Understanding Respiratory Control and Gas Exchange

Apr 3, 2025

Mindmap

Lecture Notes: Respiratory System Control and Gas Exchange

Key Controls of Breathing

1. Respiratory Areas

  • Located in the brain stem (medulla oblongata and pons)
  • Medulla Oblongata: Monitors CO2 levels and hydrogen ions.
    • If levels increase, respiratory rate and depth increase.
  • Pons: Maintains rhythm of breathing, prevents breath-holding and panting.

2. Carotid and Aortic Bodies

  • Chemoreceptors located in the carotid artery and aortic arch.
  • Monitor oxygen levels.
  • Low oxygen levels increase respiratory rate and depth.

3. Inflation Reflex (Hering-Breuer Reflex)

  • Stretch receptors in visceral pleura, bronchioles, and alveoli prevent lung over-inflation.
  • Activation sends impulses down the vagus nerve.

4. Emotional and Physical Responses

  • Fear, pain, and cold increase respiratory rate.

5. Conscious Control

  • Limited ability to control respiration (e.g., holding breath, panting).
  • Eventually overridden by medulla oblongata’s CO2 monitoring.

6. Hyperventilation

  • Rapid breathing clears CO2, can lead to respiratory alkalosis.
  • Brain may assume high oxygen levels, potentially dangerous.

Gas Exchange and Transport

Respiratory Membrane

  • Composed of two layers of cells with a fused membrane.
  • Facilitates diffusion of gases (oxygen and CO2) between alveoli and capillaries.

Dalton's Law of Partial Pressures

  • Total pressure exerted by a gas mixture is the sum of individual gas pressures.
  • Oxygen exerts higher partial pressure due to greater presence.

Gas Transport in Blood

  • Oxygen:
    • 98% carried by hemoglobin, 2% in plasma.
    • Factors affecting binding: CO2 levels, temperature, acidity.
  • Carbon Dioxide:
    • Majority as bicarbonate in plasma, 23% on hemoglobin, 7% in plasma.
    • Hemoglobin carries CO2 and O2 on different sites.

Hypoxia Types

  • Ischemic Hypoxia: Decreased blood flow.
  • Histotoxic Hypoxia: Damaged tissues can’t use oxygen.
  • Anemic Hypoxia: Insufficient hemoglobin.
  • Hypoxic Hypoxia: Low oxygen partial pressure.

Carbon Monoxide Poisoning

  • Competes with oxygen for hemoglobin binding, 200 times stronger.
  • Leads to decreased oxygen transport, potentially fatal.

Cellular Respiration and the Importance of Oxygen

  • Oxygen is critical for ATP production through aerobic respiration.
  • CO2 is a waste product from cellular respiration.
  • Oxygen serves as the final hydrogen acceptor in the electron transport chain.

Summary

  • The respiratory system is essential for maintaining CO2 and O2 balance, crucial for cellular respiration and ATP production.
  • Proper regulation prevents dangerous conditions like hypoxia and respiratory alkalosis.

These notes detail the physiological controls and mechanisms involved in respiration, as well as the importance of maintaining proper gas exchange for cellular function.