prior
  to birth
• Altitude – control systems unable to cope with abnormal
  atmospheric environment (i.e. low O2 and low CO2), e.g. Cheyne-
  Stokes respiration

Question 24

What is sleep apnoea?

Answer 24

temporary cessation of breathing during sleep

Question 25

What is sleep apnoea characterized by?

Answer 25

Characterised by >5 episodes per hour lasting >10 seconds.

Question 26

What are the effects on health of sleep apnoea?

Answer 26

• Tiredness (poor sleep quality)
• Cardiovascular complications (stress + ↑SNS tone)
• Obesity/Diabetes (inflammation + metabolic dysfunction)

Question 27

What is cheyne-stokes respiration?

Answer 27

oscillating apnoea and hyperpnoea

Question 28

What are the steps in cheyne-stoke respiration?

Answer 28

1. Hypercapnia/hypoxaemia
   -Pathologies that can induce this are altitude, CR dysfunction, heart failure
2. Leads to compensatory hyperventilation
3. This causes hypocapnia+alkalosis
4. This decreases respiratory drive
   5.This results in compensatory hypoventilaiton
5. Repeats from step 1 again hence cycle