Receptors Cough ... Group 5 swim or sink

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The cough reflex arc is complex . Controlled by its nerve center in the medulla, the reflex arc is served by afferent fibers of the vagus, trigeminal, glossopharyngeal, and phrenic nerves.Stimuli to tissue innervated by these nerves may precipitate the cough response.

Cough receptors are located in the bronchi, diaphragm, external auditory canal, larynx, nose, paranasal sinuses , pericardium, pharynx, pleura, stomach, trachea and tympanic membrane. The efferent pathway of this arc stems from the medullary center through the vagus, phrenic, and spinal motor nerves, which innervate the intrinsic and accessory muscles of respiration.

The act of coughing involves synchronous participation of a number of muscles during the inspiratory and expiratory phases. During inspiration, the glottis opens, bronchioles enlarge, and lungs expand with the help of the diaphragm and the thoracic and abdominal muscles. Thus, the lungs are stretched and ready for recoil. The glottis closes at the height of inspiration, and the chest contracts with inspiration, thereby increasing the intrathoracic pressure to well over 100 mm Hg. Consequently, when the glottis gives way and opens, the rate of air flow is as high as 600 L/min,or up to 500 miles/hr. Even though the common cold and most infectious causes of tracheobronchiti are short-lived , cough may linger for 1 to 3 weeks because of simple epithelial damage or overt bronchial hyperactivity . Frequent, paroxysmal coughing is particularly distressing to patients and others in their environment and disrupts work and sleep.


References
1/ http://www.medstudents.com.br/pneumo/pneumo3.htm
2/ Harrison's Internal Medicine 17th > Chapter 34. Cough and Hemoptysis

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