A synapse is the junction where a nerve impulse passes from one neuron to the next. NCERT defines it as the point "formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron, which may or may not be separated by a gap called synaptic cleft." Memory hook: think of it as a "handshake point" between two nerve cells, and the tiny gap in that handshake is the synaptic cleft.
A chemical synapse: the pre-synaptic axon terminal holds vesicles of neurotransmitter, which cross the fluid-filled synaptic cleft and bind to receptors on the post-synaptic membrane.
Your doubts, answered
Is the synaptic cleft the same thing as the synapse?
No. The synapse is the whole junction between two neurons. The synaptic cleft is only the small fluid-filled gap inside that junction. So the cleft is a part of the synapse, not the same as the synapse. In a chemical synapse the cleft is present; in an electrical synapse the two membranes are so close that there is almost no gap.
Does every synapse have a synaptic cleft?
No, and this is exactly what NCERT stresses with the words 'may or may not.' A chemical synapse has a clear synaptic cleft that separates the two neurons. An electrical synapse has the pre- and post-synaptic membranes in very close proximity, so there is no real gap. NEET often tests this 'may or may not be separated' phrase.
Which neuron is pre-synaptic and which is post-synaptic?
The pre-synaptic neuron is the one that sends the impulse; its axon terminal reaches the synapse first. The post-synaptic neuron is the one that receives the impulse next. Neurotransmitter receptors are on the post-synaptic membrane, so the signal always moves pre to post, never the other way in a chemical synapse.
What is present inside the synaptic cleft?
In a chemical synapse the cleft is a fluid-filled space. When an action potential reaches the axon terminal, synaptic vesicles fuse with the membrane and release neurotransmitters into this cleft. The neurotransmitters then cross the cleft and bind to receptors on the post-synaptic membrane.
Is a synapse only between two neurons?
Mostly, but the axon can also end at a neuro-muscular junction, where it meets a muscle. For your NCERT definition of a synapse, focus on the two-neuron junction: a pre-synaptic neuron and a post-synaptic neuron. The neuro-muscular junction is a related but separate term.
⚠️ The NEET trap ✗ Every synapse has a synaptic cleft separating the two neurons. ✓ A synapse may or may not have a synaptic cleft. A chemical synapse has a cleft; an electrical synapse has the membranes in very close proximity with no real gap. 🧠 NCERT's exact words are 'may or may not be separated by a gap called synaptic cleft.' NTA loves testing this phrase, so never assume a cleft is always present.
Real NEET questions
NEET 2017
Receptor sites for neurotransmitters are present on
A · Membranes of synaptic vesicles
B · Pre-synaptic membrane
C · Tips of axons
D · Post-synaptic membrane ✓
Solution: At a chemical synapse the arriving impulse triggers release of neurotransmitters into the synaptic cleft. These bind to specific receptors located on the post-synaptic membrane, which opens ion channels and generates a new potential. So the receptor sites are on the post-synaptic membrane.
NEET 2022
Select the incorrect statement regarding synapses:
A · The membranes of presynaptic and postsynaptic neurons are in close proximity in an electrical synapse.
B · Electrical current can flow directly from one neuron into the other across the electrical synapse.
C · Chemical synapse use neurotransmitters
D · Impulse transmission across a chemical synapse is always faster than that across an electrical synapse ✓
Solution: NCERT says impulse transmission across an electrical synapse is always faster than across a chemical synapse, because current flows directly between neurons. Chemical synapses add a delay due to neurotransmitter release, diffusion and receptor binding. So the claim that chemical is faster is the incorrect statement.
NEET 2026
The specific receptors for neurotransmitters in a synapse are present on __________.
A · Schwann cell
B · Pre-synaptic membrane
C · Myelin sheath
D · Post-synaptic membrane ✓
Solution: When an impulse reaches the axon terminal, synaptic vesicles fuse and release neurotransmitters into the synaptic cleft. These bind to their specific receptors present on the post-synaptic membrane, opening ion channels and generating a new potential. Thus the receptors are on the post-synaptic membrane.
Solved Neural Control and Coordination NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A synapse is the junction where a nerve impulse is passed from one neuron to the next. It is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron.
What is the synaptic cleft?
The synaptic cleft is the small fluid-filled gap between the pre-synaptic and post-synaptic membranes in a chemical synapse. Neurotransmitters cross this cleft to carry the signal.
What are the two types of synapses?
Electrical synapses and chemical synapses. In electrical synapses the membranes are very close and current flows directly. In chemical synapses a cleft separates the neurons and neurotransmitters carry the signal.
Where are neurotransmitter receptors located?
On the post-synaptic membrane. Released neurotransmitters bind to these receptors, open ion channels, and generate a new potential in the post-synaptic neuron. This is a repeated NEET point.
Which synapse is faster, electrical or chemical?
Electrical synapses are faster because current flows directly between neurons. Chemical synapses are slower due to neurotransmitter release, diffusion and binding. NEET 2022 tested exactly this.
