8 (a) Fig. 8.1 is a diagram of a motor neurone. [Figure 8.1]

1. (a)(i)Name cell X and part Y. X Y[2]
2. (a)(ii)Name a type of cell that forms a synapse with structure Z.[1]
3. (b)Table 8.1 shows some of the events that occur during muscle contraction. They are not listed in the correct order. Table 8.1 event description of event A calcium ions diffuse out of sarcoplasmic reticulum B myosin heads bind to actin C sarcolemma depolarised D sarcomere shortens E calcium ions bind to troponin F T-tubule system membranes depolarised G binding sites on actin exposed H myosin heads tilt I tropomyosin moves J troponin changes shape Complete Table 8.2 to show the correct order of the events that occur during muscle contraction. Two of the events have been completed for you. Table 8.2 correct order letter of event 1 2 3 4 5 J 6 7 8 9 10 D[4]
4. (c)Lambert-Eaton myasthenic syndrome (LEMS) is a rare disorder of the neuromuscular junction. A person with LEMS produces antibodies that bind to the voltage-gated calcium channels on the presynaptic knob. One symptom of LEMS is weaker muscle contraction. Suggest and explain why LEMS leads to weaker muscle contraction.[4]

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