Lindhurst High School is located in Olivehurst, California , USA. It is one of two high schools in the Marysville Joint Unified School District of Yuba County and draws students from the communities of Olivehurst , Linda , Plumas Lake , and Marysville .
123-488: On May 1, 1992, the school saw a school shooting and subsequent siege. The gunman, 20-year-old Eric Houston, was a former student at Lindhurst High School. Houston killed three students and one teacher and wounded nine students and a teacher before surrendering to police. Houston was sentenced to death for the murders, and he is currently on California 's death row in San Quentin State Prison . It, along with
246-469: A myelinated axon , which are found periodically interspersed between segments of the myelin sheath. Therefore, at the point of the node of Ranvier, the axon is reduced in diameter. These nodes are areas where action potentials can be generated. In saltatory conduction , electrical currents produced at each node of Ranvier are conducted with little attenuation to the next node in line, where they remain strong enough to generate another action potential. Thus in
369-444: A bullying-school shootings connection. The Uvalde shooter who killed 21 people was frequently bullied in 4th grade at Robb Elementary school. The degree to which mental illness contributes to school shootings has been debated. Although the vast majority of mentally ill individuals are non-violent, some evidence has suggested that mental illness or mental health symptoms are nearly universal among school shooters. A 2002 report by
492-483: A guide for helping to identify potential school shooters, The School Shooter: A Threat Assessment Perspective . Daniel Schechter , Clinical Psychiatrist, wrote that for a baby to develop into a troubled adolescent who then turns lethally violent, a convergence of multiple interacting factors must occur, that is "every bit as complicated...as it is for a tornado to form on a beautiful spring day in Kansas". Thus, reinforcing
615-429: A healthy social life . Some, such as Alan Lipman , have warned about the lack of empirical validity of profiling methods. According to Raine (2002), immaturity is one of many identified factors increasing the likelihood of an individual committing criminal acts of violence and outbursts of aggression . This fact is supported by findings on brain development occurring as individuals age from birth. According to
738-482: A myelinated axon, action potentials effectively "jump" from node to node, bypassing the myelinated stretches in between, resulting in a propagation speed much faster than even the fastest unmyelinated axon can sustain. An axon can divide into many branches called telodendria (Greek for 'end of tree'). At the end of each telodendron is an axon terminal (also called a terminal bouton or synaptic bouton, or end-foot ). Axon terminals contain synaptic vesicles that store
861-425: A nerve in the peripheral nervous system can be described as neurapraxia , axonotmesis , or neurotmesis . Concussion is considered a mild form of diffuse axonal injury . Axonal injury can also cause central chromatolysis . The dysfunction of axons in the nervous system is one of the major causes of many inherited and acquired neurological disorders that affect both peripheral and central neurons. When an axon
984-514: A neurite, causing it to elongate, will make it become an axon. Nonetheless, axonal development is achieved through a complex interplay between extracellular signaling, intracellular signaling and cytoskeletal dynamics. The extracellular signals that propagate through the extracellular matrix surrounding neurons play a prominent role in axonal development. These signaling molecules include proteins, neurotrophic factors , and extracellular matrix and adhesion molecules. Netrin (also known as UNC-6)
1107-505: A neurite, converting it into an axon. As such, the overexpression of phosphatases that dephosphorylate PtdIns leads into the failure of polarization. The neurite with the lowest actin filament content will become the axon. PGMS concentration and f-actin content are inversely correlated; when PGMS becomes enriched at the tip of a neurite, its f-actin content is substantially decreased. In addition, exposure to actin-depolimerizing drugs and toxin B (which inactivates Rho-signaling ) causes
1230-502: A peer-reviewed journal article on the subject. It also quotes Gary Noesner, who helped create and lead the FBI's hostage negotiation unit, and served as Chief Negotiator for ten years. It has long been debated whether there exists a correlation between school shooting perpetrators and the type of media they consume. A popular profile for school shooters is someone who has been exposed to or enjoys playing violent video games. However, this profile
1353-490: A political debate over gun violence , zero tolerance policies, gun rights and gun control . According to studies, factors behind school shooting include easy access to firearms, family dysfunction, lack of family supervision, and mental illness among many other psychological issues. Among the topmost motives of attackers were: bullying/persecution/threatened (75%) and revenge (61%), while 54% reported having numerous reasons. The remaining motives included an attempt to solve
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#17329098982561476-403: A presynaptic terminal, it activates the synaptic transmission process. The first step is rapid opening of calcium ion channels in the membrane of the axon, allowing calcium ions to flow inward across the membrane. The resulting increase in intracellular calcium concentration causes synaptic vesicles (tiny containers enclosed by a lipid membrane) filled with a neurotransmitter chemical to fuse with
1599-542: A primary school, secondary school, high school or university, involving the use of a firearm . Many school shootings are also categorized as mass shootings due to multiple casualties. The phenomenon is most widespread in the United States , which has the highest number of school-related shootings, although school shootings take place elsewhere in the world. Especially in the United States, school shootings have sparked
1722-608: A problem (34%), suicide or depression (27%), and seeking attention or recognition (24%). The United States Secret Service published the results from a study regarding 37 school shooting incidents, involving 41 individuals in the United States from December 1974 through May 2000. In a previous report of 18 school shootings by the Federal Bureau of Investigation (FBI), they released a profile that described shooters as middle-class, lonely/alienated, awkward, Caucasian males who had access to guns. The most recent report cautioned against
1845-554: A secreted protein, functions in axon formation. When the UNC-5 netrin receptor is mutated, several neurites are irregularly projected out of neurons and finally a single axon is extended anteriorly. The neurotrophic factors – nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NTF3) are also involved in axon development and bind to Trk receptors . The ganglioside -converting enzyme plasma membrane ganglioside sialidase (PMGS), which
