Week 3: The Synapse Flashcards
What is the first neuron of transmission called?
Presynaptic neuron
What is the target cell of transmission called?
Postsynaptic neuron
How do electrical synapses work?
Ions flow from cytoplasm of one neuron direct to cytoplasm of target neuron through connexons (gap junction channels)
What are some advantages of electrical synapses?
- Bidirectional
- Useful for fast transmission and synchronising neural activity
- Simpler than chemical synapses
What are the basic steps of transmission?
- Neurotransmitter synthesis
- Load to neurotransmitter into synaptic vesicles
- Vesicles fuse to presynaptic terminal and NTs released
- Neurotransmitter (NT) molecules flow into synaptic cleft
- NT binds to postsynaptic receptors
- Biochemical/electrical response to postsynaptic cell
- Removal of NT from synaptic cleft
What are the three groups which NTs can be classified into?
- Small-molecule transmitters
- Peptide transmitters
- Transmitter gases
What happens during synthesis and storage (stage 1 & 2)?
Neurotransmitters are synthesised and stored in vesicles located in the presynaptic axon terminal
What happens during release (stage 3)?
Action potential arrives and transmitter is released across the presynaptic membrane by exocytosis (Ca2+ ions)
What happens during binding (stage 4)?
Neurotransmitter travels across synaptic cleft and binds with receptor proteins
What happens during triggering (stage 5 & 6)?
- Ion channels open receptor channels to allow ions to flow through postsynaptic membrane for depolarisation and hyperpolarisation
- Small G-proteins are activated to trigger metabolic processes in the neuron
What happens during removal (stage 7)?
- NT may diffuse away
- Enzymes in the cleft inactivate/metabolise the NT
- Reuptake pumps may pump NT back into presynaptic axon terminal for destruction or reloading into vesicles
What are vesicles?
Small membrane-enclosed spheres containing neurotransmitters
What are secretory granules?
Large vesicles containing peptides
What are peptides?
A short chain of amino acids stored in secretory granules
What is the Neuromuscular Junction?
Synapse between motor neuron and muscle
