Respiratory Physiology Course Quiz

Course Objectives

• Understand structure and functions of the respiratory system.
• Identify air passage from exterior to alveoli.
• Recognize major muscles involved in respiration and their roles.
• Explain the breathing mechanism.
• Comprehend pulmonary blood flow and circulation dynamics.
• Discuss pulmonary ventilation, lung compliance, and the role of surfactants.
• Define lung volumes, capacities, and pulmonary function tests.
• Analyze the composition of inspired, expired, and alveolar air, along with dead space.
• Explain respiratory gas transport.
• Describe respiratory control under various conditions like exercise, high altitude, and deep sea.

Introduction

• Respiration involves the exchange of gases (O2 and CO2) between organisms and the environment.
• Aimed at delivering oxygen to tissues and removing carbon dioxide.
• Collaboration between the respiratory and cardiovascular systems forms the cardiopulmonary system.

Physiological Anatomy

• The respiratory system comprises the nose, pharynx, larynx, trachea, bronchi, bronchioles, and lungs.
• Divided into:
  • Upper respiratory system: Nose, nasal cavity, pharynx.
  • Lower respiratory system: Larynx, trachea, bronchi, lungs.
• The conducting zone includes nasal cavity to terminal bronchioles, filtering and moisten air.
• The respiratory zone encompasses respiratory bronchioles, alveolar ducts, sacs, and alveoli for gas exchange.
• Normal arterial blood oxygen saturation is about 97% with a PO2 of 95 mm Hg.

Oxygen-Hemoglobin Dissociation Curve

• P50: The PO2 at which hemoglobin is 50% saturated with oxygen, typically 25-27 mm Hg.
• Shifts in curve:
  • Right shift: Indicates decreased affinity of hemoglobin for oxygen, occurs with decreased pH, increased temperature, high CO2, or excess 2,3-BPG.
  • Left shift: Indicates increased affinity for oxygen, occurs with increased pH, decreased temperature, and presence of fetal hemoglobin.

Bohr and Haldane Effects

• Bohr Effect: Increased CO2 decreases hemoglobin affinity for oxygen.
• Haldane Effect: Binding of oxygen to hemoglobin displaces CO2 from hemoglobin, facilitating CO2 release into alveoli.

Control of Respiration

• Governed by nervous and chemical mechanisms.
  • Nervous control: Involves neurons in the medulla oblongata and pons:
    • Dorsal respiratory group: Responsible for inspiration.
    • Ventral respiratory group: Responsible for expiration.
    • Pneumotaxic center: Regulates breathing rate and depth.

Respiratory Changes in High Altitude

• High altitude (above 8,000 feet) results in decreased atmospheric pressure and lower oxygen availability, causing hypoxia.
• Acclimatization strategies include:
  • Increased pulmonary ventilation through chemoreceptor stimulation.
  • Enhanced gas diffusing capacity and oxygen transport due to increased RBC production and hemoglobin concentration.
  • Cardiovascular adjustments like increased heart rate and cardiac output.

Important Definitions

• FEV1: The maximum volume of air that can be forcibly exhaled in one second.
• Vital Capacity: Maximum air volume moved in/out during respiration.
• Tidal Volume: Volume of air per normal breath.

Factors Influencing Gas Exchange

• Oxygen enters pulmonary capillaries from alveoli due to concentration gradient (high PO2 in alveoli vs. low in capillaries).
• Tissue cells receive oxygen based on local metabolic demands.
• Hemoglobin affinity for O2 decreases with increased CO2, lowered pH, elevated temperature, and raised 2,3-BPG.

Modifications in Breathing

• Brain cortex, CO2 & O2 levels, proprioceptors, inflation reflex, temperature changes, pain, and airway irritation all modify breathing patterns.

Key Questions

• What nerve controls diaphragm contraction during breathing?
• Differential responses of peripheral chemoreceptors to hypoxia, acidosis, and hypercapnia.
• How does exercise affect the oxygen-hemoglobin dissociation curve, enhancing O2 delivery to tissues.