1968-402: A tendency to blame others for problems. However, they note that attempting to "profile" school shooters with such a constellation of traits will likely result in many false positives as many individuals with such a profile do not engage in violent behaviors. McGinty and colleagues conducted a study to find out if people tended to associate the violence of school shootings with mental illness, at
2091-418: A victim again and try to regain their image by joining groups. Often, they are rejected by their peers and follow through by restoring justice in what they see as an unjust situation. Their plan for restoration many times results in violence as shown by the school shooters. 75% of school shooters had been bullied or left behind evidence of having been victims of bullying . Other academics however are critical of
2214-469: Is blocked and neutralized, it is possible to induce long-distance axonal regeneration which leads to enhancement of functional recovery in rats and mouse spinal cord. This has yet to be done on humans. A recent study has also found that macrophages activated through a specific inflammatory pathway activated by the Dectin-1 receptor are capable of promoting axon recovery, also however causing neurotoxicity in
2337-488: Is close to 1 millimeter in diameter, the size of a small pencil lead. The numbers of axonal telodendria (the branching structures at the end of the axon) can also differ from one nerve fiber to the next. Axons in the central nervous system (CNS) typically show multiple telodendria, with many synaptic end points. In comparison, the cerebellar granule cell axon is characterized by a single T-shaped branch node from which two parallel fibers extend. Elaborate branching allows for
2460-489: Is common in schools and seemed to play a role in the lives of many of the school shooters". A typical bullying interaction consists of three parts, the offender/bully, a victim, and one or more bystanders. This formula of three enables the bully to easily create public humiliation for their victim. Students who are bullied tend to develop behavioral problems, depression, less self-control and poorer social skills, and to do worse in school. Once humiliated, victims never want to be
2583-446: Is considered by many researchers to be misguided or erroneous. Ferguson (2009) has argued that a third variable of gender explains the illusory correlation between video game use and the type of people who conduct school shootings. Ferguson explains that the majority of school shooters are young males, who are considerably more aggressive than the rest of the population. A majority of gamers are also young males. Thus, it appears likely that
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#17329098982562706-430: Is crushed, an active process of axonal degeneration takes place at the part of the axon furthest from the cell body. This degeneration takes place quickly following the injury, with the part of the axon being sealed off at the membranes and broken down by macrophages. This is known as Wallerian degeneration . Dying back of an axon can also take place in many neurodegenerative diseases , particularly when axonal transport
2829-565: Is disproportionately high for prisoners (30–50%), however, it is also disproportionately high for high-performing scientists (26%) and US presidents (34%). Harvard's Baker Foundation Professor Emerita Dr. Teresa M. Amabile states, "Those kinds of events can crush a child, they can lead to a lot of problems; they can lead to substance abuse, they can lead to various forms of emotional illness. They can also lead to incredible resilience and almost superhuman behaviors, seemingly, if people can come through those experiences intact. I don't know if we—we being
2952-403: Is distinct from somatic action potentials in three ways: 1. The signal has a shorter peak-trough duration (~150μs) than of pyramidal cells (~500μs) or interneurons (~250μs). 2. The voltage change is triphasic. 3. Activity recorded on a tetrode is seen on only one of the four recording wires. In recordings from freely moving rats, axonal signals have been isolated in white matter tracts including
3075-406: Is due to factors other than mental illness. In a 2015 New Republic essay, Columbine author Dave Cullen describes a subset of school shooters (and other mass murderers) known as "injustice collectors", or people who "never forget, never forgive, [and] never let go" before they strike out. The essay describes and expands on the work of retired FBI profiler Mary Ellen O'Toole, who has published
3198-604: Is impaired, this is known as Wallerian-like degeneration. Studies suggest that the degeneration happens as a result of the axonal protein NMNAT2 , being prevented from reaching all of the axon. Demyelination of axons causes the multitude of neurological symptoms found in the disease multiple sclerosis . Dysmyelination is the abnormal formation of the myelin sheath. This is implicated in several leukodystrophies , and also in schizophrenia . A severe traumatic brain injury can result in widespread lesions to nerve tracts damaging
3321-507: Is involved in the activation of TrkA at the tip of neutrites, is required for the elongation of axons. PMGS asymmetrically distributes to the tip of the neurite that is destined to become the future axon. During axonal development, the activity of PI3K is increased at the tip of destined axon. Disrupting the activity of PI3K inhibits axonal development. Activation of PI3K results in the production of phosphatidylinositol (3,4,5)-trisphosphate (PtdIns) which can cause significant elongation of
3444-528: Is little to no data supporting this hypothesis (Ferguson, 2009) but it has become a vivid profile used by the media since the Columbine Massacre in 1999. A summation of past research on video game violence finds that video games have little to no effect on aggression. (Anderson, 2004; Ferguson, 2007 & Spencer, 2009) Again, this supports the idea that although it is a popular opinion to link school shooters to being violent video gamers; this misconception
3567-606: Is needed with greater scope on investigations, to understand whether this is a real phenomenon or not. Some attribute this to copycat behavior, which can be correlated with the level of media exposure. In these copycat shootings, oftentimes the perpetrators see a past school shooter as an idol, so they want to carry out an even more destructive, murderous shooting in hopes of gaining recognition or respect. Some mass murderers study media reports of previous killers. Recent premeditative writings were presented according to court documents and showed Joshua O'Connor wrote that he wanted
3690-416: Is often attributable to third variables and has not been supported by research on the connection between aggression and gaming. One of the infamous books, the 1977 novel Rage by Stephen King (written under the pseudonym Richard Bachman ), was linked to five school shootings and hostage situations that took place between 1988 and 1997; the most recent of these, the 1997 Heath High School shooting ,
