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

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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

Why are muscle fibers not usually referred to as cells?

they are multinucleate

What type of fibers are found in the A band?

myosin and actin

What type of fibers are found in the I band?

Only actin

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

Where is the Z band?

In the middle of the I band

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

What is the name of the endoplasmic reticulum of the muscle

sarcoplasmic reticulum

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

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.

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

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

What causes the conformational change in the troponin-tropomyosin complex

calcium ions attach to troponin

What type of fibers are found in the H band?

Only myosin

Coordination and response CIE A Level Biology re ...