Neuron: Difference between revisions

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A '''neurone''', also known as a neuron or nerve cell, is an electrically excitable cell that processes and transmits information through electrical and chemical signals. A chemical signal occurs via a [[#Synapse|synapse]], a specialized connection with other cells. Neurones connect to each other to form neural networks. Neurones are the core components of the nervous system, which includes the brain, spinal cord, and peripheral ganglia. A number of specialized types of neurones exist. Sensory neurones respond to touch, sound, light and numerous other stimuli affecting cells of the sensory organs that then send signals to the spinal cord and brain. Motor neurones receive signals from the brain and spinal cord, cause muscle contractions, and affect glands. Interneurones connect neurones to other neurones within the same region of the brain or spinal cord.

A '''neurone''', also known as a '''neuron''' or '''nerve cell''', is an electrically excitable cell that processes and transmits information through electrical and chemical signals. A chemical signal occurs via a [[#Synapse|synapse]], a specialized connection with other cells. Neurones connect to each other to form neural networks. Neurones are the core components of the nervous system, which includes the brain, spinal cord, and peripheral ganglia.

A number of specialized types of neurones exist. Sensory neurones respond to touch, sound, light and numerous other stimuli affecting cells of the sensory organs that then send signals to the spinal cord and brain. Motor neurones receive signals from the brain and spinal cord, cause muscle contractions, and affect glands. Interneurones connect neurones to other neurones within the same region of the brain or spinal cord.

==Structure==

[[File:MRuueFj.png|320px|thumb|right|Structure of the neurone (click to expand)]]

A typical neurone possesses a cell body (often called the soma), dendrites, and an axon. Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometres ~~and~~ branching multiple times and giving rise to a complex "dendritic tree." An axon is a special cellular extension that arises from the cell body at a site called the axon hillock and travels for a distance. At the majority of synapses, signals are sent from the axon of one neurone to a dendrite of another. There are, however, many exceptions to these rules. For example, there are neurones that lack dendrites, neurones that have no axon, and synapses that connect an axon to another axon or a dendrite to another dendrite, etc.

A typical neurone possesses a cell body (often called the soma), dendrites, and an axon. Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometres, branching multiple times and giving rise to a complex "dendritic tree." An axon is a special cellular extension that arises from the cell body at a site called the axon hillock and travels for a distance. At the majority of synapses, signals are sent from the axon of one neurone to a dendrite of another. There are, however, many exceptions to these rules. For example, there are neurones that lack dendrites, neurones that have no axon, and synapses that connect an axon to another axon or a dendrite to another dendrite, etc.

[[File:Axon.png|330px|thumb|right|Structure of axon membrane]]

[[File:Axon.png|330px|thumb|right|Structure of an axon membrane]]

==Propagation of action potentials==

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==Action upon other neurones==

A neurone affects other neurones by releasing a [[neurotransmitter]] that binds to chemical [[receptor|receptors]]. The effect upon the postsynaptic neurone is determined not by the presynaptic neurone or by the neurotransmitter but by the type of receptor that is activated. Receptors can be classified broadly as [[Neurotransmitter#Excitatory and Inhibitory Effects|excitatory]] (causing an increase in firing rate), [[Neurotransmitter#Excitatory and Inhibitory Effects|inhibitory]] (causing a decrease in firing rate), or modulatory (causing long-lasting effects not directly related to firing rate). The distinction between excitatory and inhibitory neurotransmitters is not absolute~~, however~~. Rather, it depends on the class of chemical receptors present on the postsynaptic neurone. In principle, a single neurone releasing a single neurotransmitter can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still.

A neurone affects other neurones by releasing a [[neurotransmitter]] that binds to chemical [[receptor|receptors]]. The effect upon the postsynaptic neurone is determined not by the presynaptic neurone or by the neurotransmitter but by the type of receptor that is activated. Receptors can be classified broadly as [[Neurotransmitter#Excitatory and Inhibitory Effects|excitatory]] (causing an increase in firing rate), [[Neurotransmitter#Excitatory and Inhibitory Effects|inhibitory]] (causing a decrease in firing rate), or modulatory (causing long-lasting effects not directly related to firing rate). The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neurone. In principle, a single neurone releasing a single neurotransmitter can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still.

