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neurotoxin
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What is a neurotoxin?
A neurotoxin is any substance that can disrupt the nervous system's structure or function. These substances can be natural or synthetic, and can enter the body through inhalation, ingestion, skin contact, or injection.
Neurotoxins can either be of external origin, entering the body from environmental sources, or endogenous, being produced and existing within the body. They can cause neurons to malfunction or disrupt communication between neurons, with impacts that range from temporary to permanent. Exposure to neurotoxins can lead to a variety of issues, including cognitive and behavioral problems.
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How do neurotoxins affect the nervous system?
Neurotoxins are substances that disrupt the nervous system's structure or function. These can be natural or synthetic compounds like snake venom, pesticides, alcohol, or cocaine.
Neurotoxins can enter the body through inhalation, ingestion, skin contact, or injection, leading to immediate or long-term effects. They cause neurons to malfunction or disrupt communication between them. For example, botulinum toxin blocks the release of acetylcholine, a neurotransmitter needed for muscle contraction, resulting in paralysis.
Exposure to neurotoxins can result in temporary effects such as slurred speech or permanent damage like cognitive impairment. Factors such as age, health, and level of exposure determine the severity of the neurotoxin's impact.
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Where can neurotoxins be found in nature?
Neurotoxins, substances that disrupt the nervous system's structure or function, are found in various natural sources. Many animals, like snakes, bees, and spiders, use neurotoxins as weapons. Certain wasps utilize them to paralyze prey for later consumption.
Clostridium species, bacteria present in the soil, produce neurotoxins that can enter the body through contaminated food or puncture wounds. Some plants also contain phytotoxins, such as alkaloids, that are poisonous if eaten.
However, neurotoxins are not always external; the body can also produce them. For example, nitric oxide and glutamate act as neurotransmitters but can become toxic to neurons at high concentrations.
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What are some examples of animals that produce neurotoxins?
Neurotoxins, substances that disrupt the nervous system's structure or function, are produced by various animals as venom for predation or defense.
Examples include:
* Snakes Cobras and coral snakes use neurotoxic venom to paralyze prey.
* Scorpions Their stings contain neurotoxins that can cause severe symptoms, including respiratory distress and muscular twitching.
* Spiders Black widow spiders inject a neurotoxic venom that causes intense cramping pain and muscle rigidity.
* Bees Honeybee venom contains neurotoxins, among other substances, that cause acute pain and can be lethal in high doses.
* Marine Animals Certain fish, such as soapfish, produce neurotoxic slime. Some cone snails use venom containing quaternary ammonium compounds to immobilize prey.
* Lizards Gila monsters possess venom primarily composed of neurotoxins.4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do neurotoxins cause harm to humans or other animals?
Neurotoxins are poisonous substances that disrupt the normal function of nerve cells in the nervous system. These substances can be natural or human-made chemical compounds, such as snake venom, pesticides, ethyl alcohol, heroin, and cocaine.
Neurotoxins can enter the body through inhalation, ingestion, skin contact, or injection, affecting nerve function depending on the substance's toxicity, the individual's health, and the level and frequency of exposure. They can cause neurons to malfunction or disrupt communication between neurons. For example, botulinum toxin blocks the release of acetylcholine, a neurotransmitter needed for muscle contraction, leading to paralysis. The effects can be immediate and temporary, like slurred speech from alcohol, or long-lasting and irreversible, like cognitive damage from lead exposure.
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How are neurotoxins used in medicine or research?
Neurotoxins, substances that disrupt the nervous system's structure or function, have varied applications in medicine and research.
In controlled doses, botulinum toxin can relax muscles, leading to the drug Botox. Botox helps manage neurological conditions by controlling involuntary spastic movements from abnormal muscle contractions, such as those seen in cervical dystonia and cerebral palsy. It also treats overactive bladders and reduces facial wrinkles.
Scientists also use neurotoxins to study the nervous system. For example, observing the effects of axonal destruction or using retrograde axonal flow techniques help demonstrate the origin of fiber tracts.
