Synaptic Communication- Chemical Synases Flashcards
Local recycling of synaptic vesicles
Process of quickly retrieving and refilling vesicles with neurotransmitters at the synapse for efficient neuron communication.
What does the voltage clamp method do?
Used to control and measure the membrane potential of a cell by holding it at a specific voltage while recording the resulting currents.
What happens in the control situation when you block current in sodium (Na+) and potassium (K+) channels?
Blocking Na+ and K+ channels reroutes current through Ca2+ channels, causing a slight delay before the chemical signal triggers an increase in the postsynaptic cell’s membrane potential.
Two experiments provide sufficient evidence that a rise in presynaptic Ca²⁺ concentration in triggering neurotransmitter release.
1) Microinjection of calcium into a squid giant presynaptic terminal triggers neurotransmitter release, even in the ABSENCE of presynaptic action potentials.
2) Microinjection of chealtor (Ca2+), into a squid giant presynaptic terminal PREVENTS transmitter release.
What determines the outcome of neurotransmitter (NT) release at the presynaptic terminal?
The strength of presynaptic activation.
How does low-frequency stimulation affect NT release?
Low-frequency stimulation reduces nerve cell activity, slowly increasing calcium levels near the synapse and promoting the release of small neurotransmitters.
Two Types of NT
1)Small-molecule neurotransmitters (amino acids, acetylcholine, purines and biogenic amines) -fast acting and directly bind to receptors
2) Neuropeptides- can act as neuromodulators with slower and more prolonged effects.
How does high-frequency stimulation affect NT release?
High-frequency stimulation increases the number of action potentials, elevating calcium levels broadly, leading to the release of both peptide and small-molecule neurotransmitters.
What determines whether neurotransmitter release is activated or inhibited?
Activation or inhibition is dependent on the local calcium gradient within the presynaptic terminal.
How is the SNARE complex related to calcium in neurotransmitter release?
Calcium activates the SNARE complex, which enables the fusion of synaptic vesicles with the cell membrane, leading to neurotransmitter release.
SNARE complex
Group of proteins that act like a bridge, connecting the vesicle and the cell membrane to make them fuse together and release neurotransmitters.
Synaptobrevin and Synaptotagmin function:
- Synaptobrevin is a protein involved in neurotransmitter release, located on synaptic vesicles
- Synaptotagmin is a calcium-binding protein that regulates synaptic vesicle fusion with the presynaptic membrane.
Correctly order the sequence of events involved in exocytosis during neurotransmitter release.(very smart elephants catch)
1)Vesicle docks
2) SNARE complexes form to pull membranes together.
3) Entering Ca²⁺ binds to synaptotagmin.
4) Ca²⁺-bound synaptotagmin catalyzes membrane fusion by binding to SNAREs and the plasma membrane.
Why don’t electrical synapses experience fatigue? And why do chemical synapses experience fatigue?
Electrical synapses avoid fatigue as they transmit signals directly through channels, while chemical synapses tire due to neurotransmitter depletion during signaling.
Differences between Chemical and Electrical Synapses
- Chemical synapses use neurotransmitters for signal transmission, while electrical synapses transmit signals directly through channels.
- Chemical synapses are more versatile with diverse neurotransmitters, while electrical synapses transmit signals faster but with less versatility.
Steps of Chemical Synapse Communication
- Synthesis of neurotransmitter
- Packaging of neurotransmitter
- Delivery to presynaptic terminal (if synthesized in cell body)
- Arrival of action potential to presynaptic terminal
- Influx of Ca2+ into presynaptic terminal
- Fusion of synaptic vesicles with presynaptic membrane
- Release of neurotransmitter
- Binding to receptor on postsynaptic membrane
- Response of postsynaptic membrane/cell
Clarithin
Protein involved in the endocytotic budding of vesicles from the plasma membrane
Correctly order the sequence of events involved in endocytosis during neurotransmitter release.(“Adorable Cats Don’t Always Have Vases”)
1) Adaptor proteins link clathrin to the vesicle membrane.
2) Clathrin proteins come together to form a coat, bending the membrane.
3) Dynamin forms a ring and pinches off the membrane.
4) Actin filaments move the coated vesicle.
5) Hsc-70 and auxilin remove the coat from the vesicle.
6) Vesicle fuses with endosomes or prepares for future neurotransmitter release.
Dynamin
Protein causes the final pinching-off of the membrane to create vesicles after neurotransmitter release.
Process of local recycling(“Every Ever Bear Really Does Prefer Eggs “)
- Exocytosis: Neurotransmitters are released into the synaptic cleft during an action potential.
- Endocytosis: Empty vesicle membranes are retrieved through endocytosis, forming new vesicles.
- Budding: Membrane proteins and lipids are retrieved, creating new synaptic vesicles.
- Recycling: New vesicles are reloaded with neurotransmitters.
- Docking: Reloaded vesicles attach to the presynaptic membrane.
- Priming: Vesicles become prepared for exocytosis.
- Exocytosis: Primed vesicles release neurotransmitters for communication.
Endocytosis vs Exocytosis:
Endocytosis is the process by which cells engulf substances from their surroundings by forming vesicles, while exocytosis is the opposite process, where vesicles fuse with the cell membrane, releasing their contents into the extracellular space.