3813-400: Is that school shooters tended to isolate themselves, and "exhibited an obsessive quality that often led to detailed planning, but ironically they seemed to lack an understanding of the consequences of their behavior and thus may have a history of adverse encounters with law enforcement." A criticism in the media of past shooters was questioning how so much planning could commence without alerting
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3936-402: Is the corpus callosum that connects the two cerebral hemispheres , and this has around 20 million axons. The structure of a neuron is seen to consist of two separate functional regions, or compartments – the cell body together with the dendrites as one region, and the axonal region as the other. The axonal region or compartment, includes the axon hillock, the initial segment,
4059-411: Is the area formed from the cell body of the neuron as it extends to become the axon. It precedes the initial segment. The received action potentials that are summed in the neuron are transmitted to the axon hillock for the generation of an action potential from the initial segment. The axonal initial segment (AIS) is a structurally and functionally separate microdomain of the axon. One function of
4182-401: Is the culprit for school shootings in lieu of the accessibility of guns or other environmental factors. The authors expressed concern that proposals to target gun control laws at people with mental illness do not take into account the complex nature of the relationship between serious mental illness and violence, much of which is due to additional factors such as substance abuse. However, the link
4305-461: Is the spark that push some to return to school with a gun, buying software not based on school shooting studies to evaluate threats although killers rarely make direct threats, and reliance on metal detectors and police officers in schools when shooters often make no effort to conceal their weapons. In May 2002, the Secret Service published a report that examined 37 U.S. school shootings. They had
4428-426: Is thought to carry a different cargo. The studies on transport in the axon led to the naming of kinesin. In the nervous system, axons may be myelinated , or unmyelinated. This is the provision of an insulating layer, called a myelin sheath. The myelin membrane is unique in its relatively high lipid to protein ratio. In the peripheral nervous system axons are myelinated by glial cells known as Schwann cells . In
4551-633: Is unclear since research has shown that violence in mentally ill people occurs more in interpersonal environments. It is also mentionable that school size can play a role on the presence of shooter mental health concerns. In a presented study from researchers Baird, Roellke & Zeifman from the Social Science Journal, it is presented that school size and level of attention given to students can precede violent actions, as students who commit mass shootings in larger schools are likely to have transitioned from smaller schools. This adds important nuance to
4674-449: Is unmyelinated and contains a specialized complex of proteins. It is between approximately 20 and 60 μm in length and functions as the site of action potential initiation. Both the position on the axon and the length of the AIS can change showing a degree of plasticity that can fine-tune the neuronal output. A longer AIS is associated with a greater excitability. Plasticity is also seen in
4797-605: The District of Columbia have experienced a shooting. Many school shootings in the United States result in one non-fatal injury. The type of firearm most commonly used in school shootings in the United States is the handgun . Three school shootings (the Columbine massacre, the Sandy Hook massacre, and the 2018 Parkland High School shooting in Florida), accounted for 43% of the fatalities;
4920-545: The Substance Abuse and Mental Health Services Administration (SAMHSA) revealed that substance abuse amongst children raised by single mothers was higher than children raised by both of their biological parents. However, the percentage of substance abuse amongst children raised by single mothers was not only remarkably low (5.4%), but also only 1.2% higher than children raised by both their parents. Those rates are revealed to be even smaller when compared to other demographics of
5043-539: The US Secret Service and US Department of Education found evidence that a majority of school shooters displayed evidence of mental health symptoms, often undiagnosed or untreated. Criminologists Fox and DeLateur note that mental illness is only part of the issue, however, and mass shooters tend to externalize their problems, blaming others and are unlikely to seek psychiatric help, even if available. According to an article written on gun violence and mental illness,
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5166-600: The United States Department of Justice , published a review of deaths related to schools occurring as a result of violence, including explicitly "unintentional firearm-related death", for the academic years 1992–1993 and 1993–1994. A second study (Anderson; Kaufman; Simon 2001), a continuation from the 1996 study, was published December 5, and covered the period 1994–1999. A United States Secret Service study concluded that schools were placing false hope in physical security, when they should be paying more attention to
5289-418: The guidance of neuronal axon growth. These cells that help axon guidance , are typically other neurons that are sometimes immature. When the axon has completed its growth at its connection to the target, the diameter of the axon can increase by up to five times, depending on the speed of conduction required. It has also been discovered through research that if the axons of a neuron were damaged, as long as
5412-462: The immunoglobulin superfamily. Another set of molecules called extracellular matrix - adhesion molecules also provide a sticky substrate for axons to grow along. Examples of these molecules include laminin , fibronectin , tenascin , and perlecan . Some of these are surface bound to cells and thus act as short range attractants or repellents. Others are difusible ligands and thus can have long range effects. Cells called guidepost cells assist in
5535-404: The neurotransmitter for release at the synapse . This makes multiple synaptic connections with other neurons possible. Sometimes the axon of a neuron may synapse onto dendrites of the same neuron, when it is known as an autapse . Some synaptic junctions appear along the length of an axon as it extends; these are called en passant boutons ("in passing boutons") and can be in the hundreds or even
5658-451: The "death count to be as high as possible so that the shooting would be infamous". O'Connor was arrested before he was able to carry out his plan. Infamy and notoriety, "a desire to be remembered" has been reported as the leading reason for planned shootings by most perpetrators who were taken alive either pre or post shooting. School shootings are a "modern phenomenon". There were scattered instances of gunmen or bombers attacking schools in
