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| = Neurones are excitable cells that make up the [[Nervous system|nervous system]]. On average a neurone is 20-30µm in diameter, however this varies depending on the type of neurone. A neurone has four main sections; the dendrites, cell body, axon and axon terminals. The axon is where [[Saltatory conduction|saltatory conduction]] causes the [[Propagation|propagation]] of an [[Action potential|action potential]] to move down the axon towards the axon terminal. The axon terminal is where [[Presynaptic modulation|presynaptic modulation]] occurs, and where neurotransmitters are released causing the action potential to be passed to another neurone across the synapse. The dendrites are where [[Graded potentials|graded potentials]] occur. These can either be excitatory postsynaptic potential (EPSP) or inhibitory postsynaptic potential (IPSP). A graded potential is a subthreshold voltage (below -55mV) however if a number of graded potentials sum together at the axon hillock this can lead to a suprathreshold value and and an action potential is generated. =
| | See [[Neuron|Neuron]] |
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| Neurones have a resting membrane potential (RMP), this is set up by a potassium ion leak channel. This allows potassium to move by [[Facilitated diffusion|facilitated diffusion]] from inside the cell out, down its concentration gradient, creating a slightly positive charge on the outside of the membrane compared to the inside. RMP is also set up by an [[ATP-ase|ATP-ase]] pump, sodium and potassium. This uses ATP to pump, against their concentration gradients, three sodium outside the cell and two potassium back in. This is a [[Symporter|symport]] protein channel. Both of these ion movements causes the inside of the cell to be slightly negative when compared to the outside, usually around -70mV. This is the resting membrane potential for a neurone.
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| <br> '''References''' === Mathews G. (2003) Cellular Physiology of Nerve and Muscle, 4th Edition, Oxford: Blackwell Pub.
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Latest revision as of 06:57, 27 November 2012