NEET2026BiologyChapterActual
When an artificial electrical stimulus is applied to the middle of an axon, the action potential propagates in both directions along the membrane. However, at a chemical synapse, the signal can only be transmitted forward to the next neuron. Which of the following best explains this one-way transmission?
Options
- AThe post-synaptic dendrites lack synaptic vesicles, and the pre-synaptic axon terminals lack specific neurotra
- BThe synaptic cleft contains enzymes like acetylcholinesterase that actively push the neurotransmitters in a si
- CGap junctions present at the chemical synapse allow the flow of ions strictly from the pre-synaptic to the pos
- DThe pre-synaptic membrane is completely impermeable to calcium ions, preventing any backward signal generation
Correct answer
A. The post-synaptic dendrites lack synaptic vesicles, and the pre-synaptic axon terminals lack specific neurotra
Step-by-step solution
At a chemical synapse, the transmission of a nerve impulse is unidirectional. This is because the neurotransmitters are stored in synaptic vesicles which are exclusively present in the pre-synaptic axon terminals. When an action potential reaches the axon terminal, these vesicles release neurotransmitters into the synaptic cleft. The specific receptors that bind to these neurotransmitters are located only on the post-synaptic membrane (usually on dendrites or the cell body of the next neuron). Since the post-synapt