M1 Lec 6 Flashcards
whats an essential step of the AP for the release of NT?
the Ca2+ influx
what are EPSPs (Excitatory Postsynaptic Potentials) + ex:
depolarizations caused by the influx of positive ions (e.g., Na⁺) that increase the likelihood of a neuron reaching the threshold to fire an action potential
* glutamate or Ach
what are IPSPs (Inhibitory Postsynaptic Potentials) + ex:
hyperpolarizations caused by the influx of negative ions (e.g., Cl⁻) or efflux of positive ions (e.g., K⁺), decreasing the likelihood of an action potential.
* ex: GABA or glycine
what did donald hebb come up with?
synaptic plasticity
* refers to the ability of synapses to strengthen or weaken over time in response to activity, experience, or changes in signaling
* it is a key mechanism underlying learning, memory, and neural adaptation.
what is habituation
organism decreases its response to a repeated, harmless (innocuos) stimulus over time, as it learns the stimulus is not significant or threatening.
- decrease in gill withdrawal for slug
what is sensitization
n organism’s response to a stimulus becomes stronger over time, often due to the stimulus being intense, noxious, or paired with an aversive event
- enhanced gill withdrawal after noxious stimulus for slug
results of phosphorylation (adding phosphorus to molecule)
- Reduces channel opening
- Prolonged action potential
what does long term sensitizaion result in
- Persistently active protein kinase A.
- This sustained activity can lead to long-term changes in cellular function, including gene expression, metabolism, or synaptic plasticity.
what is Long-term potentiation (LTP)
enhancement in synaptic strength that occurs after repeated stimulation of a synapse and it is considered a cellular mechanism for learning and memory. This makes the synapse more efficient, resulting in larger EPSPs for the same stimulus in the future.
- induced after tetanus
- pathway specific
Tri-synaptic circuit:
refers to a pathway in the hippocampus involved in memory processing, consisting of three key synapses
- Perforant path: Cortex to granule cells
- Mossy fibers: Granule to CA3
- Schaffer collateral pathway: CA3 to CA1
hebbian plasticity
* ltp in which neurons is hebbian
a form of synaptic plasticity where the synapse between two neurons strengthens if they are activated simultaneously. “cells that fire together, wire together.”
* * LTP in CA1 pyramidal neurons is Hebbian
what are the 2 traits of hebbian plasticity?
- Specificity: Only the synapses that are active at the same time as the postsynaptic neuron will strengthen.
- Associativity: If a weak synapse and a strong synapse synapse onto the same postsynaptic neuron and are activated simultaneously, the weak synapse can also be strengthened, making it more effective in the future.
What happens if a subthreshold stimulus is applied to a CA3 neuron while a depolarization current is simultaneosly applied to CA1 neuron?
The simultaneous activity of the presynaptic (CA3) and postsynaptic (CA1) neurons results in an increased excitatory postsynaptic potential (EPSP), showing that the synapse has been strengthened (LTP).
This causes the the postsynaptic receptors to detect coincidence of presynaptic and postsynaptic activity.
what is coincidence detection?
both pre and post-synaptic neurons active
what are
Ionotropic glutamate receptors
a type of receptor that binds glutamate (the primary excitatory neurotransmitter in the brain) and directly mediates the flow of ions across the cell membrane.
They are ligand-gated ion channels, meaning that when glutamate binds to them, they open and allow specific ions to pass through.
what are the two types of ionotropic glutamate receptors?
AMPA/Kainate: when bound it allows for passage of Na+ and K+ ions. Its fast/excitatory. AMPA receptors are activated by glutamate and contribute to postsynaptic depolarization (crucial to activate NMDA)
NMDA: when bound allows for Na+, K+, Ca2+ ions to pass.
* also serve as coincidence detectors in LTP by detecting pre and post synaptic activity.
NMDA receptors have 2 requirements in order to act as coincidence detectors. What are the 2 reqs? What happens when theyre met?
- Glutamate releases from the presynaptic neuron (CA3) to bind to the receptor and activates it
- NMDA receptors are blocked by Mg2+ during rest. They need postsynaptic depolarization to remove this block on the receptor channel
- When both conditions are met, calcium (Ca²⁺) enters the postsynaptic cell, triggering molecular cascades that strengthen the synapse (LTP).
What is LTD (Long-term synaptic
depression)
LTD refers to a long-lasting decrease in synaptic strength, which can play a role in synaptic plasticity, learning, and memory, just like LTP but in the opposite direction.
What are the Schaffer collaterals?
The Schaffer collaterals are the axons of the pyramidal neurons in the hippocampus that synapse on other pyramidal neurons, specifically in the CA1 region.
What does induction of long-term synaptic depression (LTD) in the Schaffer collaterals involve?
* whats the process
* discuss calcium
* discuss AMPA
- It involves a process by which synaptic strength between neurons is enhanced following low-frequency stimulation (1 Hz). This low-frequency stimulation causes a weaker, more prolonged depolarization of the postsynaptic neuron.
- calcium rise is small/slow. The gradual, less intense calcium signaling leads to different intracellular signaling pathways that promote synaptic weakening.
- One of the key mechanisms of LTD is the internalization (removal) of AMPA receptors from the postsynaptic membrane. Fewer AMPA receptors on the postsynaptic side reduce the neuron’s sensitivity to glutamate, weakening the synapse.
