CBSE Class 10 Science 2019 · Paper 31/5/1 · Question 13
Why does the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron take place but not in the reverse direction ? Explain.
Answer
Only the axonal end releases chemicals and only the next neuron's dendritic end has receptors for them, so the signal cannot flow in reverse.
In a neuron the electrical impulse travels from the dendrite to the cell body and then along the axon to its end, the nerve ending. At the end of the axon the impulse sets off the release of some chemicals. These chemicals cross the gap, the synapse, and start a similar electrical impulse in the dendrite of the next neuron. The chemicals are released only at the axonal end, and only the dendritic end of the next neuron has receptors that respond to them; a dendrite releases no such chemicals. So a signal can cross the synapse only from the axon of one neuron to the dendrite of the next, never in the reverse direction: the flow is unidirectional.
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