Regulation of Breathing

Question 1

Medullary Respiratory Center

Answer 1

• Part of central control in brain stem and cerebral cortex
• Located in the reticular formation
• Contains dorsal respiratory group and ventral respiratory group

Question 2

Dorsal Respiratory Group

Answer 2

• Part of medullary respiratory center
• Primarily responsible for inspiration
• generates basic rhythm for breathing
• Input comes from vagus and glossopharyngeal nerves
  
  • vagus input: lung chemoreceptors and mechanoreceptors
  • Glossopharyngeal input: peripheral chemoreceptors
• Output: phrenic nerve to diaphragm

Question 3

Ventral Respiratory Group

Answer 3

• Part of Medullary respiratory center
• Primarily responsible for expiration
• Not active during normal quiet breathing when expiration passive
• Activated during exercise when expiration is active process

Question 4

Apneustic Center

Answer 4

• Located in the lower pons
• Stimulates inspiration
• Produces deep and prolonged inspiratory gasp: apneusis

Question 5

Pneumotaxic center

Answer 5

• Located in upper pons
• Inhibits inspiration
• Regulates inspiratory volume and respiratory rate

Question 6

Cerebral Cortex

Answer 6

• Breathing can be under voluntary control
• Person can voluntarily hyperventilate or hypoventilate
• Hypoventilation (breath-holding) limited by increase in pCO2 and decreased pO2
• Previous period of hyperventilation extends period of breath holding

Question 7

Central chemoreceptors in the medulla

Answer 7

• Sensitive to pH of CSF
  
  • decreases in pH of CSF increases breathing rate
• H+ doesn’t cross BBB as well as CO2
• CO2 diffuses from arterial blood into CSF b/c lipid soluble
• In CSF, CO2+H2O produces H+ and HCO3-
  
  • H+ acts directly on central chemoreceptors
• Increases in pCO2 and H+ stimulate breathing
• Decrease in pCO2 and H+ inhibit breathing
• hyperventilation and hypoventilation return arterial pCO2 to normal

Question 8

Peripheral chemoreceptors in carotid and aortic bodies

Answer 8

• carotid bodies located in bifurcation of common carotid arteries
• aortic bodies located above aortic arch
• Decreases in arterial pO2
  
  • stim peripheral chemoreceptors & increase breathing rate
  • pO2 <60, breathing rate very sensitive to pO2
• Increase in arterial pCO2: stim peripheral chemoreceptors and increase breathing rate
  
  • potentiate breathing stimulation caused by hypoxemia
  • peripheral response to CO2 less important than central response to CO2 or H+
• Increases in arterial H+
  
  • stimulate carotid body chemoreceptors directly
  • Metabolic acidosis: breathing rate increased b/c pH down

Question 9

Lung stretch receptors

Answer 9

• Located in smooth muscle of airways
• stimulated by distention of the lung
• Produce reflex decrease in breathing frequency
• Hering-Breuer reflex

Question 10

Irritant receptors

Answer 10

• located between airway epithelial cells

- stimulated by noxious substances (dust/pollen)

Question 11

J (juxtacapillary) receptors

Answer 11

• Located in alveolar walls, close to the capillaries
• Engorgement of pulmonary arteries (LT heart failure) stimulates J receptors
  
  • cause rapid, shallow breathing

Question 12

Joint and muscle receptors

Answer 12

• Activated during movement of the limbs

- Involved in early stimulation of breathing during exercise