5781-413: The "non-traditional" household perspective, which focuses on how family structure and family stability are related to child outcomes. Broadly speaking, proponents of this hypothesis claim that family structures such as single mothers, same-sex parents, extended family, or cohabitation are more harmful to the development of a child's mental well-being, than heterosexual, married parents (often equated with
5904-468: The 1998 Thurston High School shooting , used to be the deadliest high school shootings in modern U.S. history until they were both surpassed by the April 1999 Columbine High School massacre . This California school-related article is a stub . You can help Misplaced Pages by expanding it . School shooting A school shooting is an armed attack at an educational institution , such as
6027-505: The 2001 Santana High School shooting in California , the 2018 Marshall County High School shooting in Kentucky, and Stoneman Douglas. There were 11 firearm-related events that occurred at a school or campus in the first 23 days of 2018. As of May 2018, more people, including students and teachers, were killed in 2018 in schools in the United States than were killed in military service for
6150-668: The 2001 Santana High School shooting in Santee, California , in which two were killed; the 2018 Marshall County High School shooting in Benton, Kentucky , in which two were killed; and the 2021 Oxford High School shooting in Oxford Township, Michigan , in which four were killed. During 1996, the CDC ( Centers for Disease Control and Prevention ) together with the US Department of Education and
6273-482: The Australian-based Raising children network and Centre for Adolescent Health (and other sources): the main change occurring in the developing brain during adolescence is the (so-called) pruning of unused connections in thinking and processing. While this is occurring within the brain, retained connections are strengthened. Synaptic pruning occurs because the nervous system in humans develops by firstly,
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#17329098982566396-922: The Aα, Aβ, and Aγ nerve fibers, respectively. Later findings by other researchers identified two groups of Aa fibers that were sensory fibers. These were then introduced into a system (Lloyd classification) that only included sensory fibers (though some of these were mixed nerves and were also motor fibers). This system refers to the sensory groups as Types and uses Roman numerals: Type Ia, Type Ib, Type II, Type III, and Type IV. Lower motor neurons have two kind of fibers: Different sensory receptors are innervated by different types of nerve fibers. Proprioceptors are innervated by type Ia, Ib and II sensory fibers, mechanoreceptors by type II and III sensory fibers and nociceptors and thermoreceptors by type III and IV sensory fibers. The autonomic nervous system has two kinds of peripheral fibers: In order of degree of severity, injury to
6519-424: The Columbine attack or cited the Columbine perpetrators Eric Harris and Dylan Klebold as inspiration. At least 68 schools that experienced a school shooting employed a police officer or security guard; in all but a few, the shooting ended before any intercession. Security guards or resource officers were present during four of the five school shooting incidents with the highest number of dead or injured: Columbine,
6642-410: The United States and 14 in the rest of the world combined. Between 2000 and 2010, counting incidents from 37 countries in which someone was injured or killed on school grounds, with two or more victims, and not counting "single homicides, off-campus homicides, killings caused by government actions, militaries, terrorists or militants", the number of such incidents in the United States was one less than in
6765-498: The United States was made more difficult by the passage by United States Congress of the Dickey Amendment in 1996, which mandated that no Centers for Disease Control and Prevention funds "may be used to advocate or promote gun control", although this does not mean the CDC has stopped researching gun violence. Instead, Congress relies on independent research done by non-partisan organizations for getting data on gun violence in
6888-644: The United States, including both combat and non-combat military service, according to an analysis by The Washington Post . In terms of the year-to-date number of individual deadly school shootings incidents in the United States, early 2018 was much higher than 2017, with 16 in 2018 and four in 2017, through May; the year-to-day through May number of incidents was the highest since 1999. As of May 2018, thirteen school shootings took place on K–12 school property in 2018 that resulted in firearm-related injuries or deaths, including 32 killed and 65 injured, according to Education Week . 22 school shootings where someone
7011-539: The United States. Between the Columbine massacre and the Santa Fe High School shooting in Texas , shooting of some form happened at 216 schools, and at least 141 children, educators and other people were killed and another 284 were injured. 38% of the students who experienced school shootings were African American although African American students were 16.6% of the school population. Schools in at least 36 states and
7134-461: The ability of the AIS to change its distribution and to maintain the activity of neural circuitry at a constant level. The AIS is highly specialized for the fast conduction of nerve impulses . This is achieved by a high concentration of voltage-gated sodium channels in the initial segment where the action potential is initiated. The ion channels are accompanied by a high number of cell adhesion molecules and scaffold proteins that anchor them to
7257-399: The alveus and the corpus callosum as well hippocampal gray matter. In fact, the generation of action potentials in vivo is sequential in nature, and these sequential spikes constitute the digital codes in the neurons. Although previous studies indicate an axonal origin of a single spike evoked by short-term pulses, physiological signals in vivo trigger the initiation of sequential spikes at
7380-452: The assumption that a perpetrator can be identified by a certain 'type' or profile. The results from the study indicated that perpetrators came from differing backgrounds, making a singular profile difficult when identifying a possible assailant. For example, some perpetrators were children of divorce, lived in foster homes, or came from intact nuclear families. The majority of individuals had rarely or never gotten into trouble at school and had
7503-538: The availability of firearms in the United States. Children at U.S. schools have active shooter drills. According to USA Today , in 2019 "about 95% of public schools now have students and teachers practice huddling in silence, hiding from an imaginary gunman." Between the 1999 Columbine High School massacre in Colorado and the 2012 Sandy Hook Elementary School shooting in Connecticut , there were 31 school shootings in
