Lecture Notes on Breathing and Respiration

Introduction

• Breathing vs Respiration: Different processes; often confused.
• NEET exam humor: Emphasizing motivation and focus on studies.
• Chapter Overview: Breathing & Exchange of Gases.

Breathing vs Respiration

• Breathing: Exchanging oxygen (O2) from the atmosphere with carbon dioxide (CO2) produced in cells.
• Respiration: Cellular process using O2 to break down glucose (producing ATP and CO2).

Respiratory System Anatomy

• Main Goal: Transport O2 to tissues; remove CO2 from tissues.
• Pathway: External nostrils -> Nasal cavity -> Pharynx -> Larynx -> Trachea -> Bronchi -> Bronchioles -> Alveoli.
• Important Structures:
  • Nostrils/Nasal Cavity: Warms and filters air.
  • Pharynx: Common passage for food and air.
  • Larynx (Voice Box): Contains vocal cords.
  • Trachea: Supported by cartilaginous rings.
  • Bronchi/Bronchioles: Conduct air to alveoli.
  • Lungs: Alveoli are the site of gas exchange.

Mechanism of Breathing

• Inspiration (Inhalation): Diaphragm contracts (flattens), increasing thoracic cavity volume, reducing pressure, drawing air in.
• Expiration (Exhalation): Diaphragm relaxes, decreasing thoracic cavity volume, increasing pressure, pushing air out.

Respiratory Volumes and Capacities

• Tidal Volume (TV): Normal air volume inhaled/exhaled (~500 mL).
• Inspiratory Reserve Volume (IRV): Additional air after TV during deep breath (~2500-3000 mL).
• Expiratory Reserve Volume (ERV): Additional air expelled after TV (~1000-1100 mL).
• Residual Volume (RV): Air remaining after forceful exhalation (~1100-1200 mL).
• Capacities:
  • Inspiratory Capacity (IC): TV + IRV.
  • Functional Residual Capacity (FRC): ERV + RV.
  • Vital Capacity (VC): TV + IRV + ERV.
  • Total Lung Capacity (TLC): TV + IRV + ERV + RV.

Gas Exchange and Transport

• Partial Pressure: Drives gas exchange.
  • Oxygen: High in alveoli -> Low in tissues.
  • CO2: High in tissues -> Low in alveoli.
• Oxygen Transport:
  • Hemoglobin Binding: Forms oxyhemoglobin (HbO2).
  • Influencing Factors: High pO2, low pCO2, low H+ concentration, low temperature.
• CO2 Transport:
  • Dissolved in Plasma: ~7%.
  • Carbaminohemoglobin: ~20-25%.
  • Bicarbonate Ions: ~70%, facilitated by carbonic anhydrase enzyme.

Regulation of Respiration

• Neural Control: Medulla (Respiratory Rhythm Center - RRC) and Pons (Pneumotaxic Center).
• Chemical Control: Chemoreceptors sensitive to pCO2 and H+ in blood.
  • Located in: Medulla, Aortic Arch, Carotid Arteries.
  • Function: Increase breathing rate when pCO2 or H+ levels are high.

Respiratory Disorders

• Asthma: Allergic response causing inflammation of bronchioles.
• Emphysema: Damage to alveolar walls, often due to smoking.
• Occupational Respiratory Disorders: Caused by long-term exposure to dust and particulates in certain industries.

Important Definitions & Formulas

• Breathing Rate: 12-16 breaths per minute.
• Spirometry: Tool to measure lung volumes (except RV).
• Oxygen Dissociation Curve: Relationship between pO2 and hemoglobin saturation.

Tips & Tricks

• Partial Pressure Memory Aid: When a gas is low, its partial pressure is 40 mmHg.
• CO2 Max: 45 mmHg, as it becomes toxic beyond this point.
• O2: Can reach high values like 104 mmHg in alveoli and 95 mmHg in oxygenated blood.

Study Recommendations

• Review Diagrams: Understand respiratory pathway and lung volumes/capacities.
• Read NCERT: Focus on key points and definitions.
• Practice Questions: Use given examples to test understanding.