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neurotoxin, substance that alters the structure or function of the nervous system. More than 1,000 chemicals are known to have neurotoxic effects in animals. The substances include a wide range of natural and human-made chemical compounds, from snake venom and pesticides to ethyl alcohol, heroin, and cocaine.
Characteristics
Many neurotoxins are of external origin, entering the body from environmental sources. Others, however, are endogenous, being produced and existing within the body. Examples of endogenous neurotoxins include the neurotransmitters nitric oxide and glutamate. Although both are important to cell communication in the nervous system, they can become toxic to neurons in high concentrations.
The extent to which a neurotoxin affects nerve function depends on the toxicity of the substance and on the individual’s age and health (particularly renal and hepatic health) at the time of exposure. It also depends on the level and frequency of contact with a chemical; the same substance can have both toxic and therapeutic effects at different concentration levels. For instance, vitamin A and vitamin B6 are vital to a healthy diet; however, they become neurotoxic in large doses. Some puffer fish (and certain other aquatic and terrestrial animals) carry tetrodotoxin, an extremely potent inhibitor of voltage-gated sodium channels on neurons; nonetheless, fugu, a dish prepared from puffer species, is a traditional culinary delicacy in Japan. When inhaled, less than one microgram of botulinum toxin, a protein produced by the bacterium Clostridium botulinum, is lethal to humans; the toxin, in the form of Botox, however, is also used for a variety of medicinal and cosmetic purposes. Likewise, life-saving chemotherapy treatment and antipsychotic drugs can also have neurotoxic effects, although the benefits often outweigh the risks.
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Physiological effects
Neurotoxins are absorbed through inhalation, ingestion, skin contact, or injection and can have immediate or long-lasting impacts by causing neurons to malfunction or by disrupting interneuron communication. Slurred words or poor coordination due to toxic effects on neurons from alcohol consumption, for example, are temporary, whereas cognitive damage caused by lead exposure is irreversible. Certain neurotoxins are highly potent and have been developed into chemical weapons. The nerve agent sarin, for example, is an organophosphorous compound that is classified as a weapon of mass destruction; sarin gas can kill a person within 10 minutes of exposure.
Young and elderly persons are particularly vulnerable to neurotoxic chemicals. In elderly individuals, a decline in neural function associated with aging can limit the ability to cope with the effects of neurotoxins, particularly for those with compromised liver metabolism or impaired renal function, which are the primary routes of toxin clearance from the body. Prenatal, postnatal, and early childhood exposure to certain chemicals can result in permanent damage to the developing brain, causing functional deficits that become apparent immediately or that emerge later in life. Studies have shown that the placenta cannot prevent many toxins from passing from mother to fetus; moreover, chemicals can be transferred through breast milk.
Certain chemicals found in the environment and in common household items have been linked to behavioral and cognitive problems in children. In the early 2000s, increased exposure to some of those chemicals during fetal and early childhood development—as result of overall increases in the use of chemicals in food production and in consumer products—was blamed for the sharp rise in disorders such as autism and attention-deficit/hyperactivity disorder (ADHD) in children. Although genetic factors play a role, neurotoxins such as arsenic, chlorpyrifos, DDT (dichlorodiphenyltrichloroethane), ethyl alcohol, fluoride, lead, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), manganese, mercury, and toluene are major contributors to the prevalence of neurobehavioral disorders.
The impact of some neurotoxins, such as lead and ethyl alcohol, are well-documented. Fetal alcohol syndrome, characterized by brain damage and developmental delays in children, has been known since the 1970s to occur in children born to alcoholic mothers. Concern about lead contamination dates to ancient Rome, where the malleable metal was used to line aqueducts. Roman author and civil engineer Vitruvius noted that “in casting lead, the fumes from it…destroy the vigour of the blood.”
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In the modern era, there is significant concern about the combined effects of moderate and even low-level exposure to multiple neurotoxins; more research is needed, however, to determine the physiological significance of such exposures. In addition, thousands of other chemicals are suspected of having neurotoxic effects, though many remain untested.