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#17329098982567626-406: The axon is to transmit information to different neurons, muscles, and glands. In certain sensory neurons ( pseudounipolar neurons ), such as those for touch and warmth, the axons are called afferent nerve fibers and the electrical impulse travels along these from the periphery to the cell body and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction can be
7749-503: The axon length on the molecular level. These studies suggest that motor proteins carry signaling molecules from the soma to the growth cone and vice versa whose concentration oscillates in time with a length-dependent frequency. The axons of neurons in the human peripheral nervous system can be classified based on their physical features and signal conduction properties. Axons were known to have different thicknesses (from 0.1 to 20 μm) and these differences were thought to relate to
7872-400: The axon sometimes consists of several regions that function more or less independently of each other. Axons are covered by a membrane known as an axolemma ; the cytoplasm of an axon is called axoplasm . Most axons branch, in some cases very profusely. The end branches of an axon are called telodendria . The swollen end of a telodendron is known as the axon terminal or end-foot which joins
7995-415: The axon to its target, is one of the six major stages in the overall development of the nervous system . Studies done on cultured hippocampal neurons suggest that neurons initially produce multiple neurites that are equivalent, yet only one of these neurites is destined to become the axon. It is unclear whether axon specification precedes axon elongation or vice versa, although recent evidence points to
8118-399: The axon's membrane and empty their contents into the extracellular space. The neurotransmitter is released from the presynaptic nerve through exocytosis . The neurotransmitter chemical then diffuses across to receptors located on the membrane of the target cell. The neurotransmitter binds to these receptors and activates them. Depending on the type of receptors that are activated, the effect on
8241-416: The axons in a condition known as diffuse axonal injury . This can lead to a persistent vegetative state . It has been shown in studies on the rat that axonal damage from a single mild traumatic brain injury, can leave a susceptibility to further damage, after repeated mild traumatic brain injuries. A nerve guidance conduit is an artificial means of guiding axon growth to enable neuroregeneration , and
8364-428: The beauty college campus too early. Upon his arrest, he was without remorse, saying simply, "I wanted people to know who I was." Towers, et al. (2015), found a small, but significant temporary increase in the probability of a second school shooting within 2 weeks after a known school shooting, which was only slightly smaller than the probability of repeats after mass killings involving firearms. However, much more work
8487-551: The brain and generate thousands of synaptic terminals. A bundle of axons make a nerve tract in the central nervous system , and a fascicle in the peripheral nervous system . In placental mammals the largest white matter tract in the brain is the corpus callosum , formed of some 200 million axons in the human brain . Axons are the primary transmission lines of the nervous system , and as bundles they form nerves . Some axons can extend up to one meter or more while others extend as little as one millimeter. The longest axons in
8610-455: The brain. The myelin gives the white appearance to the tissue in contrast to the grey matter of the cerebral cortex which contains the neuronal cell bodies. A similar arrangement is seen in the cerebellum . Bundles of myelinated axons make up the nerve tracts in the CNS. Where these tracts cross the midline of the brain to connect opposite regions they are called commissures . The largest of these
8733-416: The cause of many inherited and acquired neurological disorders that affect both the peripheral and central neurons . Nerve fibers are classed into three types – group A nerve fibers , group B nerve fibers , and group C nerve fibers . Groups A and B are myelinated , and group C are unmyelinated. These groups include both sensory fibers and motor fibers. Another classification groups only
8856-443: The cell bodies of the neurons. In addition to propagating action potentials to axonal terminals, the axon is able to amplify the action potentials, which makes sure a secure propagation of sequential action potentials toward the axonal terminal. In terms of molecular mechanisms, voltage-gated sodium channels in the axons possess lower threshold and shorter refractory period in response to short-term pulses. The development of
8979-483: The cell body along the axon, carries mitochondria and membrane proteins needed for growth to the axon terminal. Ingoing retrograde transport carries cell waste materials from the axon terminal to the cell body. Outgoing and ingoing tracks use different sets of motor proteins . Outgoing transport is provided by kinesin , and ingoing return traffic is provided by dynein . Dynein is minus-end directed. There are many forms of kinesin and dynein motor proteins, and each
9102-594: The cell body and terminating at points where the axon makes synaptic contact with target cells. The defining characteristic of an action potential is that it is "all-or-nothing" – every action potential that an axon generates has essentially the same size and shape. This all-or-nothing characteristic allows action potentials to be transmitted from one end of a long axon to the other without any reduction in size. There are, however, some types of neurons with short axons that carry graded electrochemical signals, of variable amplitude. When an action potential reaches
9225-504: The central nervous system the myelin sheath is provided by another type of glial cell, the oligodendrocyte . Schwann cells myelinate a single axon. An oligodendrocyte can myelinate up to 50 axons. The composition of myelin is different in the two types. In the CNS the major myelin protein is proteolipid protein , and in the PNS it is myelin basic protein . Nodes of Ranvier (also known as myelin sheath gaps ) are short unmyelinated segments of
9348-559: The context of a feud, were about three times as common as those that appeared indiscriminate. Most perpetrators of school shootings exhibited no signs of debilitating mental disorder , such as psychosis or schizophrenia , although most mass killers typically have or exhibit signs of depression. On the other hand, Eric Harris was almost certainly a psychopath as noted by the FBI. Between the Columbine massacre and 2015, "more than 40 people" were "charged with Columbine-style plots;" almost all were white male teenagers and almost all had studied
