23 Turn over 9 Nicotine is a drug found in the smoke of cigarettes. (a) The flow diagram shows how the presence of nicotine can cause the release of noradrenaline. nicotine binds to acetylcholine receptors on the post‑synaptic membrane of a neurone action potential travels along the axon of the post‑synaptic neurone increased uptake of calcium ions by this neurone this neurone then releases noradrenaline (i) Explain how nicotine causes an action potential in the post-synaptic neurone that releases noradrenaline. 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(ii) State how an increase in calcium ion uptake by the neurone leads to the release of noradrenaline. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 24 (b) The effect of inhaling nicotine on the circulatory system of rats was investigated. In this investigation, three variables were considered: • the concentration of nicotine in blood plasma • the diameter of the lumen of one artery • blood pressure Two groups of rats were treated as shown in the table. Group Number of rats in group Nicotine dose / mg A 6 1.0 B 6 0.1 (i) The concentration of nicotine in the blood plasma of the group A rats was recorded at different times and the means calculated. The means are shown in the table along with the range of data for each mean. Time of sampling / minutes Mean concentration of nicotine in blood plasma / ng cm−3 0 (immediately after inhalation) 35.0 ± 9.3 30 (after inhalation) 24.1 ± 5.6 Determine the maximum rate of decrease in the concentration of nicotine in the blood plasma per minute after being given the nicotine. (2) Answer ............................................................................................. ng cm−3 min−1 25 Turn over (ii) The diameter of the lumen of one artery, in each of the 12 rats, was measured when the rats were resting. The blood pressure of each rat was also measured and the mean blood pressure calculated. The diameter of the lumen of the artery and the blood pressure of each rat were then recorded at intervals, for a total of 30 minutes. The rats inhaled nicotine for the first minute (0.0 to 1.0). The table shows the results for the mean diameter of the lumen of the artery. Time / minutes Mean diameter of lumen / µm Group A (1.0 mg nicotine) Group B (0.1 mg nicotine) 0.0 48 48 0.5 44 44 1.0 49 45 2.0 52 48 5.0 57 52 10.0 55 48 15.0 49 48 30.0 49 48 Determine the effect of nicotine concentration on the percentage change in lumen diameter in the first minute. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 26 *(iii) The graph shows the results for the mean blood pressure for the two groups of rats. Nicotine was inhaled for the first minute. 160 150 140 130 120 110 100 0 5 10 15 20 25 30 Time / minutes Mean blood pressure / mmHg Group A Group B It has been stated that: ‘Nicotine gained from smoking cigarettes in humans causes an increase in blood pressure and a decrease in the lumen of arteries.’ Analyse all the data from this investigation using rats to evaluate the validity of this statement. 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(Total for Question 9 = 14 marks)