NEET 2026
- Exam
- NEET
- Year
- 2026
- Subject
- Biology
- Chapter
- Chapter
NEET 2026 · Biology · Chapter
When an artificial electrical stimulus is applied to the middle of...
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 neurotransmitter receptors.
- BThe synaptic cleft contains enzymes like acetylcholinesterase that actively push the neurotransmitters in a single direction.
- CGap junctions present at the chemical synapse allow the flow of ions strictly from the pre-synaptic to the post-synaptic neuron.
- 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 neurotransmitter receptors.
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-synaptic membrane lacks synaptic vesicles to release neurotransmitters and the pre-synaptic membrane lacks the receptors to receive them, the signal can only travel from the pre-synaptic neuron to the post-synaptic neuron.
Answer: The post-synaptic dendrites lack synaptic vesicles, and the pre-synaptic axon terminals lack specific neurotransmitter receptors.
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-synaptic membrane lacks synaptic vesicles to release neurotransmitters and the pre-synaptic membrane lacks the receptors to receive them, the signal can only travel from the pre-synaptic neuron to the post-synaptic neuron.
Answer: The post-synaptic dendrites lack synaptic vesicles, and the pre-synaptic axon terminals lack specific neurotransmitter receptors.