volumes
DESCRIPTION
Volumes. Tidal Volume (TV) = volume of air during one resting respiratory cycle. Expiratory Reserve Volume (ERV) = volume of air that can be forcefully expired, following a resting expiration. - PowerPoint PPT PresentationTRANSCRIPT
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Volumes
Tidal Volume (TV) = volume of air during one resting respiratory cycle.
Expiratory Reserve Volume (ERV) = volume of air that can be forcefully expired, following a resting expiration.
Inspiratory Reserve Volume (IRV) = Volume of air that can be forcefully inspired, following resting inspiration.
Residual Volume (RV) = Volume of air that remains in lungs. About 1200mL.
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Capacities
Vital Capacity (VC) = maximal amount of air that can be expired after maximal inspiration.VC = TV + IRV + ERV
Functional Residual Capacity (FRC) = Amount of air that remains in lungs following a relaxed expiration.FRC = ERV + RV
Total Lung Capacity (TLC) = Maximal volume of air in lungs.TLC = RV + ERV + TV + IRV or TLC = VC + RV
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Inspiration.a. Relaxed inspiration. Diaphragm and external intercostal muscles contract.
b. Forceful inspiration. Diaphragm and external intercostal are supplemented by the sternocleidomastoid and pectoralis minor muscles.
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Expiration. a. Normal expiration is due to elastic recoil of lungs and abdominal organs.
b. Forceful expiration is supplemented by the internal intercostal muscles and abdominal wall muscles.
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Factors Affecting Breathing
1. Medullary Respiratory Center – detects changes in CO2 and H+ (pH) concentrations• Major Stimulus for breathing
2. Carotid Bodies & Aortic Bodies – detects changes in O2 concentrations
CO2 + H2O H2CO3 HCO3- + H+
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Hering-Breuer Reflex: • Stretch receptors in lung tissues are stimulated during inspiration. • Sensory impulses travel via the vagus nerve to the pneumotaxic center of the respiratory
center in the pons. • Duration of inspiration shortens. Prevents overinflation.
CO2 + H2O H2CO3 HCO3- + H+