fibrous protein molecules anchored at the M line of a sarcomere each containing globular heads which point away from the M line
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15
What causes the conformational change in the troponin-tropomyosin complex
calcium ions attach to troponin
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15
Once Ca2+ binds to troponin what happens to allow muscle contraction?
Troponin tropomyosin moves to expose myosin binding sites on the actin filaments, myosin heads form cross-bridges with thin filaments and the sarcomere shortens
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15
What happens after acetylcholine diffuses into the synaptic cleft?
it binds with receptors on the sarcolemma causing Na+ channels to open and Na+ to diffuse in and depolarise the membrane and initiate an action potential
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15
What impact does the action potential have on the sarcoplasmic reticulum?
it opens calcium ion channels on the SR which causes calcium ions to floor the sarcoplasm.
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15
Why are muscle fibers not usually referred to as cells?
they are multinucleate
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15
Explain the events in the presynaptic neuron at the neuromuscular junction starting with the arrival of an action potential
diffusion of Ca2+ into neuron causes movement of vesicles containing acetylcholine which diffuses across the synapse to fuse with the presynaptic membrane
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15
What type of fibers are found in the A band?
myosin and actin
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Where is the Z band?
In the middle of the I band
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15
Describe the structure of actin?
globular protein molecules linked to form a chain which wrap to form a helical shape; tropomyosin is twisted around the two chains and troponin is also present
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15
What type of fibers are found in the H band?
Only myosin
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15
What is the name of the endoplasmic reticulum of the muscle
