Pathophysiological causes * Swallowing air excessively * Gastroesophageal reflux * Hiatal hernia * Rapid eating * Carbonated beverages, alcohol, dry breads, and some spicy foods * Opiate drug use * Laughing vigorously or for a long time<unk> s may be triggered by a number of common human conditions. In rare cases, they can be a sign of serious medical problems. In rare cases<unk> s can be the sole symptom of myocardial infarction. Pre-phrenic nucleus irritation of medulla * Kidney failure CNS disorders * Stroke * Multiple sclerosis * Meningitis Nerve damage * Damage to the vagus nerve after surgery Other known associations * Although no clear pathophysiological mechanism has been described,<unk> s is known to have been the initial symptom of Plasmodium vivax malaria in at least one documented case. Evolutionary theories The burping reflex hypothesis A leading hypothesis is that<unk> s evolved to facilitate greater milk consumption in young mammals. The coordination of breathing and swallowing during suckling is a complicated process. Some air inevitably enters the stomach, occupying space that could otherwise be optimally used for calorie rich milk. The hypothesis suggests that the presence of an air bubble in the stomach stimulates the sensory (afferent) limb of the reflex through receptors in the stomach, esophagus and along the underside of the diaphragm. This triggers the active part of the<unk>  (efferent limb), sharply contracting the muscles of breathing and relaxing the muscles of the esophagus, then closing the vocal cords to prevent air from entering the lungs. This creates suction in the chest, pulling air from the stomach up into the esophagus. As the respiratory muscles relax the air is expelled through the mouth, effectively “burping” the animal. There are a number of characteristics of<unk> s that support this theory. The burping of a suckling infant may increase its capacity for milk by more than 15-25%, bringing a significant survival advantage. There is a strong tendency for infants to get<unk> s, and although the reflex persists throughout life it decreases in frequency with age. The location of the sensory nerves that trigger the reflex suggests it is a response to a condition in the stomach. The component of the reflex that suppresses peristalsis in the esophagus while the airway is being actively blocked suggests the esophagus is involved. Additionally,<unk> s are only described in mammals - the group of animals that share the trait of suckling their young. Phylogenetic hypothesis An international respiratory research group composed of members from Canada, France, and Japan proposed that the<unk>  is an evolutionary remnant of earlier amphibian respiration. Amphibians such as tadpoles gulp air and water across their gills via a rather simple motor reflex akin to mammalian<unk> ing. The motor pathways that enable<unk> ing form early during fetal development, before the motor pathways that enable normal lung ventilation form. Thus, the<unk>  is evolutionarily antecedent to modern lung respiration. Additionally, this group (C. Straus et al.) points out that<unk> s and amphibian gulping are inhibited by elevated CO2 and may be stopped by GABAB receptor agonists, illustrating a possible shared physiology and evolutionary heritage. These proposals may explain why premature infants spend 2.5% of their time<unk> ing, possibly gulping like amphibians, as their lungs are not yet fully formed. The phylogenetic hypothesis may explain<unk> s as an evolutionary remnant, held over from our amphibious ancestors. This hypothesis has been questioned because of the complexity of the mammalian<unk>  reflex compared to the amphibian breathing reflex, the fact that it does not explain the reason for glottic closure, and because the very short contraction of the<unk>  is unlikely to have a significant strengthening effect on the slow-twitch muscles of respiration. Fetal intrauterine<unk> s are of two types. The physiological type occurs prior to twenty-eight weeks after conception and tends to last five to ten minutes. These<unk> s are part of fetal development and are associated with the myelination of the phrenic nerve, which primarily controls the thoracic diaphragm. The phylogenetic and the burping hypotheses are not mutually exclusive. The phylogeny hypothesis could explain how the<unk>  reflex might have evolved, while the “Burping Hypothesis” could explain why it would offer enough of an evolutionary advantage to persist and increase in complexity.
Hiccup
Sleepwalking
Drooling
Hypersomnia
Stuttering
Snatiation
Orthosomnia
Kussmaul breathing