If a person is suffering from gerd, the is malfunctioning.

esophageal sphincter

Explanation:

Gastroesophageal reflux disease (GERD) is one of the most important digestive disorders given the high and increasing incidence, the intensity of the symptoms and the severity of the complications. Is defined as a condition that matters when the reflux of gastric contents causes symptoms and complications.  Heartburn, or pyrosis, is a backward burning sensation and that can be felt up to the cervical region. The most common triggering aliments are greasy or spicy foods, citrus fruits, carminatives, coffee, soft drinks, alcohol, large meals, tobacco, medicines and bedtime immediately after meals.  The factors of relief are ingestion of milk, water or antacids.

answer; a muscle cell, another neuron and a of the above