This cookie is set by GDPR Cookie Consent plugin. These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. There is expiration against the closed epiglottis, causing a further increase in intra-thoracic pressure. The epiglottis and vocal cords close, trapping the air within the lungs. The external intercostal muscles and diaphragm then contract causing expansion of the chest cavity, facilitating movement of air into the lungs, and increasing intra-thoracic pressure. Irritation of cough receptors causes the vocal cords to open more widely, allowing more air to enter the lungs. There are three main phases to the cough reflex: Inspiratory Phase This article will discuss the cough reflex arc, its phases and clinical correlations. The cough reflex is an important defence mechanism which clears the airways of irritants by forcefully expelling air from the respiratory tract. Rectus abdominis contracts to depress the rib cage and decrease space in the thoracic cavity.The external intercostal muscles contract to change the space available in the thoracic cavity.The laryngeal muscles contract to close the vocal cords.The diaphragm contracts to become flattened which increases the thoracic cavity space.Various respiratory muscles contract to allow initiation of the cough reflex. The vagus nerve then synapses with motor neurones, delivering information to effector muscles which triggers the cough reflex to occur. Sensory information travels to the nucleus tractus solitarius (NTS) of the medulla. Sensory information travels from these fibres through the afferent pathway via the vagus nerve to the medulla oblongata. These are non-myelinated nerve fibres which respond to mechanical and chemical stimuli.These are myelinated fibres which respond more slowly to mechanical stimuli and are involved in the Hering-Breuer reflex.Slowly Adapting Stretch Receptors (SARs).These are myelinated fibres found mostly in the pharynx and trachea which rapidly respond to mechanical stimuli, e.g.Rapidly Adapting Stretch Receptors (RARs).There are three main types of sensory nerve fibres involved in the afferent pathway: Irritants are detected by these receptors and they send sensory information to afferent nerves. The cough reflex arc is initiated by irritation of cough receptors, for example, mechanoreceptors or chemoreceptors. The cough reflex arc is made up of three main pathways: Sensory Afferent Pathway
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