A synapse is a specialized junction between two neurons where they communicate. It consists of three parts: (1) the axon terminal of the presynaptic (sending) neuron, (2) the synaptic cleft (a ~20 nm gap), and (3) the membrane of the postsynaptic (receiving) neuron. Signals are transmitted chemically via neurotransmitters.
A synapse is the junction between two neurons where they communicate. The signal travels from the axon terminal of one neuron (presynaptic) across a tiny gap (synaptic cleft) to the dendrite of the next neuron (postsynaptic). The message is chemical: neurotransmitters (small molecules like acetylcholine, dopamine, serotonin) carry the signal across the gap. Understanding synaptic transmission is key to understanding how the nervous system processes and transmits information.
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Neurotransmitters are small chemical molecules (acetylcholine, dopamine, serotonin, GABA, glutamate, etc.) stored in synaptic vesicles. When an action potential arrives at the axon terminal, vesicles fuse with the membrane and release neurotransmitters into the synaptic cleft. These molecules diffuse across and bind to specific receptors on the postsynaptic membrane, triggering a response.
An excitatory synapse increases the likelihood that the postsynaptic neuron will fire an action potential (typically via depolarization). An inhibitory synapse decreases this likelihood (typically via hyperpolarization). The same neurotransmitter can be excitatory or inhibitory depending on the postsynaptic receptor type.
The synaptic cleft provides a safety barrier and allows for signal amplification, filtering, and modulation. Chemical transmission is also more flexible — the same neurotransmitter can have different effects via different receptors, and the signal can be fine-tuned by multiple factors.
After binding to postsynaptic receptors, neurotransmitters are either (1) reabsorbed by the presynaptic terminal (reuptake), (2) reabsorbed by glial cells, or (3) broken down by enzymes. This rapid removal is crucial for temporal precision of neural signaling and allows the synapse to respond to new signals.
Visualize synaptic transmission — neet explained with an interactive 3D simulation.
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