Chapter 9: Pulmonary System and Physical Activity Flashcards
3 major functions of ventilatory system
- Supply oxygen required in metabolism
- eliminate carbon dioxide produced in metabolism
- regulate hydrogen ion concentration to maintain acid-base balance
Mechanics of Ventilation: Inspiration
Diaphragm contracts, flattens out, moves downward. Air in lungs expands, reducing its pressure.
Mechanics of Ventilation: Expiration
Predominantly passive process, air moves out of lungs from recoil of stretched lung tissue and relaxation of inspiratory muscles
Tidal Volume (TV)
Air moved during inspiratory or expiratory phase of breathing cycle; between 0.4 to 1.0 L of air per breath
Inspiratory Reserve Volume (IRV)
2.5 to 3.5 L above TV; serves as inhalation reserve
Expiratory Reserve Volume (ERV)
After normal exhalation, additional volume exhaled; 1.0 to 1.5 L for men, 10 to 20% lower for women
Forced Vital Capacity (FVC)
Total air volume moved in 1-breath from full inspiration to max expiration; varies with body size and body position when measuring
Residual Lung Volume (RLV)
Following max exhalation,
air volume that cannot be exhaled; 1.2 to 1.6 L for men, 1.0 to 1.2 L for women
Dynamic measures of pulmonary ventilation
- max air volume expired (FVC)
- Speed of moving a volume of air
Physiological Dead Space
Portion of alveolar volume with poor tissue
regional perfusion or inadequate ventilation
Henry’s Law
Amount of gas dissolved in fluid depends on:
– Pressure differential between gas above fluid and
dissolved in it
– Solubility of gas in fluid
Blood transports oxygen in two ways
- Physical solution
- combined with Hb
Cortical Influence
Neural outflow from regions of motor cortex during PA and cortical activation in anticipation of PA stimulate respiratory neurons in medulla
Peripheral Influence
Sensory input from joints, tendons, muscles adjust ventilation during PA
Phase I ventilation
When PA begins, neurogenic stimuli from cerebral cortex and active limbs cause initial breathing increase
Phase II ventilation
Central command input plus medullary control neurons and peripheral stimuli from chemoreceptors and mechanoreceptors contribute to control minute ventilation, gradually increasing to a steady level
Phase III ventilation
“Fine tuning” of ventilation through peripheral sensory feedback mechanism
Despite variations in ventilatory equivalents among health people, complete aeration of blood takes capillaries proceeds slowly enough to allow complete gas exchange
place because of 2 factors
- Alveolar Po2 and Pco2 remain at near-resting value.
- Transit time for blood flowing through pulmonary
Tvent
point at which PV increases disproportionately with VO2 max during graded activity, Relates directly to increased CO2 output from buffering of lactate that begins to accumulate from anaerobic metabolism
Onset of Blood Lactate Accumulation (OBLA)
Occurs between 55 to 65% VO2max in healthy, untrained subjects and often equals >80% VO2max in highly trained endurance athletes, OBLA point increases with aerobic training without accompanying increase in VO2max
Two factors influence endurance performance
- VO2 max
- max level for steady-rate activity (OBLA)
Two factors determine energy requirements of breathing
- compliance of lungs and thorax
- resistance of airways to smooth air flow