The
chemoreceptor trigger zone (
CTZ) is an area of the
medullaThe medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
which receives inputs from
bloodBlood is a specialized bodily fluid that delivers necessary substances to the body's cells — such as nutrients and oxygen — and transports waste products away from those same cells....
-borne
drugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
s or
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
s, and communicates with the vomiting center, to initiate
vomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Undesired vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure...
. The CTZ is close to the
area postremaThe area postrema is a part of the brain that controls vomiting. It was discovered in 1953 by Utah Pharmacologists Herbert L. Borison and S. C. Wang .-Location:It is located in the lateral reticular formation of the medulla oblongata...
on the floor of the
fourth ventricleThe fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
and is outside of the
blood-brain barrierThe blood-brain barrier is a separation of circulating blood and cerebrospinal fluid maintained by the choroid plexus in the central nervous system . Endothelial cells restrict the diffusion of microscopic objects The blood-brain barrier (BBB) is a separation of circulating blood and...
. The
neurotransmitterNeurotransmitters are endogenous chemicals which relay, amplify, and modulate signals between a neuron and another cell. Neurotransmitters are packaged into synaptic vesicles that cluster beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they...
s implicated in the control of
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
and vomiting include
acetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system and the only neurotransmitter used in the motor division...
,
dopamineDopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D
1, D
2, D
3, D
4, and...
,
histamineHistamine is a biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by basophils and by...
(H-1 receptor),
substance PIn the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...
(NK-1 receptor), and 5-HT (5-HT3 receptor). There are also
opioid receptorOpioid receptors are a group of G-protein coupled receptors with opioids as ligands. The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nociceptin...
s present which may be the mechanism by which
opiateIn medicine, the term opiate describes any of the narcotic opioid alkaloids found as natural products in the opium poppy plant, as well as many semisynthetic chemical derivatives of such alkaloids.-Overview:...
s cause nausea and vomiting.
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The
chemoreceptor trigger zone (
CTZ) is an area of the
medullaThe medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
which receives inputs from
bloodBlood is a specialized bodily fluid that delivers necessary substances to the body's cells — such as nutrients and oxygen — and transports waste products away from those same cells....
-borne
drugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
s or
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
s, and communicates with the vomiting center, to initiate
vomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Undesired vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure...
. The CTZ is close to the
area postremaThe area postrema is a part of the brain that controls vomiting. It was discovered in 1953 by Utah Pharmacologists Herbert L. Borison and S. C. Wang .-Location:It is located in the lateral reticular formation of the medulla oblongata...
on the floor of the
fourth ventricleThe fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
and is outside of the
blood-brain barrierThe blood-brain barrier is a separation of circulating blood and cerebrospinal fluid maintained by the choroid plexus in the central nervous system . Endothelial cells restrict the diffusion of microscopic objects The blood-brain barrier (BBB) is a separation of circulating blood and...
. The
neurotransmitterNeurotransmitters are endogenous chemicals which relay, amplify, and modulate signals between a neuron and another cell. Neurotransmitters are packaged into synaptic vesicles that cluster beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they...
s implicated in the control of
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
and vomiting include
acetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system and the only neurotransmitter used in the motor division...
,
dopamineDopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D
1, D
2, D
3, D
4, and...
,
histamineHistamine is a biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by basophils and by...
(H-1 receptor),
substance PIn the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...
(NK-1 receptor), and 5-HT (5-HT3 receptor). There are also
opioid receptorOpioid receptors are a group of G-protein coupled receptors with opioids as ligands. The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nociceptin...
s present which may be the mechanism by which
opiateIn medicine, the term opiate describes any of the narcotic opioid alkaloids found as natural products in the opium poppy plant, as well as many semisynthetic chemical derivatives of such alkaloids.-Overview:...
s cause nausea and vomiting.