Physiology Chapter 9 Flashcards

Dead Space in the Respiratory System

• Anatomical Dead Space: Composed of the conducting zone; no gas exchange; includes areas without capillary blood supply.
• Physiological Dead Space: Combination of anatomical dead space and alveoli without blood supply.

Airflow Dynamics

• Air flows in response to pressure gradients overcoming resistance.

Composition of Atmospheric Air

• Correct Composition: Atmospheric air is approximately 20.93% oxygen, 0.03% carbon dioxide, and 79.04% nitrogen.

Effects of Altitude on Oxygen Levels

• Percentage of oxygen in air remains consistent as altitude increases; barometric pressure decreases.

Hyperventilation and Breath Holding

• Hyperventilation does not effectively lengthen breath-holding time or significantly increase arterial oxygen partial pressure (PAO2).

Oxygen Transport in Blood

• Only 1.5-3% of oxygen is transported dissolved in blood plasma; this fraction is responsible for determining the blood's partial pressure of oxygen (PO2).

Hemoglobin and Blood Oxygen Saturation

• In arterial blood with a PO2 of 95 mmHg, hemoglobin saturation is approximately 97%.

Characteristics of Pulmonary Venous Blood

• Not all pulmonary venous blood is fully oxygenated under normal circumstances.

Respiration and Exercise Limitation

• Respiration does not serve as a major limiting factor in exercise for healthy, moderately fit individuals.

Ventilation Response to Exercise

• Minute ventilation shows an initial rapid increase during exercise, maintained for about 20-30 seconds, followed by a gradual rise to a steady state.

Indicators of Internal Respiration

• The arterio-venous oxygen difference (a-vO2 diff) serves as a key indicator of internal respiration efficiency.

Workload and Ventilatory Thresholds

• Higher ventilatory thresholds correlate with greater endurance activity intensity that can be sustained.

Importance of PaO2 During Exercise

• Maintaining arterial oxygen (PaO2) during exercise is crucial for effective gas exchange, particularly regarding the oxygen transfer across the alveolar-capillary interface.

Altitude Training and Athletic Performance

• Athletes training at high altitudes can enhance performance in competitions at the same altitude shortly after training, with no consistent effect at sea level.

Neural Control of Respiration

• Dorsal Respiratory Group: Originates impulses to stimulate inspiratory muscles.
• Ventral Respiratory Group: Maintains inspiratory tone and stimulates expiratory muscles.

Impulse Regulation in Respiration

• Pneumotaxic Center: Transmits inhibitory signals to the inspiratory center and plays a role in regulating breathing rhythm.
• Apneustic Center: Continuously stimulates the inspiratory center unless inhibited.

Influence of Emotions on Ventilation

• The hypothalamus can stimulate or inhibit pulmonary ventilation based on factors like pain or strong emotions.

Conscious Control of Breathing

• The cerebral cortex is responsible for voluntary control of pulmonary ventilation; however, it is overridden by high PCO2 levels.

Anticipatory Responses in Exercise

• The cerebral cortex also initiates an anticipatory rise in ventilation rates before exercise begins.

Mechanoreceptors and Exercise Adaptations

• Proprioceptors in muscles and joints stimulate increased pulmonary ventilation during physical activity.

Chemoreceptors and Ventilation

• Central Chemoreceptors: Sensitive to rising PCO2 and decreasing pH, stimulating ventilation.
• Peripheral Chemoreceptors: Responsive to low PO2 and high potassium (K) levels; also stimulate ventilation.

Key Respiratory Equations

• Air Flow (P/R): Represents the relationship between pressure and resistance in airflow.
• Minute Ventilation (Vt * F): Calculated by multiplying tidal volume (Vt) by breathing frequency (F).
• Alveolar Ventilation ((Vt-Vd) * F): Quantity of fresh air reaching alveoli, incorporating dead space (Vd).
• Inspiratory Capacity (IRV + Vt): Total volume of air that can be inspired after normal expiration.
• Total Lung Capacity (IRV + Vt + ERV + RV): Overall lung volume encompassing all air in the lungs.
• Functional Residual Capacity (ERV + RV): Volume of air remaining in the lungs after normal exhalation.
• Vital Capacity (IRV + Vt + ERV): Total volume of air that can be exhaled after maximal inhalation.
• Partial Pressure of a Gas (Pb * Fg): The fraction of total pressure contributed by a specific gas.
• Percent Saturation of Blood with Oxygen ((Hb combined with O2 / Hb capacity to combine with O2) * 100): Measures how much oxygen is bound to hemoglobin relative to its maximum capacity.
• A-vO2 Difference (aO2 - Vo2): Indicates the difference in oxygen content between arterial and venous blood, reflecting oxygen use by tissues.