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part of the lung than in the upper part. On the other hand, the free flow of gases into and out of the alveoli is greater in the upper portions of the lung. This anomaly can also be dealt with by developing the ability to guide the reflexes in the lungs and changing the breathing patterns.
Respiratory control The respiratory mechanism is regulated through nervous and chemical control. The quantity of air inhaled and the Tate of breaths per minute vary considerably, depending on physical, mental and emotional conditions, as well as influences from the external environment.
Respiratory control structure: The respiratory control centre lies in the medulla oblongata at the base of the brain (see figure below). In the medulla there are inspiratory neurones and expiratory neurones. The neurones in the pneumo-taxic and apneustic centres, situated in the pons, influence the inspiratory and expiratory neurones of the medulla. Motor impulses leaving the respiratory centre pass in the phrenic and intercostal nerves to the diaphragm and intercostal muscles respectively, and activate movements in the respiratory muscles to inhale air. Afferent or sensory impulses travel to the medulla via the vagus nerve due to expansion of the alveoli and smaller bronchioles. Central chemo-receptors situated on the surface of the medulla oblongata and peripheral chemo-receptors situated in the arch of
the aorta and in the carotid bodies also respond to changes in the partial pressures of oxygen and carbon dioxide in the blood and cerebrospinal fluid.
All the major structures of the respiratory system have nerves
relating to both the sympathetic BSYO pons
and parasympathetic nervous medulla
systems. Inhalation brings in oblongata
oxygen; it is energizing and
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