9471-487: The control group thought that gun restrictions should be applied to people with mental illness, and nearly 80% of participants who read the articles agreed. Despite the fact that the article exposed the readers to both the mental illness of the shooter, and the fact that the shooter used high-capacity magazines, participants advocated more for gun restrictions on people with mental illness rather than bans on high-capacity magazines. This suggests that people believe mental illness
9594-403: The crime for an episode or use it as a plot point for about half a season. Axons An axon (from Greek ἄξων áxōn , axis) or nerve fiber (or nerve fibre : see spelling differences ) is a long, slender projection of a nerve cell, or neuron , in vertebrates , that typically conducts electrical impulses known as action potentials away from the nerve cell body . The function of
9717-418: The cytoskeleton. Interactions with ankyrin-G are important as it is the major organizer in the AIS. The axoplasm is the equivalent of cytoplasm in the cell. Microtubules form in the axoplasm at the axon hillock. They are arranged along the length of the axon, in overlapping sections, and all point in the same direction – towards the axon terminals. This is noted by the positive endings of
9840-412: The dendrite or cell body of another neuron forming a synaptic connection. Axons usually make contact with other neurons at junctions called synapses but can also make contact with muscle or gland cells. In some circumstances, the axon of one neuron may form a synapse with the dendrites of the same neuron, resulting in an autapse . At a synapse, the membrane of the axon closely adjoins the membrane of
9963-481: The entire process adheres to surfaces and explores the surrounding environment. Actin plays a major role in the mobility of this system. Environments with high levels of cell adhesion molecules (CAMs) create an ideal environment for axonal growth. This seems to provide a "sticky" surface for axons to grow along. Examples of CAMs specific to neural systems include N-CAM , TAG-1 – an axonal glycoprotein – and MAG , all of which are part of
10086-486: The existence of violence as an outlet for the mentally ill is quite prominent in some instances (Swanson et al., 2015). The article lists from a study that 12% of people with serious mental illness had committed minor or serious violence within the last year, compared to 2% of people without illness committing those same acts. Other scholars have concluded that mass murderers display a common constellation of chronic mental health symptoms, chronic anger or antisocial traits, and
10209-476: The expense of other factors such as the availability of high-capacity magazines. Nearly 2,000 participants read a news piece on a shooting in which the shooter is diagnosed as having a mental illness and who used high capacity magazines. One group read an article that presented only the facts of the case. A different group read an article about the same shooting, but in it the author advocated for gun restrictions for people with mental illness. Another group read about
10332-483: The fibers into three main groups using the letters A, B, and C. These groups, group A , group B , and group C include both the sensory fibers ( afferents ) and the motor fibers ( efferents ). The first group A, was subdivided into alpha, beta, gamma, and delta fibers – Aα, Aβ, Aγ, and Aδ. The motor neurons of the different motor fibers, were the lower motor neurons – alpha motor neuron , beta motor neuron , and gamma motor neuron having
10455-470: The field in general—have discovered what the keys are, what makes the difference for kids." Understanding that socio-economic factors have greater effects on child development and emotional stability have led many to argue that single-parent and other non-traditional households should be afforded equivalent incentives by the state, as are afforded married households, and that focusing on family structure rather than family stability derails efforts to understand
10578-527: The following findings: There have been many representations of American school shootings in films and TV shows produced by both United States and international production companies. While films Elephant , We Need to Talk about Kevin , Beautiful Boy , and Mass are solely focused on the either the act or the aftermath, many of the shows such as Criminal Minds , Degrassi: the Next Generation , Law and Order , and One Tree Hill investigate
10701-411: The formation of multiple axons. Consequently, the interruption of the actin network in a growth cone will promote its neurite to become the axon. Growing axons move through their environment via the growth cone , which is at the tip of the axon. The growth cone has a broad sheet-like extension called a lamellipodium which contain protrusions called filopodia . The filopodia are the mechanism by which
10824-507: The guns used were taken from their homes or relative's home. The availability of firearms has direct effect on the probability of initiating a school shooting. This has led many to question whether parents should be held criminally negligent for their children's gun-related crimes. By 2018, a total of four parents were convicted of failing to lock up the guns that were used to shoot up US schools by their children. Such incidents may also lead to nationwide discussion on gun laws. The FBI offer
10947-433: The hallmark of traumatic brain injuries . Axonal damage is usually to the axon cytoskeleton disrupting transport. As a consequence protein accumulations such as amyloid-beta precursor protein can build up in a swelling resulting in a number of varicosities along the axon. Most axons carry signals in the form of action potentials, which are discrete electrochemical impulses that travel rapidly along an axon, starting at
11070-408: The human body are those of the sciatic nerve , which run from the base of the spinal cord to the big toe of each foot. The diameter of axons is also variable. Most individual axons are microscopic in diameter (typically about one micrometer (μm) across). The largest mammalian axons can reach a diameter of up to 20 μm. The squid giant axon , which is specialized to conduct signals very rapidly,
11193-506: The idea of a nuclear family ). This perspective is found to back federal efforts such as the Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA) of 1996 and US federal tax incentives. However, these assumptions on the detrimental effects of "non-traditional" family structures have repeatedly been shown to be false, with the true issues lying within socio-economic realities. Longitudinal research has shown
11316-507: The idea that larger schools are more prone to mass violence by showing that the stress associated with losing the personal support given in a smaller community is a weight on students. A 2016 opinion piece published by U.S. News & World Report concluded that 22% of mass murders are committed by people who suffer from a serious mental illness, and 78% do not. This study also concluded that many people with mental illnesses do not engage in violence against others and that most violent behavior
