Dendrites

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A Dendrite is an extension of the cell body from a [[Neuron|neuronal]] cell, this the place in a neuronal cell where it receives communication from other neuronal cells and where it is determined whether or not an [[Action_potential|action potential]] is transmitted down the [[axon|axon]]&nbsp;<ref>Alberts et al., 5th edition, G:10</ref>.&nbsp;In a dendrite when neurotransmitters cross the [[synaptic cleft|synaptic cleft]] and bind to receptors on the membrane a signal is transferred, unlike in the axon of a neuronal cell the signal is not an action and in fact a [[Graded potentials|graded potential]]. The graded potential can be of varying strengths and depending on the strength of the graded potential when it reaches the [[axon hillock|axon hillock]] if the graded potentials exceed the threshold level then an action potential is sent down the axon. There are two types of graded potentials, one is [[Excitatory_postsynaptic_potential|excitatory]] and the other is inhibitory. The excitorary potential is known as an EPSP, this is initiated by [[Sodium|Na]]<sup>[[Sodium|+]] </sup>ion&nbsp;channel opening and&nbsp;the entering of Na<sup>+ </sup>ions into the cell depolarising the membrane potential, the inhibitory potential, the IPSP is initiated by the [[Chloride|Cl]]<sup>[[Chloride|-]] </sup>ion channel opening and this [[hyperpolarise|hyperpolarises]] the membrane potential and will as a result cancel out an EPSP and inhibit a action potential being produced.
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A dendrite is an extension of the cell body from a [[Neuron|neuronal]] cell. This the site where communication from other neurones is recieved. &nbsp;It is also at this point where it is determined whether or not an [[Action potential|action potential]] is transmitted down the [[Axon|axon]]&nbsp;<ref>Alberts et al., 5th edition, G:10</ref>.&nbsp;In a dendrite, when neurotransmitters cross the [[Synaptic cleft|synaptic cleft]] and bind to receptors on the membrane, a signal is transferred. Unlike in the axon of a neuronal cell, the signal is not an action potential, but in fact a [[Graded potentials|graded potential]]. Graded potentials can be of varying strengths and depending on the strength of the graded potential when it reaches the [[Axon hillock|axon hillock]].&nbsp;If the graded potentials exceed the threshold level then an action potential is passed down the axon.  
  
=== References ===
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There are two types of graded potentials:&nbsp;[[Excitatory postsynaptic potential|excitatory]] and inhibitory. The excitorary potential is known as an EPSP. This is initiated by [[Sodium|Na]]<sup>[[Sodium|+]] </sup>ion&nbsp;channel opening and&nbsp;the Na<sup>+ </sup>ions entering the membrane, causing depolarisation to occur. The inhibitory potential, the IPSP is initiated by the [[Chloride|Cl]]<sup>[[Chloride|-]] </sup>ion channel opening. This [[Hyperpolarise|hyperpolarises]] the membrane potential and could thus cancel out the EPSP, preventing the action potential from being passed on.
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=== References ===
  
 
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Revision as of 16:46, 30 November 2012

A dendrite is an extension of the cell body from a neuronal cell. This the site where communication from other neurones is recieved.  It is also at this point where it is determined whether or not an action potential is transmitted down the axon [1]. In a dendrite, when neurotransmitters cross the synaptic cleft and bind to receptors on the membrane, a signal is transferred. Unlike in the axon of a neuronal cell, the signal is not an action potential, but in fact a graded potential. Graded potentials can be of varying strengths and depending on the strength of the graded potential when it reaches the axon hillock. If the graded potentials exceed the threshold level then an action potential is passed down the axon.

There are two types of graded potentials: excitatory and inhibitory. The excitorary potential is known as an EPSP. This is initiated by Na+ ion channel opening and the Na+ ions entering the membrane, causing depolarisation to occur. The inhibitory potential, the IPSP is initiated by the Cl- ion channel opening. This hyperpolarises the membrane potential and could thus cancel out the EPSP, preventing the action potential from being passed on.

References

  1. Alberts et al., 5th edition, G:10
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