Main components of the ventilatory system. The ventilatory system is responsible for maintaining the arterial carbon dioxide tension (PaCO2) within normal limits by adjusting minute ventilation (V) to match the rate of carbon dioxide production. The main elements of ventilation are the respiratory pump, which generates a pressure gradient responsible for air flow, and the loads that oppose such action. The machinery of the respiratory pump includes the cerebrum, brain stem, spinal cord, phrenic and intercostal nerves, and the muscles of respiration. Inspiratory muscle contraction lowers pleural pressure (Ppl) thereby inflating the lungs (AV). The diaphragm, the most important inspiratory muscle, moves downward as a piston at the floor of the thorax, raising abdominal pressure (Pabd). The inspiratory decrease in Ppl by the respiratory pump must be sufficient to counterbalance the opposing effect of the combined loads, including the airway flow resistance, and the elastic recoil of the lungs and chest wall. The ventilatory requirement influences the load by altering the frequency and depth of the ventilatory cycle. The strength of the respiratory pump is evaluated by the pressure generated (AP = Ppl - Pabd).

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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