Coordination and response CIE A Level Biology revision | Baamboozle - Baamboozle

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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Where is the Z band?

In the middle of the I band

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Describe the structure of myosin

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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Why are muscle fibers not usually referred to as cells?

they are multinucleate

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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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What happens in the muscle fibers after the action potential is initiated?

depolarisation spreads down the T-tubules, channel proteins for Ca2+ open and Ca2+ ions diffuse out of the SR, bind to troponin

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What causes the conformational change in the troponin-tropomyosin complex

calcium ions attach to troponin

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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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What is the name of the endoplasmic reticulum of the muscle

sarcoplasmic reticulum

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