Nerve/synapse IV Flashcards
We can model synaptic plasticity experimentally using […]
Long-term potentiation (LTP)
Explain what happens during LTP during the control phase.
A single action potential is stimulated in the presynaptic terminal. Both the AMPA and the NMDA receptors open, but the NMDA receptors remain blocked by magnesium. So some Na+ flows through the AMPA and creates a bit of depolarization.
Explain what happens during LTP in the induction phase.
Several action potentials are sent in a row, so EPSPs start accumulating. The postsynaptic terminal will eventually become depolarized enough that the NMDA receptors will open, allowing Ca2+ to flow in. This will activate intracellular signalling molecules and cause the postsynapstic terminal to become potentiated (made stronger)
What is the effect of induction on EPSPs in LTP?
It will cause them to last longer, as the synapse has become stronger. This leads to more AMPA receptors on the postsynaptic membrane, allowing the cell to become depolarized more easily when a single action potential is sent through again.
What happens when concentrations of glutamate are too high in a neuron?
It leads to a phenomenon called excitotoxicity. Too much glutamate is toxic to neurons.
What is the cause of excitotoxicity?
Too much glutamate flowing into the neuron means that the NMDA and AMPA receptors are staying active. So lots of sodium and especially calcium flow in. Too much calcium is bad for cells, so the neuron will recognize this and kill itself.
What is the effect of excitotoxicity?
It contributes to neuronal degeneration after stroke and in some neurodegenerative diseases.
What is the purpose of inhibitory synapses?
They make a neuron less likely to fire an action potential by hyperpolarizing the membrane. They also affect the pattern of action potential firing.
What is the main inhibitory neurotransmitter? Where is it found (prior to action potential)
GABA. It is found packaged in the presynaptic vesicles.
What post-synaptic receptors are responsible for GABA? Describe them.
GABA(A) receptors, which are ion channels similar to AMPA and NMDA receptors.
The GABA(A) receptor is a(n) […] receptor
Ionotropic
Explain the function of the GABA(A) receptor.
When it is activated by GABA, it opens up to Cl-, which hyperpolarizes the postsynaptic membrane, making the neuron less likely to fire an action potential.
What is the most common target for therapeutic compiunds like valium and xanax?
GABA(A) receptors are important targets for these compounds. These drugs bind to the receptor and make it more sensitive to GABA, making inhibitory synapses work better. This is why they might make the user sleepy.
Where are excitatory and inhibitory inputs located on a given neuron?
Excitatory inputs tend to be located on dendritic spines, while inhibitory neurons are often clustered on or near the cell soma to maximize their effect.
Whether or not a neuron fires an action potential depends on […]
The balance of EPSPs and IPSPs.
