A-LevelBiologyControl and coordination9700/42 · Feb/Mar 2017 · Q79 Marks

(a) Most reflex arcs pass through the spinal cord and involve different types of neurones. Name and state the functions of the three types of neurone in a spinal reflex arc.

(a)Name and state the functions of the three types of neurone in a spinal reflex arc.[3]
(b)Some poisons affect the functioning of synapses between neurones. Listed below are four organisms, A, B, C and D, each of which produces a different poison that affects the functioning of synapses. A Hapalochlaena lunulata, the blue-ringed octopus B Conus textile, the textile cone sea snail C Clostridium botulinum, a bacterium D Physostigma venenosum, the calabar bean plant Table 7.1 summarises the action of the poisons from organisms A, B, C and D. [Table 7.1] Suggest and explain how poison from each of these organisms affects the functioning of synapses. A B C D[6]

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2017). The mark or mark type is shown in brackets.

[1] (a) sensory neurone – receives, input/impulses, from receptor;
[1] (a) relay/intermediate/internuncial, neurone – passes impulses on to motor neurone ;
[1] (a) motor neurone – sends impulses/output, to the effector;
[1] (b) six from: A: 1 Na+ cannot enter post-synaptic neurone ;
[1] (b) 2 no, depolarisation/action potential, (in post-synaptic neurone) ;
[1] (b) B 3 Ca2+ cannot enter pre-synaptic neurone ;
[1] (b) 4 vesicles cannot, move towards/fuse with, pre-synaptic membrane ;
[1] (b) C 5 ACh cannot be released ;
[1] (b) 6 into synaptic cleft;
[1] (b) D 7 ACh not broken down;
[1] (b) 8 continuous depolarisation/action potential, of post-synaptic neurone ;

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