Muscle

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= Skeletal muscle  =
 
= Skeletal muscle  =
  
A skeletal muscle muscle consists of muscle fibres. One muscle fibre is approximatels 100 µm in diameter and consists of several [[Nucleus|nuclei]] and many [[Mitochondria|mitochondria]]. Each muscle fibre contains [[Myofibril|myofibrils]]. These are approximately 1 µm in diameter.<br>  
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A skeletal muscle muscle consists of muscle fibres. One muscle fibre is approximatels 100 µm in diameter and consists of several [[Nucleus|nuclei]] and many [[Mitochondria|mitochondria]]. Each muscle fibre contains [[Myofibril|myofibrils]]. These are approximately 1 µm in diameter.<br>
  
 
The [[Myofibril|myofibril]] is organised in repating units called [[Sacromeres|sacromeres]]. These contain thick and thin filaments. Muscle contraction occurs when the thin filaments slide along the thick filament by hydrolysing [[ATP|ATP]]&nbsp;<ref>Berg J., Tymoczko J and Stryer L. (2001) Biochemistry, 5th edition, New York: WH Freeman.</ref>&nbsp;by what is known as the [[The Sliding Filament Theory|Sliding Filament Theory]].  
 
The [[Myofibril|myofibril]] is organised in repating units called [[Sacromeres|sacromeres]]. These contain thick and thin filaments. Muscle contraction occurs when the thin filaments slide along the thick filament by hydrolysing [[ATP|ATP]]&nbsp;<ref>Berg J., Tymoczko J and Stryer L. (2001) Biochemistry, 5th edition, New York: WH Freeman.</ref>&nbsp;by what is known as the [[The Sliding Filament Theory|Sliding Filament Theory]].  
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Contraction in a muscle cell&nbsp;is produced&nbsp;by an [[Action_potential|action potential ]]travelling along a motor neurone and arriving at a [[synapse]]. The voltage gradient causes voltage-gated calcium [[Ion_channels|ion channels]] in the [[presynaptic|presynaptic ]]neurone to open, triggering [[Vesicles|vesicles]] containing [[Neurotransmitter|neurotransmitters]], specifically acetylcholine, to travel towards the [[sarcolemma|sarcolemma]]; fusing with the membrane and&nbsp;releasing acetylcholine into the [[synaptic cleft|synaptic cleft ]]<ref name="null">Bowness E, Braid K, Brazier J, Burrows C, Craig K, Gillham R, Towle J. (2009), A2-level Biology The Revision Guide Exam Board AQA, page 57, Newcastle-upon-Tyne: CGP books.</ref>. They diffuse across the cleft where they bind to specific [[Receptor|receptors]] called nicotinic cholinergic receptors, on the sarcolemma, where the [[depolarisation|depolarisation]] travels along the membrane and deep into the cell via [[T-tubules|T-tubules ]]<ref name="null">Bowness E, Braid K, Brazier J, Burrows C, Craig K, Gillham R, Towle J. (2009), A2-level Biology The Revision Guide Exam Board AQA, page 58 -60, Newcastle-upon-Tyne: CGP books.</ref>. Therefore it allows the [[sarcoplasmic reticulum|sarcoplasmic reticulum]] to become depolarised, releasing calcium ions and triggering muscle contraction to take place by the [[The_Sliding_Filament_Theory|sliding filament theory ]]<ref>Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P. (2008), Molecular Biology of The Cell, page 1028-1029, 5th edition, New York:Garland Science.</ref>.
  
 
=== References  ===
 
=== References  ===
  
 
<references />
 
<references />

Revision as of 15:13, 14 December 2010

Skeletal muscle

A skeletal muscle muscle consists of muscle fibres. One muscle fibre is approximatels 100 µm in diameter and consists of several nuclei and many mitochondria. Each muscle fibre contains myofibrils. These are approximately 1 µm in diameter.

The myofibril is organised in repating units called sacromeres. These contain thick and thin filaments. Muscle contraction occurs when the thin filaments slide along the thick filament by hydrolysing ATP [1] by what is known as the Sliding Filament Theory.


Contraction in a muscle cell is produced by an action potential travelling along a motor neurone and arriving at a synapse. The voltage gradient causes voltage-gated calcium ion channels in the presynaptic neurone to open, triggering vesicles containing neurotransmitters, specifically acetylcholine, to travel towards the sarcolemma; fusing with the membrane and releasing acetylcholine into the synaptic cleft [2]. They diffuse across the cleft where they bind to specific receptors called nicotinic cholinergic receptors, on the sarcolemma, where the depolarisation travels along the membrane and deep into the cell via T-tubules [2]. Therefore it allows the sarcoplasmic reticulum to become depolarised, releasing calcium ions and triggering muscle contraction to take place by the sliding filament theory [3].

References

  1. Berg J., Tymoczko J and Stryer L. (2001) Biochemistry, 5th edition, New York: WH Freeman.
  2. 2.0 2.1 Bowness E, Braid K, Brazier J, Burrows C, Craig K, Gillham R, Towle J. (2009), A2-level Biology The Revision Guide Exam Board AQA, page 57, Newcastle-upon-Tyne: CGP books.
  3. Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P. (2008), Molecular Biology of The Cell, page 1028-1029, 5th edition, New York:Garland Science.
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