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RESPIRATORY MUSCLE CONTRACTION A. Inspiration (inhalation) 1. active process (requires skeletal muscle contraction) 2. Diaphragm a. creates pressure difference between intrapleural space and abdominal cavity (abdominal pressure usually assumed to be negligible) b. D P ~ Tension in diaphragm ( D P ~ T / radius of curvature; note inefficiency of flat diaphragm) c. responsible for about 2/3 of inspired volume in quiet breathing (diaphragm descends a few cm in quiet breathing, more in vigorous breathing; ==> ) d. last respiratory activity to be effected by CNS depression ("abdominal breathing") 2. Intercostal muscle contraction, particularly external intercostals a. raise rib cage, thus increasing chest anterior-posterior dimension B. Expiration (exhalation) 1. Quiet breathing a. passive b. due to elastic recoi...

VENTILATION PARAMETERS A. Lung Volumes ( ==> ) 1. Basic volumes: elements a. Tidal Volume (V T , TV): volume of gas exchanged each breath -- can change as ventilation pattern changes b. Inspiratory Reserve Volume (IRV): maximum volume that can be inspired, starting from the end inspiratory position -- potential volume at the end of inspiration c. Expiratory Reserve Volume (ERV): maximum volume that can be expired, starting from the end expiratory position -- potential volume at the end of expiration d. Residual Volume (RV): volume remaining in the lungs and airways following a maximum expiratory effort -- lungs cannot empty completely because of (1) stiffness when compressed and (2) airway collapse and gas trapping at low lung volumes 2. Capacities: combined volumes a. Vital Capacity (VC): maximum volume of gas that can be exchanged in a single breath VC...