CAIE IGCSE Biology 14.1.9 Events at a synapse
Practise sequencing neurotransmitter release, diffusion and receptor binding to explain how an impulse crosses a synapse.
- Syllabus
- 2026–2028
- Course
- Biology 0610
Practise sequencing neurotransmitter release, diffusion and receptor binding to explain how an impulse crosses a synapse.
Pregnancy can occur after the fusion of a male gamete and a female gamete.
Fig. 2.2 shows the junction between two neurones with drug X absent and two neurones with drug X present, immediately after a painful stimulus.

Fig. 2.2
Describe and explain how drug X affects the function of the relay neurone shown in Fig. 2.2.
any three from:
drug X blocks, D / receptor (molecules) ;
neurotransmitters are not able to bind to, D / receptor (molecules) ;
drug X is similar in shape to neurotransmitter / complementary to shape of receptor (molecule) ;
drug X stops, impulse/electrical signal, being transmitted in relay neurone ;
(so) less / no, pain felt with drug X ;