Regulation of Respiratory Mechanisms

Local Regulation in Tissues

• Carbon Dioxide Levels

  • Increase in CO2 levels results in vasodilation.
  • Smooth muscle relaxes, increasing blood flow and gas exchange.
  • Example: Active skeletal muscle experiences vasodilation.

• Pulmonary Circuit Differences

  • Blood is shunted towards functional alveoli with high oxygen concentration.
  • Ventilation to Perfusion Ratio (V/Q): Blood is not sent to non-functional alveoli (like empty fuel tanks at a gas station).

Neural Control of Respiration

Medulla Oblongata and Pons

• Subconscious Regulation

  • Involves the medulla oblongata and pons.
  • Medulla oblongata houses the primary respiratory centers.

• Voluntary Regulation

  • Involves higher order brain areas like the cerebral cortex.

Respiratory Centers

• Dorsal Respiratory Group (DRG)

  • Functions with automaticity, similar to cardiac tissue.
  • Responsible for inhalation (inspiratory center).
  • Active at ~2-second intervals during quiet breathing.

• Ventral Respiratory Group (VRG)

  • Active during forced inhalation and exhalation.
  • Communicates with DRG to enhance forced breathing.

• Pontine Centers

  • Apneustic Center: Stimulates DRG to increase inhalation.
  • Pneumotaxic Center: Inhibits apneustic to aid in exhalation.

Respiratory Stimuli

• Chemical Stimuli: Chemoreceptors detect pH and CO2/O2 levels.
• Baroreceptors: Detect stretch and blood pressure.
• Irritants: Cause reflex actions like sneezing or coughing.

Chemo Receptors

• Peripheral: Located in carotid and aortic bodies.
  • Detect blood pH and oxygen levels.
• Central: Located in medulla oblongata.
  • Detect CO2 and pH of cerebrospinal fluid.

Conditions Affecting Respiration

• Hypercapnia: Elevated blood CO2 due to hypoventilation.

  • Causes: Obstruction, neural inhibition, drugs.
  • Response: Increased breathing rate.

• Hypocapnia: Low blood CO2 due to hyperventilation.

  • Reduced stimulation of respiratory rate.

Reflexes and Responses

• Hering-Breuer Reflexes

  • Inflation Reflex: Prevents overexpansion of lungs.
  • Deflation Reflex: Ensures lungs are not underinflated.

• Noxious Stimuli: E.g., debris causing sneezing or coughing.

Influence of Higher Brain Centers

• Voluntary control, anxiety, stress, and excitement affect breathing.
• Exercise: Sympathetic system enhances respiratory rate in anticipation of activity.

These notes cover the mechanisms at both local tissue levels and neural control levels for regulating respiration, as well as the involvement of various brain regions and reflexes in maintaining respiratory homeostasis.