The vomiting center is composed of the area postrema and the nucleus solitarius and is located in the brainstem. It triggers the process of vomiting in a defensive response to potential toxins that a person ingests through food. Cerebral vomiting is based on increased intracranial pressure or direct pressure on the vomiting center; possible causes include traumatic brain injury, stroke, cerebral edema, tumors, heat stroke or sunstroke, and other medical conditions.
What is the vomiting center?
The vomiting center is a part of the brain and is located in the brain stem. It owes its name to its main function: triggering vomiting and coordinating different areas of the brain that are involved in it. Exactly how the individual parts of the vomiting center interact is not yet fully understood. The most important structures of the vomiting center are the area postrema and the nocleus solitarius; however, it also has numerous connections to other parts of the brain and forms a complex network of neurons.
Anatomy and structure
Anatomically, the vomiting center does not form a self-contained structure; instead, it represents an association of nerve cells that have particularly good connections within a network. Nevertheless, medicine refers to it as a “center” because the vomiting center forms a functional unit. Two anatomical structures form its physiological basis: the area postrema and the nucleus solitarius (also known as nucleus tractus solitarii or NTS for short), which in turn both belong to the formatio reticularis. This lies mostly in the brainstem, but has extensions into the medulla oblongata (medulla oblongata) and diencephalon (diencephalon). Within this area, the nucleus solitarius is located at the rhomboid fossa. The area postrema lies dorsal from the nucleus solitarius, i.e., toward the back. It includes, among other things, the chemoreceptor trigger zone, a network of specialized neurons located anterior to the blood-brain barrier. In addition, the vomiting center receives information from other nerve groups; for example, those that process stimuli from the gastrointestinal tract.
Function and tasks
The vomiting center is responsible for controlling vomiting. As part of the area postrema, the chemoreceptor trigger zone lies anterior to the blood-brain barrier and exerts a protective function: The neurons of this area have receptors that are sensitive to certain chemical substances – especially to various toxins. When such a substance binds to a receptor, it triggers a biochemical reaction in the nerve cell. As soon as this exceeds the critical threshold, the neuron triggers an electrical signal and transmits it via the area postrema. In this way, the chemoreceptor trigger zone detects toxins before they can spread through the blood vessels of the brain. The vomiting center responds to this stimulus by causing the affected person to vomit. Ideally, the body gets rid of a large part of the toxic substances in this way, even before they can enter the bloodstream. A link to the sense of balance can cause vomiting as a result of rapid spinning or roller coaster riding. The other important part of the vomiting center, the nucleus solitarius, is not only involved in vomiting, but also represents the taste nucleus of the brain. It performs important preliminary work in filtering and processing information that leads to subjective taste perception in higher sensory centers. Its tasks therefore go far beyond the functions it performs in the context of the vomiting center. When the nucleus solitarius finds a taste stimulus indicative of toxic food, the vomiting center also responds. Disgust represents a subjective response to repulsive stimuli; the vomiting center also plays a role. However, the psychic feeling itself does not form in the vomiting center, and it does not represent a purely physical sensation. Instead, it develops in the cerebrum, where higher cognitive processes also influence the disgust sensation. Interpretations of disgust by the cerebrum can in turn influence physiological nausea; however, this requires very strong sensations.
Diseases
Physicians refer to cerebral vomiting when there is no physiologic stimulus, such as toxins, but a patient vomits because of inadequate stimulation of the vomiting center.In this case, the vomiting center does not actually receive a stimulus from outside; instead, a false stimulus triggers the electrical potential in the nerve cells. The brain cannot recognize the difference and therefore treats the signal in the same way as a real sensory impression. False stimulation can result, for example, from increased intracranial pressure. Possible causes are severe injuries, tumors, cerebral edema (due to drainage disorders, heat stroke or sunstroke, etc. ), circulatory disorders of the brain or a stroke. A stroke interrupts the blood supply to the brain, so that the nerve cells no longer receive sufficient oxygen. This causes both temporary neurological symptoms and permanent failures of brain areas where nerve cells have already died during the undersupply. In addition, direct pressure on the vomiting center can trigger cerebral vomiting. This is the case, for example, if a tumor develops near the vomiting center or if there is a traumatic brain injury. The mildest form of traumatic brain injury is concussion; if it causes unconsciousness, it lasts no longer than ten minutes. Doctors treat cerebral vomiting on the one hand by treating its cause, and on the other hand also symptomatically with various medications. Antagonists of the neurotransmitters serotonin, dopamine, and tachykinin are considered for drug treatment.
