The Synapse

Quick Answer: The Synapse is a synapse model: an enlarged view of the junction between two nerve cells, showing the presynaptic terminal with its vesicles of neurotransmitter, the narrow synaptic cleft and the receptors on the membrane of the next cell. It is used in biology, psychology and physiology lessons on how nerve signals pass from one neuron to the next.

Signalling Across the Synaptic Cleft

At most synapses neurons do not touch. The electrical impulse that runs along an axon stops at the presynaptic terminal, and the signal is carried across a gap of a few tens of nanometres by chemicals. When the impulse arrives, voltage-gated calcium channels open, calcium ions flow into the terminal, and vesicles packed with neurotransmitter fuse with the membrane and release their contents into the cleft by exocytosis.

The neurotransmitter diffuses across and binds to receptor proteins on the postsynaptic membrane. At an excitatory synapse the receptors let positive ions in and make the next neuron more likely to fire; at an inhibitory synapse they make it less likely. A single input is rarely enough, and the next neuron adds up many inputs over time and space, called summation, before an impulse is triggered. The signal is then ended quickly, either by enzymes that break the transmitter down or by transporter proteins that take it back into the presynaptic terminal for reuse. Because transmitter is released on one side and detected on the other, impulses cross a synapse in one direction only.

The listing does not state which structures this model shows or its magnification, and its product image is not currently available, so confirm these details. Many drugs work at synapses: some antidepressants block the reuptake of serotonin, and nicotine and caffeine act on receptors. The neuron model shows the whole nerve cell, and the Motor and Plate model shows the special synapse between nerve and muscle.

Lessons It Supports

• Teaching the sequence of events in synaptic transmission
• Explaining why impulses travel in one direction only
• Psychology and pharmacology lessons on drugs that act at synapses
• Comparing a synapse between neurons with the neuromuscular junction

Specifications

Care & Handling

• Handle the synapse model by its base; small raised vesicles and receptor shapes on the membranes can break off.
• Dust with a soft brush and clean marks with a lightly damp cloth.
• Keep it in a closed cupboard, away from sunlight and heat.

Why Choose LabEquip

Biology, psychology and physiology teachers use a synapse model because the chemical step between neurons is central to understanding learning, drugs and disease. LabEquip lists it in biology lab products; for structures and size, ask through the contact page.

Frequently Asked Questions

What is a synapse?

It is the junction where a nerve cell passes a signal to another cell, usually another neuron, a muscle fibre or a gland cell. At a chemical synapse the signal crosses a narrow gap as a neurotransmitter.

Why do nerve impulses cross a synapse in one direction only?

Neurotransmitter is stored and released only at the presynaptic terminal, and the receptors that detect it are only on the postsynaptic membrane. The signal can therefore pass only from the first cell to the second.

What role does calcium play at the synapse?

When an impulse reaches the terminal, calcium channels open and calcium ions flow in. The rise in calcium causes the vesicles to fuse with the membrane and release neurotransmitter into the cleft.

What is summation?

It is the adding together of signals at a synapse. Temporal summation is several signals arriving in quick succession from one neuron; spatial summation is signals arriving at the same time from several neurons. Either can reach the threshold for an impulse.

How is a neurotransmitter removed from the cleft?

Either an enzyme breaks it down, as acetylcholinesterase does with acetylcholine, or transporter proteins pump it back into the presynaptic terminal for reuse, as happens with serotonin and dopamine.

How do some antidepressants work at the synapse?

Selective serotonin reuptake inhibitors block the transporter that takes serotonin back into the presynaptic terminal. Serotonin stays in the cleft for longer and continues to act on the receptors.

Last Updated: September 2026