Synaptic Transmission and Plasticity Flashcards
What is meant by “classical” synaptic transmission?
Neurotransmitters are released from the presynaptic terminal to directly apposed receptors on the post-synaptic site of another neuron
What is meant by the term “extrasynaptic transmission”?
A neurotransmitter is released that binds to distant postsynaptic receptors outside the synaptic terminal
What is electrical synaptic transmission?
Communication between neurons coupled by gap junctions; very fast
How can you tell what part of the neuron is a dendrite?
Dendrites have spines
True or false: dendrites on the same neuron only incorporate information from one part of the brain.
False - they can incorporate information from multiple parts of the brain
Describe the process of neuron and synapse development (general, 3 steps)
Where are inhibitory synapses located on a neuron?
Close to the shaft (axon hillock) of the neuron so that the receiving neuron is able to respond to the input more quickly
[…] neurons usually have spines whereas […] neurons usually do not
Excitatory, glutaminergic
Inhibitory, GABAergic
Describe the process of synaptic transmission.
- An action potential is generated due to an increase in intracellular [Na+] that causes the RMP to reach the threshold -55mV
- The AP travels down the axon to the pre-synaptic terminal. When it reaches the PST, it opens voltage gated Ca2+ channels which leads to influx of Ca2+ into the pre-synaptic neuron.
- Increased Ca2+ helps traffic vesicles containing neurotransmitters to the synapse.
- Vesicles fuse with the membrane of pre-syanptic neuron and release contents into cleft
- NT binds to receptors on post-synaptic neuron membrane.
- NT binding leads to EPSP or IPSP. If an EPSP and it is sufficient enough to cause the neuron to reach threshold, an AP will occur.
- NT unbinds leaves cleft by any of several mechanisms (diffusion, reuptake, enzymatic degradation, astrocytes).
What are the means by which a neurotransmitter can be cleared from a synapse?
Describe how ionotropic receptors on post-synaptic neurons work.
The neurotransmitter binds to its receptor on the post-synaptic neuron. This causes a conformational change in an adjacent ion channel that allows ions to enter the post-synaptic neuron.
Describe how metabotropic receptors on post-synaptic neurons work.
Neurotransmitter binds to receptor on post-synaptic neuron, which causes conformational change on internal side of receptor, which triggers a second messenger cascade (i.e. GPCR) whose downstream effect is movement of ions in or out of the cell.
True or false: Ionotropic receptors result in fast synaptic transmission while metabotropic receptors result in slow synaptic transmission.
True
In an excitatory synapse, […] ions enter the post-synaptic neuron in response to neurotransmitter binding.
In an inhibitory synapse, […] ions enter the post-synaptic neuron in response to neurotransmitter binding.
Na+
Cl-
Describe the process of excitatory synapse formation.
Describe how AMPA receptors work.
AMPA receptors are ligand gated ion channels for Na+. When glutamate binds to AMPA, there is a conformational change in the receptor that opens the receptor and allows Na+ to enter the post-synaptic neuron. This results in a moderate local depolarization. This this depolarization reaches threshold or is accompanied by other signals to depolarize from other AMPA receptors, an AP can be generated.
Describe how NMDA receptors work.
NMDA receptors are both ligand and voltage gated and have a molecule of Mg2+ blocking their channel. As such, they first must have glutamate bind to them. Then, they require a small depolarization in order to pop off the Mg2+ to allow entry of Na+ and Ca2+. This small depolarization is often provided by a neighboring AMPA receptor, so the two work together. The Ca2+ that enters the cell can then trigger second messaging cascades in the neuron.
Describe how mGluRs work.
Glutamate binds to mGluR –> activates Gaq –> activates PLC –> cleaves PIP2 to DAG and IP3 –> IP3 binds to receptor in ER causing release of intracellular Ca2+ to cytosol to increase Ca2+ inside neuron.
What is Hebb’s postulate?
Neurons that fire together wire together
How is long term potentiation developed?
Brief bursts of high - frequency stimulation excitatory input at glutamatergic synapses causes the amplitude of EPSPs to increase and remain increased after the stimulus has been removed. In this manner, synapses that undergo these stimuli are strengthened and those that don’t are unaffected. Proteins are needed to maintain LTP strength.
Describe how long term potentiation occurs.
High-frequency excitatory stimuli that result in the release of glutamate from pre-synaptic neurons. Glu then binds to AMPA and NMDA receptors on post-synaptic neurons. If this binding leads to activation of a lot of NMDA receptors, then a lot of Ca2+ can enter the post-synaptic neuron and this can result in the triggering of cascades that result in protein phosphorylation and increase in AMPA receptors being inserted into the membrane.
Describe how long term depression occurs.
Excitatory stimuli result in the release of glutamate from pre-synaptic neurons. Glu then binds to AMPA and NMDA receptors on post-synaptic neurons. If this binding leads to activation of only a small amount of NMDA receptors, then a smaller amount of Ca2+ can enter the post-synaptic neuron and this can result in the triggering of cascades that result in protein dephosphorylation and decrease in AMPA receptors via receptor internalization.
True or false: LTD only occurs via NMDA receptor activation.
False - it can also occur via mGluR receptor activation.
