Nausea and vomiting are common symptoms that are associated with a variety of conditions (Mayo Clinic 2020).
What are Nausea and Vomiting?
It is important to note that nausea and vomiting are not conditions themselves - rather, they are non-specific symptoms (Cleveland Clinic 2019).
Nausea describes a feeling of unease in the stomach, chest or throat. Someone experiencing nausea will usually feel the urge to vomit, but vomiting will not necessarily occur.
Vomiting (emesis) is the physical act of forcibly ejecting stomach contents through the mouth. This may be a voluntary or involuntary action. Vomiting may occur independently of nausea.
(Cleveland Clinic 2019; Encyclopedia Britannica 2017; Shiel 2020)
Vomiting is a protective mechanism used to expel harmful substances in the stomach. It may also occur in response to irritation in the gut (NHS Inform 2020).
While nausea and vomiting may indicate a serious condition, they are not usually a cause for concern and generally resolve after one to two days (NHS Inform 2020).
Symptoms that are often associated with nausea and vomiting include:
Acute nausea and vomiting generally describes symptoms that resolve within 48 hours. Nausea and vomiting that persists for over 48 hours may lead to complications or indicate a more serious illness (Knott 2020).
The Physiology of Vomiting
There are several sites involved in nausea and vomiting, in particular:
The chemoreceptor trigger zone (CTZ) , which is located in the brain near the vomiting centre in the medulla
The gastrointestinal tract
The vestibular system, which is responsible for balance, spatial orientation and movement
The higher centres in the cortex and thalamus.
(Athavale, Athavale & Roberts 2020; MacDougall & Sharma 2020)
These sites relay information to the vomiting centre, which is located in the medulla oblongata (part of the brain stem) and receives input from the nucleus tractus solitarius and vagus nerve. The vomiting centre is in charge of causing the vomiting reflex (MacDougall & Sharma 2020; Athavale, Athavale & Roberts 2020).
There are specific neurotransmitters that induce the action of vomiting. These include histamine, dopamine, serotonin, acetylcholine and neurokinin (Athavale, Athavale & Roberts 2020).
Prior to vomiting, the individual may display:
Increased heart rate
Increased saliva production (to protect the teeth from stomach acid).
(Queensland Health 2018)
During the vomiting process, muscles in the diaphragm, chest wall and abdomen begin to contract, forcing the stomach contents upward. While this occurs, the epiglottis closes to ensure that the stomach contents cannot enter the trachea or lungs (Queensland Health 2018).
Causes of Nausea and Vomiting
There are many potential causes of nausea and vomiting, including: