(a) Fig. 7.1 is a diagram representing a synapse between a chemoreceptor cell from a human taste bud and a dendrite of a sensory neurone. [Figure 7.1]

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2023). The mark or mark type is shown in brackets.

1. [4] (a) any four from:
2. [4] (a) 1 0.1 g dm⁻³ chemoreceptor (membrane), is not depolarised / does not release neurotransmitter / remains at resting potential ;
3. [4] (a) 2 so, dendrite / sensory neurone, is not depolarised / remains at resting potential / has no action potential;
4. [4] (a) 3 1.0 g dm⁻³/ 10.0 g dm⁻³, chemoreceptor (membrane), is depolarised / releases neurotransmitter ;
5. [4] (a) 4 so, depolarisation / action potential / impulse, in, dendrite / sensory neurone ;
6. [4] (a) 5 receptor/generator, potential qualified ;
7. [4] (a) 6 ref. to threshold / all or nothing law (in context of either cell) ;
8. [3] (b) any three from:
9. [3] (b) sensory | motor
10. [3] (b) 1 cell body, between dendron and axon / in ganglion | and cell body, at end / in CNS ;
11. [3] (b) 2 has dendron and axon | and has (long) axon ;
12. [3] (b) 3 no dendrites from cell body | and dendrites extend from cell body ;
13. [3] (b) 4 carries impulses from receptor to, CNS / intermediate neurone | and carries impulses from, CNS / intermediate neurone, to effector;