Synaptic Transmission and Electrical Synapses

These flashcards cover key concepts, terminology, and mechanisms concerning synaptic transmission and electrical synapses as discussed in the lecture.

What are electrical synapses characterized by?

Rapid (essentially instantaneous) postsynaptic response.

What is the primary function of chemical synapses?

Transmission of signals using neurotransmitters.

What key feature distinguishes electrical synapses from chemical synapses?

Electrical synapses allow direct current flow through gap junctions.

What structures link adjacent cells in electrical synapses?

Gap junctions.

What type of channels do receptors in direct chemical transmission utilize?

Ligand-gated ion channels.

What are gap junction channels formed from?

Two hemichannels meeting in the extracellular space.

What kind of proteins form gap junctions in vertebrates?

Connexins.

How do electrical synapses differ in connection speed compared to chemical synapses?

Electrical synapses are much faster.

Which channel allows for the flow of small molecules and ions through gap junctions?

Connexons.

What may influence the strength of a synaptic connection?

The relative size of the involved cells.

What is the term for the ability to modify synaptic strength over time?

Plasticity.

What two families of proteins construct gap junction channels?

Connexins and pannexins.

What happens when voltage-sensitive gates are activated in gap junctions?

They may allow current flow in only one direction.

What type of neurotransmitter signaling is slower and temperature sensitive?

Chemical synaptic transmission.

What current flows through electrical synapses?

Ionic current.

What role do astrocytes play in the synaptic environment?

Regulate neurotransmitter availability and recycling.

What occurs during the fusion of synaptic vesicles?

Release of neurotransmitters into the synaptic cleft.

What is the distance between connexons in gap junctions that is a key feature?

About 2-4 nm.

What type of synapse uses chemical neurotransmitters?

Chemical synapse.

What ion's influx is primarily responsible for neurotransmitter release?

Calcium (Ca2+).

What are the main cell types found in electrical synapses?

Neurons and glial cells.

What did the crayfish tail flip demonstrate regarding electrical synapses?

Rapid transmission of signals for motor responses.

What happens when synaptic vesicles release neurotransmitters?

They diffuse across the synaptic cleft.

Which receptors are activated by neurotransmitters in chemical synapses?

Postsynaptic receptors.

What determines the directionality of signal flow in rectifying electrical synapses?

The resistance of the presynaptic and postsynaptic cells.

In the context of electrical synapses, what does RC stand for?

Coupling resistance.

How is the coupling ratio calculated?

ΔVpost / ΔVpre.

What do chemical synapses typically involve as part of their structure?

Synaptic vesicles containing neurotransmitters.

What must occur for synaptic transmission to take place?

Fusion of synaptic vesicles with the presynaptic membrane.

How are electrical synapses typically compared to chemical synapses?

More rapid information transfer.

What is a characteristic feature of gap junctions in the context of cellular communication?

Permeable to ions and small molecules.

What happens to neurotransmitter concentrations after their release?

They are degraded or taken back up by the presynaptic cell.

What type of synapse might ensure redundancy during signal transmission?

Electrical synapse.

What allows neurons in certain pathways to transmit signals almost instantaneously?

Electrical synapses.

What does the term 'synaptic cleft' refer to?

The space between adjacent neurons at a synapse.

What is a defining physiological characteristic of rectifying electrical synapses?

One-way flow of signals.

What is essential for initiating synaptic vesicle release?

An action potential arriving at the presynaptic terminal.

How do synaptic vesicles release their contents?

Through a process called exocytosis.

What can increase the rate of synaptic transmission?

Higher frequency of action potentials.

What role do voltage-gated Na+ channels play in synaptic transmission?

They initiate action potentials in the presynaptic neuron.

What is the significance of the synaptic gain in electrical synapses?

Determines how effectively a signal is transmitted.

What do ligand-gated ion channels respond to?

Binding of neurotransmitters.

What occurs at the postsynaptic cell following neurotransmitter binding?

Opening of ion channels resulting in synaptic potentials.

What are the anatomical correlates of electrical synapses?

Gap junctions consisting of connected hemichannels.

What is fundamental about the coupling between neurons in an electrical synapse?

Direct current flow allows rapid signaling.

In the frog neuromuscular junction, what is the role of acetylcholine?

It activates receptors on the muscle fiber, leading to contraction.

What experimental systems have been used to study synaptic transmission?

Frog neuromuscular junction and squid giant synapse.

How are neurotransmitters inactivated after synaptic transmission?

Through enzymatic breakdown or reuptake by transporters.

What technique was critical for early studies of synaptic transmission?

Histological staining methods for visualizing synapses.

What method allows researchers to analyze the function of individual synapses?

Electrophysiological recordings.