Chemical Synapse Diagram Labeled

One synapse from the sending bulb to the receiving cell: 12 parts to name.

Chemical Synapse Diagram Labeled

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1 2 3 4 5 6 7 8 9 10 11 12
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Write the name of each numbered part.Answer key

  1. Presynaptic terminal
  2. Synaptic vesicle
  3. Mitochondrion
  4. Voltage-gated calcium channel
  5. Calcium ions
  6. Neurotransmitter
  7. Synaptic cleft
  8. Enzyme
  9. Reuptake transporter
  10. Neurotransmitter receptor
  11. Postsynaptic membrane
  12. Postsynaptic neuron

Drawn for this site by script, 2026-09-26. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the synapse on a muscle

All 12 parts on the diagram

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Start here: 6 main parts 6

  1. Presynaptic terminal The swollen end of the sending neuron's axon. Neurotransmitter is released here. Also called the synaptic end bulb.
  2. Synaptic vesicle A small sac of membrane packed with neurotransmitter, waiting to be released.
  3. Voltage-gated calcium channel Opens when an action potential arrives, letting calcium ions flow in. A channel in the presynaptic membrane.
  4. Neurotransmitter The chemical messenger released into the cleft. It binds to receptors on the next cell.
  5. Synaptic cleft The narrow gap between the two cells that the neurotransmitter crosses.
  6. Neurotransmitter receptor A protein on the postsynaptic membrane. The neurotransmitter binds to it, like a key in a lock.

The sending terminal: 5 2

  1. Mitochondrion Supplies the energy the terminal needs to make and recycle neurotransmitter.
  2. Calcium ions Calcium ions (Ca2+) that flow in through the channels. They make the vesicles fuse with the membrane.

In the cleft: 4 2

  1. Enzyme Breaks neurotransmitter down in the cleft. One of the ways it is cleared.
  2. Reuptake transporter Takes neurotransmitter back into the terminal, another way it is cleared. A protein in the presynaptic membrane.

The receiving cell: 3 2

  1. Postsynaptic membrane The membrane of the receiving cell, where the receptors sit.
  2. Postsynaptic neuron The receiving cell, here a neuron. A synapse can also be on a muscle or gland cell.

How this list was compiled: Read 2026-09-26. OpenStax Anatomy and Physiology 2e, section 12.5 Communication Between Neurons, https://openstax.org/books/anatomy-and-physiology-2e/pages/12-5-communication-between-neurons : the common parts of a synapse (presynaptic element, neurotransmitter packaged in vesicles, synaptic cleft, receptor proteins, postsynaptic element, neurotransmitter elimination or re-uptake); an action potential opening voltage-gated Ca2+ channels in the synaptic end bulb; Ca2+ making vesicles merge with the presynaptic membrane and release neurotransmitter by exocytosis into the synaptic cleft; neurotransmitter diffusing to receptors on the postsynaptic membrane, fitting like a key and lock; clearance by enzymatic degradation, neuronal reuptake or glial reuptake; the target cell not necessarily a neuron. Licence: own work

The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work

How it works

A chemical synapse diagram labeled from top to bottom: the sending terminal with its vesicles and calcium channels, the cleft the neurotransmitter crosses, and the receptors on the next cell. It answers the homework: correctly label the following parts of a chemical synapse.

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How the signal crosses

An action potential reaches the terminal and opens voltage-gated calcium channels. Calcium ions flow in and make synaptic vesicles fuse with the membrane, releasing neurotransmitter into the cleft. It crosses and binds to receptors on the postsynaptic membrane.

How it is cleared

The signal has to stop. An enzyme in the cleft can break the neurotransmitter down, or a reuptake transporter can carry it back into the terminal.

  • Pre comes before the gap, post comes after: at a chemical synapse the signal only runs one way.

Questions and answers

What is the synaptic cleft?

The narrow gap between the sending and receiving cells, which every chemical signal must cross. The neurotransmitter diffuses across it to reach the receptors.

What does calcium do at a synapse?

When an action potential arrives, calcium channels open and calcium ions flow into the terminal. The calcium makes the vesicles fuse with the membrane and release their neurotransmitter.

How is neurotransmitter removed from the synapse?

By enzymes that break it down in the cleft, or by reuptake into the sending neuron or nearby glial cells.

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