Swallowing reflex
Swallowing centre is located in the brain stem (medulla oblongata). Stimulation of the receptors in the soft palate, pharynx (posterior wall) and epiglottis (dorsal surface) by food material initiate this reflex.
It is a complex multi synaptic reflex involving pharyngeal and oesophageal stage.
Sensory fibres pass through trigeminal, glossopharyngeal and vagus nerve.
This reflex involves internuncial neurons.
Efferent fibres emerge through glossopharyngeal, vagus and hypoglossal nerves which supply to the muscles of myohyoid and hypoglossal.
The muscles press the tounge against hard palate.
This causes the tounge to draw backward with the elevation of soft palate.
Now the tounge forces the bolus into opened oesophagus.
Opening of the oesophagus is by the pulling action of hyoid bone and layrnx.
As it happens the epiglottis closes so as to shut the layrnx.
Swallowing centre also activate through its efferent limb the neighbouring neurons that control respiration.
This interupts respiration during swallowing as a preventive measure to avoid aspiration of food particles into respiratory passage.