What You Need to Know About Neurons
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Introduction
The Compages of the Neuron
Nascence
Migration
Differentiation
Death
Hope Through Inquiry
Introduction
Until recently, most neuroscientists idea we were born with all the neurons we were ever going to have. As children nosotros might produce some new neurons to assist build the pathways - chosen neural circuits - that human activity as information highways between dissimilar areas of the brain. But scientists believed that in one case a neural circuit was in identify, calculation any new neurons would disrupt the flow of information and disable the brain's communication organisation.
In 1962, scientist Joseph Altman challenged this belief when he saw testify of neurogenesis (the nascence of neurons) in a region of the adult rat encephalon called the hippocampus. He later reported that newborn neurons migrated from their birthplace in the hippocampus to other parts of the brain. In 1979, another scientist, Michael Kaplan, confirmed Altman's findings in the rat brain, and in 1983 he found neural precursor cells in the forebrain of an developed monkey.
These discoveries about neurogenesis in the adult brain were surprising to other researchers who didn't think they could be true in humans. Only in the early 1980s, a scientist trying to empathise how birds learn to sing suggested that neuroscientists look again at neurogenesis in the developed brain and begin to run across how information technology might make sense. In a series of experiments, Fernando Nottebohm and his research team showed that the numbers of neurons in the forebrains of male person canaries dramatically increased during the mating flavor. This was the same time in which the birds had to learn new songs to attract females.
Why did these bird brains add neurons at such a critical time in learning? Nottebohm believed information technology was because fresh neurons helped store new song patterns inside the neural circuits of the forebrain, the expanse of the encephalon that controls complex behaviors. These new neurons made learning possible. If birds made new neurons to assist them remember and learn, Nottebohm idea the brains of mammals might too.
Other scientists believed these findings could not employ to mammals, but Elizabeth Gould later establish evidence of newborn neurons in a distinct area of the brain in monkeys, and Fred Gage and Peter Eriksson showed that the developed human brain produced new neurons in a similar area.
For some neuroscientists, neurogenesis in the developed encephalon is still an unproven theory. But others think the evidence offers intriguing possibilities about the office of adult-generated neurons in learning and memory.
The Architecture of the Neuron
The key nervous system (which includes the encephalon and spinal cord) is made up of two basic types of cells: neurons (1) and glia (4) & (6). Glia outnumber neurons in some parts of the brain, just neurons are the key players in the brain.
Neurons are information messengers. They utilize electrical impulses and chemic signals to transmit information between unlike areas of the brain, and between the brain and the rest of the nervous system. Everything nosotros remember and feel and do would be impossible without the piece of work of neurons and their support cells, the glial cells called astrocytes (4) and oligodendrocytes (6).
Neurons have three bones parts: a cell body and ii extensions chosen an axon (5) and a dendrite (3). Within the cell body is a nucleus (2), which controls the cell's activities and contains the cell'south genetic material. The axon looks like a long tail and transmits letters from the cell. Dendrites look like the branches of a tree and receive messages for the cell. Neurons communicate with each other by sending chemicals, called neurotransmitters, across a tiny infinite, chosen a synapse, between the axons and dendrites of next neurons.
There are three classes of neurons:
- Sensory neurons deport data from the sense organs (such as the eyes and ears) to the encephalon.
- Motor neurons control voluntary muscle activity such as speaking and carry letters from nerve cells in the encephalon to the muscles.
- All the other neurons are choseninterneurons.
Scientists think that neurons are the almost diverse kind of jail cell in the trunk. Within these three classes of neurons are hundreds of different types, each with specific message-carrying abilities.
How these neurons communicate with each other by making connections is what makes each of us unique in how we think, and feel, and act.
Nativity
The extent to which new neurons are generated in the brain is a controversial subject among neuroscientists. Although the majority of neurons are already present in our brains by the time we are born, there is evidence to back up that neurogenesis (the scientific discussion for the birth of neurons) is a lifelong process.
Neurons are born in areas of the brain that are rich in concentrations of neural precursor cells (also called neural stem cells). These cells have the potential to generate nearly, if non all, of the different types of neurons and glia plant in the brain.
Neuroscientists take observed how neural precursor cells behave in the laboratory. Although this may non be exactly how these cells comport when they are in the encephalon, information technology gives united states of america information about how they could be behaving when they are in the brain's environs.
The science of stem cells is still very new, and could modify with additional discoveries, merely researchers have learned enough to exist able to describe how neural stem cells generate the other cells of the brain. They call it a stalk jail cell's lineage and information technology is like in principle to a family tree.
Neural stalk cells increase by dividing in two and producing either 2 new stalk cells, or 2 early progenitor cells, or i of each.
