3.2.4 Regulation and Control of Breathing

Question 1

Describe the negative feedback respiratory control system

Answer 1

Central controller
- Dorsal resp. group neurons fire spontaneously (inhalation)
- Ventral resp. group exercise only (inhalation and exhalation)
- Pontine respiratory group

Effectors: (output)
- respiratory muscles

Sensors: (input)
- Chemoreceptors
- Lung receptors

Question 2

Effect of cortex on respiratory control

Answer 2

Can override function of brainstem for voluntary hypo- or hyperventilation

Question 3

What is Sudden infant death syndrome?

Answer 3

Uncoordinated respiratory muscle activity
Diaphragm contracts at same time as exhalation

Question 4

What is Cheyne-Stokes ventilation or periodic breathing?

Answer 4

Ventilation oscillates between pnoea (no breathing) and hyperpnoea (gasping and hyperventilation)

Question 5

Role of central chemoreceptors

Answer 5

Respond to changes in chemical composition of blood

↑ H+ = ↑ ventilation

Question 6

Role of peripheral chemoreceptors

Answer 6

Carotid bodies and aortic bodies
Excited by ↑PCO2 or H+ or ↓PO2
Induce a reflex ↑in breathing

Question 7

What are the four lung receptors?

Answer 7

Pulmonary stretch receptors (slowly adapting pulmonary stretch receptors)

Irritant receptors (rapidly adapting pulmonary stretch receptors)

J receptors (juxtacapillary - in alveolar walls close to capillaries)

Bronchial C-fibers

Question 8

Effect of O2 on respiratory centre?

Answer 8

Not much effect
Effect peripheral chemoreceptors if below PO2 70mmHg

Question 9

Neuronal control of airway diameter

Answer 9

Parasympathetic - ACh acts on M3 receptors causing broncial smooth muscle contraction

Sympathetic - (not humans) NANC

Question 10

Explain the NANC system

Answer 10

Non- adrenergic Non-cholenergic system

Efferent fibres via vagus
- Neurotransmittter VIP
- Promoted NO production = airway relaxation

Question 11

Hormonal control of airway diameter

Answer 11

Adrenaline acts on 𝛃2 adrenergic receptors in airways to increase airway diameter

Question 12

Physical factors causing bronchoconstriction

Answer 12

• Mechanical stimulation
• Particulate inhalation
• Aerosol of water
• Cold air
• Chemicals

Question 13

Respiratory response to haemorrhage

Answer 13

Loss of RBCs

↓ O2 carrying capacity and ↓blood flow

Anaemia, hypoxia, acidosis

Stimulation of chemoreceptors

Medullary respiratory neurones = respiratory stimulation
Vasomotor centre = ↑ vasoconstrictor discharge