H2 receptors are a type of histamine receptor found in various tissues throughout the body. They play a crucial role in regulating gastric acid secretion in the stomach, influencing digestive processes. When activated by histamine, H2 receptors stimulate the parietal cells in the stomach lining to produce more acid, which aids in digestion. In addition to their role in the stomach, H2 receptors are also involved in other physiological functions, such as modulating immune responses and influencing blood vessel dilation. Medications known as H2 antagonists, like ranitidine and famotidine, are commonly used to reduce stomach acid production and treat conditions like gastroesophageal reflux disease (GERD).