#5 Flashcards
How does Long term potentiation (LTP) work?
LTP means model of synaptic plasticity
- Add electrode into postsynaptic neuron to record EPSPs, and add an electrode into the presynaptic axon to stimulate action potentials 2. Stimulate one action potential, leading to a small EPSP 3. Stimulate a series of action potentials (-100/sec), leading to depolarisation of the postsynaptic spine, removing the Mg2+ block from the NMDA receptors, and allowing for the conduction of Ca2+ a. This leads to a large depolarisation in steps, allowing for the influx of Ca2+ into the cell 4. Stimulate one action potential, and notice that the EPSPs are larger and longer lasting
hy did post synaptic cell make larger EPSPs?
postsynaptic spine inserts more AMPA receptors into post synaptic cell; same amount of glutamate, but more receptors
Glutamate toxicity
High concentrations of glutamate are toxic to neurons
This phenomenon, called excitotoxicity, is thought to involve calcium influx through NMDA receptors
What happens if receptors are overly activated by glutamate?
if receptors are overly activated by glutamate, neuron gets overexcited, too more calcium flows in
What happens If calcium concentration goes up too high ?
If calcium concentration goes up too high and stays high, neuron undergoes apoptosis in order to protect other neurons
This is associated with neuropathological disorders - Contributes to neuronal degeneration after stroke
what problems arise from drugs that block NMDA receptors?
causes hallucinations
Two types of synapses
Excitatory Synapse, located on the spine. Excitatory synapses responsible for action potentials. (AMPA receptors) NMDA receptors, responsible for synaptic plasticity, strengthening active synapses. Inhibitory Synapse, located on shafts.
Inhibitory Synapse: - Why do we need them?
- Makes neuron less likely to fire an action potential, i.e., keeps things under control - They determine the pattern of action potential firing in neurons
Neurotransmitters released by?
Neurotransmitters released by presynaptic terminals are called GABA.
what are GABA_A receptors?
Postsynaptic receptors are called GABA_A receptors. GABA_A is an ionotropic receptor. Activated GABA_A receptor is permeable to Cl- which when flows inside the postsynaptic dendrite, hyperpolarizes the postsynaptic dendrite. (IPSP). - This makes the neuron less likely to fire an action potential
Why are GABA_A receptors important?
GABAA receptors are important channels for medications or drugs Valium and Xanax bind to receptor, they don’t open channel. but they make the channel more sensitive to GABA This is why these medications make you tired Ethanol (alcohol) also works on GABAA IPSP makes the postsynaptic neuron to be less likely to fire an action potential.
What do Inhibitory synapses do?
Inhibitory synapses keep excitatory synapses under control, preventing excitatory synapses going out of control which can cause epilepsy seizures. Inhibitory synapses are closer to the initial segment, they have a bigger effect than excitatory synapses to determine whether or not the neuron fires an action potential.
Inhibitory vs Excitatory Neurons
Neurons are either excitatory or inhibitory. Inhibitory neurons tend to have short axons, excitatory tend to have longer axons Inhibitory neurons have a more local effect, excitatory neurons relay information all over the body Inhibitory neurons still have excitatory synapses on their dendrites.
Metabotropic Receptors (G-protein coupled receptors (GPCRs)) activated by?
These receptors are also activated by the neurotransmitters, but they are not ion channels. I
What happens when glutamate is released?
In excitatory synapses, besides AMPA and NMDA receptors, there is another type of receptors which is mGluR’s receptors (Metabotropic glutamate receptors). When glutamate is released, it binds to metabotropic receptors, the receptors change their shapes, leading to a series of reactions inside the postsynaptic cell.