When a stem cell divides to produce another stem jail cell, it is said to self-renew. This new prison cell has the potential to make more than stem cells.
When a stem prison cell divides to produce an early progenitor cell, it is said to differentiate. Differentiation ways that the new prison cell is more specialized in course and part. An early progenitor cell does non have the potential of a stem cell to brand many dissimilar types of cells. It can just make cells in its particular lineage.
Early progenitor cells can self-renew or go in either of two ways. One type will requite rise to astrocytes. The other type will ultimately produce neurons or oligodendrocytes.
Migration
Once a neuron is built-in it has to travel to the identify in the encephalon where it will do its work.
How does a neuron know where to get? What helps information technology get at that place?
Scientists take seen that neurons use at least ii different methods to travel:
- Some neurons drift by post-obit the long fibers of cells called radial glia. These fibers extend from the inner layers to the outer layers of the brain. Neurons glide along the fibers until they reach their destination.
- Neurons besides travel by using chemical signals. Scientists have establish special molecules on the surface of neurons -- adhesion molecules -- that bind with similar molecules on nearby glial cells or nerve axons. These chemical signals guide the neuron to its final location.
Not all neurons are successful in their journey. Scientists recollect that only a third reach their destination. Some cells dice during the procedure of neuronal development.
Some neurons survive the trip, but end up where they shouldn't be. Mutations in the genes that control migration create areas of misplaced or oddly formed neurons that tin cause disorders such equally childhood epilepsy. Some researchers suspect that schizophrenia and the learning disorder dyslexia are partly the result of misguided neurons.
Differentiation
Once a neuron reaches its destination, information technology has to settle in to work. This last step of differentiation is the least well-understood function of neurogenesis.
Neurons are responsible for the transport and uptake of neurotransmitters - chemicals that relay data betwixt brain cells.
Depending on its location, a neuron tin perform the job of a sensory neuron, a motor neuron, or an interneuron, sending and receiving specific neurotransmitters.
In the developing brain, a neuron depends on molecular signals from other cells, such equally astrocytes, to determine its shape and location, the kind of transmitter it produces, and to which other neurons information technology will connect. These freshly born cells found neural circuits - or information pathways connecting neuron to neuron - that will be in place throughout adulthood.
But in the developed brain, neural circuits are already developed and neurons must find a way to fit in. As a new neuron settles in, it starts to wait like surrounding cells. Information technology develops an axon and dendrites and begins to communicate with its neighbors.
Death
Although neurons are the longest living cells in the body, large numbers of them die during migration and differentiation.
The lives of some neurons can take abnormal turns. Some diseases of the encephalon are the issue of the unnatural deaths of neurons.
- InParkinson's disease, neurons that produce the neurotransmitter dopamine die off in the basal ganglia, an area of the brain that controls body movements. This causes difficulty initiating motility.
- InHuntington's affliction, a genetic mutation causes over-production of a neurotransmitter chosen glutamate, which kills neurons in the basal ganglia. As a result, people twist and writhe uncontrollably.
- InAlzheimer's disease, unusual proteins build up in and effectually neurons in the neocortex and hippocampus, parts of the encephalon that control memory. When these neurons die, people lose their capacity to remember and their ability to do everyday tasks. Physical damage to the brain and other parts of the fundamental nervous system tin can also kill or disable neurons.
-Blows to the encephalon, or the damage caused past a stroke, tin can impale neurons outright or slowly starve them of the oxygen and nutrients they need to survive.
-Spinal cord injury can disrupt communication between the brain and muscles when neurons lose their connexion to axons located beneath the site of injury. These neurons may still live, but they lose their ability to communicate.
Hope Through Research
Scientists hope that by understanding more about the life and death of neurons they can develop new treatments, and possibly even cures, for brain diseases and disorders that affect the lives of millions of Americans.
The about electric current inquiry suggests that neural stem cells tin can generate many, if non all, of the unlike types of neurons found in the brain and the nervous system. Learning how to manipulate these stalk cells in the laboratory into specific types of neurons could produce a fresh supply of brain cells to replace those that have died or been damaged.
Therapies could as well be created to take advantage of growth factors and other signaling mechanisms inside the brain that tell forerunner cells to make new neurons. This would make it possible to repair, reshape, and renew the brain from inside.
For information on other neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute's Encephalon Resources and Information Network (Encephalon) at:
Brain
P.O. Box 5801
Bethesda, Doctor 20824
(800) 352-9424
www.ninds.nih.gov
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National Plant of Neurological Disorders and Stroke
National Institutes of Health
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Source: https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Life-and-Death-Neuron
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