Biology 9700/42 — October/November 2012
Cambridge A-Level · A Level Structured Questions · worked solutions for every part, with the mark scheme
Topics Inheritance · Control and Coordination · Selection and Evolution · Genetic Technology · (outdated) Biotechnology · (outdated) Aspects of Human Reproduction · +4 more
Nerve impulses have to cross synapses. The events that enable a nerve impulse to cross a cholinergic synapse are listed in Table 1.1.
The events are not listed in the correct order.
Table 1.1
| event | description of event |
|---|---|
| A | Calcium ions enter presynaptic neurone knob. |
| B | Acetylcholine binds to receptor proteins on postsynaptic membrane. |
| C | Vesicles fuse with presynaptic membrane and release acetylcholine into synaptic cleft. |
| D | Postsynaptic membrane becomes depolarised. |
| E | Nerve impulse reaches presynaptic membrane. |
| F | Acetylcholine diffuses across cleft. |
| G | Receptor proteins change shape, channels open and sodium ions enter postsynaptic neurone. |
| H | Calcium ion channels open in presynaptic membrane. |
| I | Nerve impulse generated in postsynaptic neurone. |
| J | Vesicles of acetylcholine move towards presynaptic membrane. |
Complete Table 1.2 to show the events in the correct order.
Two of the events have been done for you.
Table 1.2
| correct order | letter of stage |
|---|---|
| 1 | E |
| 2 | |
| 3 | |
| 4 | |
| 5 | |
| 6 | F |
| 7 | |
| 8 | |
| 9 | |
| 10 |
Synapses have many roles in nervous coordination in mammals.
Explain how synapses ensure one-way transmission of nerve impulses.
In a learning activity, it is believed that the number of synapses between neurones increases.
Suggest the advantages of this increased number of synapses.
The rest of this paper
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