11439-403: The initial segment is to separate the main part of an axon from the rest of the neuron; another function is to help initiate action potentials. Both of these functions support neuron cell polarity , in which dendrites (and, in some cases the soma ) of a neuron receive input signals at the basal region, and at the apical region the neuron's axon provides output signals. The axon initial segment
11562-451: The integration of synaptic messages at the scale of the neuron. Extracellular recordings of action potential propagation in axons has been demonstrated in freely moving animals. While extracellular somatic action potentials have been used to study cellular activity in freely moving animals such as place cells , axonal activity in both white and gray matter can also be recorded. Extracellular recordings of axon action potential propagation
11685-502: The issue that school shooters do not necessarily come from "bad" parents. No more than they could come from attentive, educated, negligent, single, married, abusive, or loving parents. Dorothy Espelage of the University of Florida observed that 8% of bullying victims become "angry, and aggressively so." She added, "They become very angry, they may act out aggressively online. They may not hit back, but they definitely ruminate." "Bullying
11808-433: The latter. If an axon that is not fully developed is cut, the polarity can change and other neurites can potentially become the axon. This alteration of polarity only occurs when the axon is cut at least 10 μm shorter than the other neurites. After the incision is made, the longest neurite will become the future axon and all the other neurites, including the original axon, will turn into dendrites. Imposing an external force on
11931-419: The microtubules. This overlapping arrangement provides the routes for the transport of different materials from the cell body. Studies on the axoplasm has shown the movement of numerous vesicles of all sizes to be seen along cytoskeletal filaments – the microtubules, and neurofilaments , in both directions between the axon and its terminals and the cell body. Outgoing anterograde transport from
12054-439: The myelin sheath of a myelinated axon. Oligodendrocytes form the insulating myelin in the CNS. Along myelinated nerve fibers, gaps in the myelin sheath known as nodes of Ranvier occur at evenly spaced intervals. The myelination enables an especially rapid mode of electrical impulse propagation called saltatory conduction . The myelinated axons from the cortical neurons form the bulk of the neural tissue called white matter in
12177-499: The neuron. Axons vary largely in length from a few micrometers up to meters in some animals. This emphasizes that there must be a cellular length regulation mechanism allowing the neurons both to sense the length of their axons and to control their growth accordingly. It was discovered that motor proteins play an important role in regulating the length of axons. Based on this observation, researchers developed an explicit model for axonal growth describing how motor proteins could affect
12300-471: The number of children were killed in schools in the early 1990s than today". On August 27, 2018, NPR reported that a U.S. Education Department report, released earlier in the year, for the 2015–2016 school year said "nearly 240 schools ... reported at least 1 incident involving a school-related shooting". However, when NPR researched this 'claim', it could confirm only 11 actual incidents. School shootings are an "overwhelmingly American" phenomenon due to
12423-426: The other 36 countries combined; in the vast majority of the United States incidents, perpetrators used guns. A U.S. Education Department report, released earlier in the year, for the 2015–2016 school year said "nearly 240 schools ... reported at least 1 incident involving a school-related shooting". NPR independently evaluated this claim and only confirmed 11 of the 240 cited incidents. Addressing school shootings in
12546-431: The over-producing of parts of the nervous system, axons , neurons , and synapses , to then later in the development of the nervous system, make the superfluous parts redundant, i.e. pruning (or apoptosis , otherwise known as cell death ). These changes occur in certain parts of the brain firstly; the pre-frontal cortex , the brain location where decision-making occurs, is the concluding area for development. While
12669-601: The parents or guardians to their efforts. However, this has proven to be as difficult of a question to answer as anticipating any of the past school shootings. Data from the National Center for the Analysis of Violent Crime and Centers for Disease Control and Prevention , covering decades of US school shootings, reveals that 68% of shooters obtained weapons from their home or the home of a relative. Since 1999, out of 145 US school shootings committed by children/adolescents, 80% of
12792-417: The pre-attack behaviors of students. Zero-tolerance policies and metal detectors "are unlikely to be helpful," the Secret Service researchers found. The researchers focused on questions concerning the reliance on SWAT teams when most attacks are over before police arrive, profiling of students who show warning signs in the absence of a definitive profile, expulsion of students for minor infractions when expulsion
12915-410: The pre-frontal cortex is developing, children and teenagers might possibly rely more on the brain part known as the amygdala ; involving thinking that is more emotionally active, including aggression and impulsiveness . As a consequence each individual is more likely to want to make riskier choices, and to do so more frequently. One assumption into the catalytic causes of school shootings comes from
13038-436: The realities of mass-shooters. "Studies have found that within offenders' families, there is frequently a lack of supervision, low emotional closeness, and intimacy". In a 2018 publication, Dr. George S. Everly Jr, of The Johns Hopkins School of Medicine and The Johns Hopkins Bloomberg School of Public Health outlined an accumulation of seven, recurring themes that warrant consideration regarding school shooters. One factor
13161-477: The rest of the axon, and the axon telodendria, and axon terminals. It also includes the myelin sheath. The Nissl bodies that produce the neuronal proteins are absent in the axonal region. Proteins needed for the growth of the axon, and the removal of waste materials, need a framework for transport. This axonal transport is provided for in the axoplasm by arrangements of microtubules and type IV intermediate filaments known as neurofilaments . The axon hillock
13284-417: The robust, positive effects of higher incomes and higher education levels on child well-being and emotional development, which reflects on the family stability , and not family structure. Further, proponents of this hypothesis often cite family statistics for those who commit crimes, but leave out how these compare to other populations, including the general population. For example, a 2009 survey conducted by
