The synapse: release, binding and termination
The anchor diagram of the course. Nearly every psychoactive drug changes one step of this cycle.
Where this fitsConnects to 2 · Unlocks 3
- Connects to
- The neuron and the action potential — Starts where the action potential arrives at the terminal.
- Receptor types: autoreceptors, heteroreceptors and location — The receiving side — receptors — gets its own chunk next module.
- Unlocks
- Norepinephrine and serotonin — and serotonin syndrome — SSRIs block the reuptake step; MAO inhibitors block the enzyme step.
- Locks and keys: receptor specificity, agonists and antagonists — Binding is where agonists and antagonists act.
- Dopamine: receptor families, clearance and pathways — Dopamine's transporter (DAT) and enzymes (MAO, COMT) are this cycle's termination step.
Orient
At the synapse, each AP releases ~1 vesicle into the synapse. NTs bind to receptors and then un-bind; they do not enter the post-synaptic neuron (but do cause ions to flow). The signal ends by reuptake into the pre-synaptic terminal, by enzymes that metabolize NTs, or by diffusion out of the synapse. Drugs act by changing release, binding or clearing.
Course terms
Your professor's wording, word for word from the slides. Learn the term and this definition — the explanation underneath is only there to help it make sense.
- Synaptic vesicles
“Membrane sacs in the neuron, which store transmitter molecules”Slides 02, p. 15
Released when an action potential arrives: ~1 vesicle per AP.
- Neurotransmitters
“Molecules released by neurons, which alter the activity of other cells”Slides 02, p. 15
Endogenous chemical messengers.
- Pre-synaptic / post-synaptic
“every neuron could be referred to as “pre-synaptic” and “post-synaptic” relative to whatever synapse we are currently referring to”Slides 02, p. 18
Pre-synaptic sends, post-synaptic receives — relative to the synapse you're talking about.
- Binding and un-binding
“NTs bind to receptors and then un-bind; they do not enter the post-synaptic neuron (but do cause ions to flow)”Slides 02, p. 20
Ion flow produces an EPSP or IPSP.
- Enzymes (signal termination)
“Enzymes that metabolize NTs can be found on post-synaptic membranes (AChE; COMT), inside pre-synaptic terminals (MAO), or inside adjacent glial cells (MAO; GABA-T)”Slides 02, p. 20
Where the enzyme sits changes how a drug that blocks it works.
- Vesicular transporters
“packaged back into vesicles by vesicular transporters”Slides 02, p. 20
After reuptake, NTs are repackaged into vesicles; the reuptake transporter itself does not become a vesicle.
From your course: Course slides 02, pp. 19–20 · Course slides 03, p. 2
Tip: the ← and → keys move through the lesson.
Full lesson: Synaptic release · Signal termination