Involuntary Regulation of Breathing

Anatomy of Breathing Muscles

• Rib Cage Muscles: Intercostal muscles
• Diaphragm: Key muscle under the rib cage

Mechanism of Breathing

• Inhalation/Exhalation: Muscles contract and relax
• Brain Signals: Required for muscle contraction

Voluntary vs Involuntary Breathing

• Voluntary Breathing: Control over breathing (e.g., holding breath underwater)
• Involuntary Breathing: Happens without conscious effort (e.g., breathing during sleep)
• Conclusion: Breathing is both voluntary and involuntary, focus on involuntary regulation

Brain Regions Controlling Breathing

• Pons and Medulla Oblongata: Lower part of the brain
• Neurons Involved:
  • Dorsal Respiratory Group (DRG): Located in medulla oblongata, controls diaphragm & intercostal muscles
  • DRG Function: Fires constant nerve impulses for muscle contraction (inhalation)
  • Pneumotaxic Center: Located in pons, switches off DRG for exhalation (3-5 secs)
  • Rate of Breathing: Pneumotaxic center switches off DRG 12-16 times/minute

Response to Physical Exercise

• Increased Breathing Rate: During exercise
• CO2 Production: Increased during physical activity
• Blood Acidity: High CO2 lowers pH (more acidic)
• Chemoreceptors:
  • Peripheral Chemoreceptors: Located in carotid artery & aortic arch, detect increased H+ and CO2
  • Central Chemoreceptors: Located near medulla, detect changes in cerebrospinal fluid

Action of Chemoreceptors

• Signal Transmission: Send signals to the pneumotaxic center
• Pneumotaxic Response: Increases rate and depth of breathing

Key Points

• Neural Control: Involves DRG (medulla) and pneumotaxic center (pons)
• Chemical Control: Involves chemoreceptors detecting changes in blood and cerebrospinal fluid
• Combined Effort: Both neural and chemical controls regulate involuntary breathing

Summary

• Neural Control: DRG initiates inhalation; pneumotaxic center controls exhalation
• Chemical Control: Chemoreceptors respond to CO2/H+ levels, impacting breathing rate/depth

Important Terms

• DRG (Dorsal Respiratory Group): Medulla, initiates inhalation
• Pneumotaxic Center: Pons, controls exhalation
• Peripheral Chemoreceptors: Carotid artery, aortic arch
• Central Chemoreceptors: Near medulla, cerebrospinal fluid