Vomiting Reflex - Essay Example

Vomiting Reflex Vomiting, also known as emesis is a manifestation of a wide variety of conditions including vestibular dysfunction, gastrointestinal conditions, adverse effects from medication and systemic disorders or infections. The vomiting centre is a region in the medulla that coordinates the act of vomiting through the cranial nerves, parasympathetic and sympathetic nervous outflow (John, 2010). In addition, the vomiting centre receives afferent input from the chemotrigger zone, also known as the area postrema.

The Chemotrigger Zone (CTZ) is located at the 4th ventricle outside the blood brain barrier. This means that it can receive direct emetogenic stimulation from the cerebrospinal fluid and blood. The CTZ sends impulses to the vomiting impulses to the vomiting centre. The process of vomiting includes the retching and the expulsive phase. In the retching phase, the vomiting centre transmits motor efferent impulses to the abdominal muscles and the diaphragm resulting in increased intra-abdominal pressure.

It also results in anti-peristalsis forces that can go all the way to the duodenum and ileum. Gastric content accumulates in the stomach resulting in relaxation of the lower esophageal sphincter (John, 2010). This is accompanied by hypersalivation, increased heart rate and sweating through the parasympathetic outflow. The hyoid bone and the larynx are elevated so as to open the upper esophageal sphincter. This is followed by the closure of the glottis. The increased intra-abdominal pressure and anti-peristalsis forces results in the expulsion of the abdominal contents.

The following is a flow chart demonstrating the vomiting reflex. Motor and Parasympathetic efferent activity The contents and color of the vomitus may be used to diagnosis the cause of vomiting. Bleeding from the esophagus is showed by the presence of fresh blood in the vomitus. When the blood originates from the stomach, for example, perforated peptic ulcer, the vomitus has coffee ground appearance.

This is because the acid found in the stomach reacts with the iron found in hemoglobin. Presence of bile in the vomitus indicates that the pyloric valve is open. This means that there is massive contraction of the duodenum leading to expulsion of bile (John, 2010). Fecal content in the vomitus indicates a gastrocolic fistula or intestinal obstruction. In case of intestinal obstruction, the vomiting relieves the associated abdominal pain and distension. These features are used to determine the origin of pathology in the gastrointestinal tract.

Reference ListJohn, T. (2010). Guyton and Hall Textbook of Medical Physiology. NY: Saunders.