Friday 14 June 2024 Morning Time allowed: 2 hours Materials For this paper you must have: • a ruler with millimetre measurements • a scientific calculator. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Show all your working. • Do all rough work in this book. Cross through any work you do not want to be marked. Information • The marks for the questions are shown in brackets. • The maximum mark for this paper is 91. Answer all questions in the spaces provided. box 0 1 Figure 1 shows a drawing of a neuromuscular junction. Figure 1 0 1 . 1 Name the parts labelled A to D. [2 marks] A B C D 3 *03* Turn over ► IB/M/Jun24/7402/2 Do not write outside the 0 1 box . 2 Following the release of acetylcholine into a neuromuscular junction, a muscle contraction occurs. Describe the sequence of events, following the release of acetylcholine, that leads to stimulation of this contraction. Do not include in your answer the events following the release of calcium ions in the myofibril. [4 marks] 0 1 . 3 Inhibitory synapses cause hyperpolarisation in postsynaptic neurones. Explain how this inhibits synaptic transmission. [2 marks] 8 4 *04* IB/M/Jun24/7402/2 Do not write outside the 0 2 box . 1 Figure 2 shows part of a relaxed myofibril. Figure 2 The myofibril represented in Figure 2 has 34 sarcomeres. The length of every sarcomere is 2 µm After contraction of this myofibril, the length of each sarcomere changed by 20%. Use the information provided to calculate the length of the myofibril after contraction. Give your answer in mm and in standard form. Show your working. [2 marks]