呼吸科呼吸系统英文版.ppt

EXERCISE AND VENTILATION Exercise Is Associated with Hyperventilation Rest Maximal Exercise Intensity 6 100 Acute Respiratory Response to Graded Dynamic Exercise Exercise Intensity Ventilation (L/min) V/Q PAO2 (mm Hg) PaO2 (mm Hg) PaCO2 (mm Hg) Arterial pH Rest 5 1 103 100 40 7.40 Walking 20 2 103 100 40 7.40 Jogging 45 3 106 100 36 7.40 Running 75 4 110 100 25 7.32 Conclusion Hyperventilation during exercise is primarily caused by mechanisms beyond chemical changes in the blood The cortex sends signals to the basic respiratory center? Is there interaction between the cardiovascular and basic respiratory centers ? MECHANICAL REFLEXES Several mechanical reflexes that arise from the chest wall and lungs affect ventilation and ventilatory patterns. Receptors Are Localized in Lung Tissue and Airways Pulmonary receptors can be divided into 3 groups: pulmonary stretch, irritant and J receptors. Afferent fibers of all three types lie predominantly in the vagal nerves. Pulmonary Stretch Receptors The stretch receptors are sensory terminals of myelinated afferent fibers that lie within the smooth muscle layer of conducting airways. The stretch receptors sense changes in lung volume. The stretch receptors mediate lung inflation refelx (Hering-Breuer reflex). Lung Stretch Reflexes Pulmonary inflation reflex (Hering-Breuer inspiratory-inhibitory reflex) Inflation of lungs or stretch of airways switches from inspiration to expiration. As a result, inspiration is shortened with increased breathing rate. Pulmonary deflation reflex: Deflation of lungs promotes inspiration is called pulmonary deflation reflex. Both are mediated by the vagal fibers; cutting of vagal nerve either unilaterally or bilaterally could deepen and prolong inspiration. ?? More about the Hering-Breuer Inspiratory-Inhibitory Reflex The Hering-Breuer inspiratory-inhibitory reflex (pulmonary inflation reflex) is stimulated by increases in lung volume. This stretch reflex is med