13407-492: The same time period. According to surveys commissioned by the National Institute on Drug Abuse , between 20 and 30% of teenagers used/abused illicit substances, a much higher rate than single mother households. Another example of poorly-cited statistics to further this narrative can be found in children who have lost at least one parent. In the U.S., the rate of parental death before age 16 is 8%. The rate of parental death
13530-761: The sensory fibers as Type I, Type II, Type III, and Type IV. An axon is one of two types of cytoplasmic protrusions from the cell body of a neuron; the other type is a dendrite . Axons are distinguished from dendrites by several features, including shape (dendrites often taper while axons usually maintain a constant radius), length (dendrites are restricted to a small region around the cell body while axons can be much longer), and function (dendrites receive signals whereas axons transmit them). Some types of neurons have no axon and transmit signals from their dendrites. In some species, axons can emanate from dendrites known as axon-carrying dendrites. No neuron ever has more than one axon; however in invertebrates such as insects or leeches
13653-426: The shooting in an article that suggested the proposal to ban large-capacity magazines, which acted to advocate that shootings could stem from a societal problem rather than an individual problem. The control group did not read anything. Participants were then all asked to fill in a questionnaire asking about their views on gun control and whether they thought there should be restrictions on high-capacity magazines. 71% of
13776-404: The simultaneous transmission of messages to a large number of target neurons within a single region of the brain. There are two types of axons in the nervous system: myelinated and unmyelinated axons. Myelin is a layer of a fatty insulating substance, which is formed by two types of glial cells : Schwann cells and oligodendrocytes . In the peripheral nervous system Schwann cells form
13899-489: The soma (the cell body of a neuron) is not damaged, the axons would regenerate and remake the synaptic connections with neurons with the help of guidepost cells . This is also referred to as neuroregeneration . Nogo-A is a type of neurite outgrowth inhibitory component that is present in the central nervous system myelin membranes (found in an axon). It has a crucial role in restricting axonal regeneration in adult mammalian central nervous system. In recent studies, if Nogo-A
14022-475: The speed at which an action potential could travel along the axon – its conductance velocity . Erlanger and Gasser proved this hypothesis, and identified several types of nerve fiber, establishing a relationship between the diameter of an axon and its nerve conduction velocity. They published their findings in 1941 giving the first classification of axons. Axons are classified in two systems. The first one introduced by Erlanger and Gasser, grouped
14145-411: The target cell can be to excite the target cell, inhibit it, or alter its metabolism in some way. This entire sequence of events often takes place in less than a thousandth of a second. Afterward, inside the presynaptic terminal, a new set of vesicles is moved into position next to the membrane, ready to be released when the next action potential arrives. The action potential is the final electrical step in
14268-473: The target cell, and special molecular structures serve to transmit electrical or electrochemical signals across the gap. Some synaptic junctions appear along the length of an axon as it extends; these are called en passant boutons ("in passing boutons") and can be in the hundreds or even the thousands along one axon. Other synapses appear as terminals at the ends of axonal branches. A single axon, with all its branches taken together, can target multiple parts of
14391-444: The thousands along one axon. In the normally developed brain, along the shaft of some axons are located pre-synaptic boutons also known as axonal varicosities and these have been found in regions of the hippocampus that function in the release of neurotransmitters. However, axonal varicosities are also present in neurodegenerative diseases where they interfere with the conduction of an action potential. Axonal varicosities are also
14514-525: The type of firearm used in the most lethal school shootings was the rifle . High-capacity magazines , which allow the perpetrator to fire dozens of rounds without having to reload, were used in the Columbine and Sandy Hook shootings. 70% of the perpetrators of school shootings were under the age of 18, with the median age of 16. More than 85% of the perpetrators of school shootings obtained their firearms from their own homes or from friends or relatives. Targeted school shootings, those occurring for example in
14637-402: The view that school shooters are often people who play violent video games is more simply explained by the third variable of gender. The idea of profiling school shooters by the video games they play comes from the belief that playing violent video games increases a person's aggression level, which in turn, can cause people to perpetrate extreme acts of violence, such as a school shooting. There
14760-594: The years before the Frontier Middle School shooting in Moses Lake, Washington in 1996, "but they were lower profile", according to journalist Malcolm Gladwell in 2015. In the United States specifically, the most recent trend has been downward following the spikes of the 1990s, yet at the same time they are trending towards a higher likelihood of being premeditated and executed with a strict plan in mind. A study by Northeastern University found that "four times
14883-469: Was hurt or killed occurred in the United States in the first 20 weeks of 2018, according to CNN . As of May 22, 2023, the ten deadliest school shootings in the United States since the 1999 Columbine High School massacre in Colorado in which 13 were killed were the: Other school shootings occurring in the United States include the 1966 University of Texas tower shooting in Austin in which 16 were killed;
15006-567: Was seeking fame, but with the new television news climate, they received it anyway. Seeing this, 18-year-old Robert Benjamin Smith bought a gun, and on November 12, 1966, he killed four women and a toddler inside the Rose-Mar College of Beauty in Mesa, Arizona. "I wanted to get known, just wanted to get myself a name," explained Smith. He had hoped to kill nearly ten times as many people but had arrived at
15129-611: Was ultimately influential in King's decision to pull the book out of print for good. Shooting massacres in English-speaking countries often occur close together in time. In the summer of 1966, two major stories broke: Richard Speck murdered eight women on a single night in Chicago, and Charles Whitman shot and killed 15 people from a clock tower at the University of Texas in Austin. Neither
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