Plasticity Flashcards
What is plasticity?
The ability of the brain to chaneg
How are connections fine-tuned?
As we interact with our environment, synaptic connections start to change, with new ones being made, useful connections becoming stronger and connections that are infrequently used becoming weaker or even lost for good
What is a normal electrical response to neurotransmitter release a measure of?
Synaptic strength
What process has long-lasting enhancement in synaptic strength that can be produced by brief periods of neuronal activity?
Long-term potentiation (LTP)
Which process has long-lasting depression in synaptic strength that can be produced by brief periods of neuronal activity?
Long-term depression (LTD)
What is a common amino acid used to build proteins?
Glutamate
Where do glutamate function?
Most plastic synapses, those that exhibit LTP and LTD
Where are Glutamate receptors found?
At the receiving side of the synapse
What are the 4 variates of Glutamate receptors?
Ionotropic receptors: AMPA, NMDA and kainate
Metabotropic receptors: mGluR
Do all types of glutamate receptors respond to the same type of neurotransmitter?
Yes
What are the functions of ionotropic glutamate receptors?
They use their ion channels to generate an excitatory post-synaptic potential (epsp)
What is the function of metabotropic glutamate receptors?
Modulate the size and nature of the response
What receptors are most commonly thought of as memory molecules?
AMPA and NMDA
What receptors are the fastest to act?
AMPA receptord
What happens when glutamate is bound to AMPA receptors?
The receptors rapidly open their ion channels to produce a transient (not permanent) excitatory postsynaptic potential, the glutamate is only bound to the AMPA receptor for a fraction of a second and once it leaves and it removed from the synapse, ion channels close and electrical potential reverts to its resting state
What is the critical molecule that trigger synaptic plasticity?
NMDA receptors
How does glutamate bind to NMDA receptor?
It binds to NMDA receptors on the postsynaptic neuron
What happens to the NMDA receptor when the synapse is activated slowly?
The NMDA receptors play little to no role
Why do NMDA receptors play little to no role when NMDA receptors are activated slowly?
As soon as NMDA receptors open their ion channels, it becomes plugged by Mg2+ ions that are present in the synapse
What happens when synapse are activated by several pulses very quickly to a set of inputs on to a neuron?
The greater synaptic activity causes a large depolarisation in the postsynaptic neuron and this dispels Mg2+ from the NMDA ion channels by a process of electrical repulsion, NMDA receptors can then partake in synaptic communication
What are the ways NMDA receptors undergo synaptic communication?
- They conduct Na+ and K+, which adds to the depolarisation
- They allow Ca2+ to enter the neuron
What happens when Ca2+ enters the neuron?
Ca2+ binds to proteins located extremely close to the synapses where the NMDA receptors were activated, many of these proteins are physically connected to the NMDA receptors in a molecular machine, some are enzymes that are activated by Ca2+ which leads to chemical modifications of other proteins within or close to the synapse, these chemical modifications are the first stages of formation of the memories
What are the ways to express change in strength?
- Enable AMPA receptors to work more efficiently, such as pass more current into the neuron upon activation
- Enable more AMPA receptors to be inserted into the synapse
How does the two ways lead to change in strength?
They both lead to a larger epsp, LTD
What does the reduction in efficiency and number of AMPA receptors result in?
LTD
What is the beauty of the mechanism of inducing LTP or LTD?
It’s relative simplicity that all can occur within a single dendritic spine and therefore alter synaptic strength in a highly localised manner
What are the structural alterations that occur in the brain when memories become more permanent?
Synapses with more AMPA receptors inserted following the induction of LTP change their shape and may grow bigger or new synapses may sprout out of the dendrite so the job of one synapse can be done by two
What happens to synapses that lose AMPA receptors following the induction of LTD?
They may wither and die
What is how well we learn influenced by?
Our emotional state and when we pay attention
What neuromodulator is released during heightened attention?
Acetylcholine
What neuromodulator is released during novelty, stress and anxiety?
Cortisol
What other neuromodulators are released during emotional states?
Dopamine, noradrenaline and steroid hormones
What do modulators do to neurons?
They change the functioning of NMDA receptors, activate special genes specifically associated with learning, make proteins to stabilise LTP and make it last longer
What happens when neurons are damaged?
Neurons do not grow back but other neurons adapt and can take on similar functioning roles to lost neurons, forming another network that is similar
