← Back to CoursesMolecular Neuroscience: Intermediate

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Synaptic Transmission: From Vesicles to Receptors

Manual: General · Subject: Molecular Neuroscience

Trace the molecular sequence that converts presynaptic activity into postsynaptic responses.

Chemical Synapses in Detail

Presynaptic Release

Neurotransmission begins when an action potential invades the presynaptic terminal and opens voltage-gated calcium channels. The resulting calcium influx triggers vesicle fusion through the synaptic release machinery.

Key Molecules

SNARE proteins
Drive vesicle membrane fusion
Synaptotagmin
Calcium sensor for exocytosis
Vesicular transporters
Load neurotransmitters into vesicles
Postsynaptic receptors
Convert chemical signals into cellular responses
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Core Sequence

Action potential ightarrow ightarrow calcium entry ightarrow ightarrow synaptic vesicle fusion ightarrow ightarrow transmitter release ightarrow ightarrow receptor activation ightarrow ightarrow postsynaptic response.

Which event directly triggers fast synaptic vesicle fusion?

What is one major difference between ionotropic and metabotropic receptors?

Postsynaptic Responses

Postsynaptic signaling can be excitatory or inhibitory depending on receptor type and ion selectivity. AMPA receptors produce fast excitatory currents, NMDA receptors are voltage- and ligand-dependent, and GABAA_A receptors typically mediate fast inhibition through Cl−Cl^- conductance.

Receptor Classes

Ionotropic

  • Fast millisecond responses
  • Direct ion channel function

Metabotropic

  • Slower modulatory effects
  • Activate G proteins and second messengers

How a Synapse Converts Signal to Response

  1. 1

    Step 1: Presynaptic depolarization opens calcium channels.

  2. 2

    Step 2: Calcium binds release machinery at docked vesicles.

  3. 3

    Step 3: Vesicles fuse with the membrane and release transmitter.

  4. 4

    Step 4: Neurotransmitter binds postsynaptic receptors.

  5. 5

    Step 5: Ionic or biochemical changes alter postsynaptic activity.

What best describes an ionotropic receptor?

Name one neurotransmitter commonly associated with fast excitatory transmission.