==See also==

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-A '''neurone''', also known as a neuron or nerve cell, is an electrically excitable cell that processes and transmits information through electrical and chemical signals. A chemical signal occurs via a [[#Synapse|synapse]], a specialized connection with other cells. Neurones connect to each other to form neural networks. Neurones are the core components of the nervous system, which includes the brain, spinal cord, and peripheral ganglia. A number of specialized types of neurones exist. Sensory neurones respond to touch, sound, light and numerous other stimuli affecting cells of the sensory organs that then send signals to the spinal cord and brain. Motor neurones receive signals from the brain and spinal cord, cause muscle contractions, and affect glands. Interneurones connect neurones to other neurones within the same region of the brain or spinal cord.
+A '''neurone''', also known as a '''neuron''' or '''nerve cell''', is an electrically excitable cell that processes and transmits information through electrical and chemical signals. A chemical signal occurs via a [[#Synapse|synapse]], a specialized connection with other cells. Neurones connect to each other to form neural networks. Neurones are the core components of the nervous system, which includes the brain, spinal cord, and peripheral ganglia.
+A number of specialized types of neurones exist. Sensory neurones respond to touch, sound, light and numerous other stimuli affecting cells of the sensory organs that then send signals to the spinal cord and brain. Motor neurones receive signals from the brain and spinal cord, cause muscle contractions, and affect glands. Interneurones connect neurones to other neurones within the same region of the brain or spinal cord.
 ==Structure==
 [[File:MRuueFj.png|320px|thumb|right|Structure of the neurone (click to expand)]]
-A typical neurone possesses a cell body (often called the soma), dendrites, and an axon. Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometres and branching multiple times and giving rise to a complex "dendritic tree." An axon is a special cellular extension that arises from the cell body at a site called the axon hillock and travels for a distance. At the majority of synapses, signals are sent from the axon of one neurone to a dendrite of another. There are, however, many exceptions to these rules. For example, there are neurones that lack dendrites, neurones that have no axon, and synapses that connect an axon to another axon or a dendrite to another dendrite, etc.
+A typical neurone possesses a cell body (often called the soma), dendrites, and an axon. Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometres, branching multiple times and giving rise to a complex "dendritic tree." An axon is a special cellular extension that arises from the cell body at a site called the axon hillock and travels for a distance. At the majority of synapses, signals are sent from the axon of one neurone to a dendrite of another. There are, however, many exceptions to these rules. For example, there are neurones that lack dendrites, neurones that have no axon, and synapses that connect an axon to another axon or a dendrite to another dendrite, etc.
-[[File:Axon.png|330px|thumb|right|Structure of axon membrane]]
+[[File:Axon.png|330px|thumb|right|Structure of an axon membrane]]
 ==Propagation of action potentials==
@@ Line 20: / Line 22: @@
 ==Action upon other neurones==
-A neurone affects other neurones by releasing a [[neurotransmitter]] that binds to chemical [[receptor|receptors]]. The effect upon the postsynaptic neurone is determined not by the presynaptic neurone or by the neurotransmitter but by the type of receptor that is activated. Receptors can be classified broadly as [[Neurotransmitter#Excitatory and Inhibitory Effects|excitatory]] (causing an increase in firing rate), [[Neurotransmitter#Excitatory and Inhibitory Effects|inhibitory]] (causing a decrease in firing rate), or modulatory (causing long-lasting effects not directly related to firing rate). The distinction between excitatory and inhibitory neurotransmitters is not absolute, however. Rather, it depends on the class of chemical receptors present on the postsynaptic neurone. In principle, a single neurone releasing a single neurotransmitter can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still.
+A neurone affects other neurones by releasing a [[neurotransmitter]] that binds to chemical [[receptor|receptors]]. The effect upon the postsynaptic neurone is determined not by the presynaptic neurone or by the neurotransmitter but by the type of receptor that is activated. Receptors can be classified broadly as [[Neurotransmitter#Excitatory and Inhibitory Effects|excitatory]] (causing an increase in firing rate), [[Neurotransmitter#Excitatory and Inhibitory Effects|inhibitory]] (causing a decrease in firing rate), or modulatory (causing long-lasting effects not directly related to firing rate). The distinction between excitatory and inhibitory neurotransmitters is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neurone. In principle, a single neurone releasing a single neurotransmitter can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still.
 ==See also==