RESPIRATORY SYSTEM BREATHING MECHANISM AND LUNG VOLUMES & CAPACITIES

INSPIRATION  Passive  atmospheric pressure compared to intraalveolar pressure –760 mmHg – atm. Pressure –Diapragm contracts – moves downward  Increase volume: decrease pressure  Air moves in –Added Muscles: external intercostal, sternocleidomastoid, pectoralis minor –surface tension of parietal and visceral pleural membranes –Compliance PRESSURES OF INSPIRATION

EXPIRATION  Elastic Recoil – passive process  Decrease volume: increase pressure –Air moves out  Added force: internal intercostal + abdominal muscles  Non Respiratory Air Movements –Cough, sneeze, laugh, cry, hiccup, yawn, speech

LUNG VOLUMES AND CAPACITIES  Tidal volume (TV) – normal inhale/exhale  Inspiratory Reserve Volume (IRV) – max inhale after normal  Expiratory Reserve Volume (ERV) – max exhale after normal exhale  Residual Volume (RV) – amount left in lungs after max. exhale  Vital Capacity – total volume of max inhale to max exhale –IRV + TV + ERV  Inspiratory Capacity – Max. inhale –IRV + TV  Functional Residual Capacity – amount left in lungs after normal exhale –ERV + RV  Total Lung Capacity – max amount of gas in lungs –IRV + TV + ERV + RV GRAPH

CONTROL OF BREATHING  Rhythmic, involuntary  Respiratory center – medulla oblongata + pons –Medullary rhythmicity center  Dorsal: rhythm  Ventral: forceful breaths –Pneumotaxic area  Rate of breathing  Factors affecting breathing –CO2 and H+ ions –Low O2 –Hering-Bruer Reflex –Emotional upset –Hyperventilation and Holding Breath FACTORS

PRESSURES OF INSPIRATION

FACTORS AFFECTING BREATHRATE

Lung Volumes and Capacities