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21 - travel through reticulospinal tract in the spinal cord...

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2. REGULATION AND CONTROL OF BREATHING: In order to maintain normal levels of partial oxygen and carbon dioxide pressure both the depth and rate of breathing are precisely regulated. Basic elements of the respiratory control system are (1) strategically placed sensors (2) central controller (3) respiratory muscles. 7 CENTRAL CONTROLLER: Breathing is mainly controlled at the level of brainstem. The normal automatic and periodic nature of breathing is triggered and controlled by the respiratory centres located in the pons and medulla. These centres are not located in a special nucleus or a group of nuclei but they are rather poor defined collection of neurones. 1. Medullary respiratory centre: - Dorsal medullary respiratory neurones are associated with inspiration: It has been proposed that spontaneous intrinsic periodic firing of these neurones responsible for the basic rhythm of breathing. As a result, these neurones exhibit a cycle of activity that arises spontaneously every few seconds and establish the basic rhythm of the respiration. When the neurones are active their action potentials
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Unformatted text preview: travel through reticulospinal tract in the spinal cord and phrenic and intercostal nerves and finally stimulate the respiratory muscles.-Ventral medullary respiratory neurones are associated with expiration. These neurones are silent during quite breathing because expiration is a passive event following an active inspiration. However, they are activated during forced expiration when the rate and the depth of the respiration is increased e.g. exercise. During heavy breathing increased activity of the inspiratory centre neurones activates the expiratory system. In turn, the increased activity of the expiratory system inhibits the inspiratory centre and stimulates muscles of expiration. The dorsal and ventral groups are bilaterally paired and there is cross communication between them. As a consequence they behave in synchrony and the respiratory movements are symmetric....
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