4- 'Life Cycle' of a Neurotransmitter Flashcards
What are precursors?
Small molecules which form the building blocks of neurotransmitters
Where are precursors obtained from?
Our diet
What happens after precursors are transported to the brain?
They are converted to neurotransmitters by enzymes
What are the 5 stages in the life cycle of a neurotransmitter?
- Uptake of precursors and synthesis
- Storage
- Release
- Receptor binding
- Deactivation
Where are small-molecule neurotransmitters created and what happens once they are?
Created at axon terminals, enzymes act on precursors
Where are neuropeptides made and where are they transported to?
Made in the endoplasmic reticulum and transported to the axon terminal for release
Where are neurotransmitters stored?
In vesicles
Where are small-molecule neurotransmitters packaged and maintained?
In synaptic vesicles
Where are neuropeptides packaged and stored, and transported to?
Packaged and stored in large dense-core vesicle
Transported to the axon terminal
What is the first stage of release?
Action potentials arrive at axon terminals
What happens after APs arrive at axon terminals?
Voltage-gated calcium channels open and calcium ions enter the cell, and calcium ions signal to the vesicles causing them to move to the membrane
How do vesicles release neurotransmitters?
By exocytosis
What happens once neurotransmitters have diffused across the synaptic cleft?
They bind to receptors
What are agonists?
Chemicals that bind to and activate a particular receptor
What is the principle of divergence?
Each neurotransmitter has many receptors, which can each have different effects
What do positive ions entering the cell cause?
An excitatory postsynaptic potential
What do negative ions entering the cell cause?
An inhibitory postsynaptic potential
What can an ionotropic receptor do?
It can open and close an ion channel
How does an ionotropic receptor work?
It changes membrane potential and shape to allow ions to move through
What are the effects of an ionotropic receptor like? (3 points)
Fast, local and short-term
What does a metabotropic receptor do?
Activates G protein when a neurotransmitter binds
What are effects of a metabotropic receptor like?
It takes a long time for effects to emerge
How do enzymes inactivate neurotransmitters?
By breaking them up into smaller fragments
