NEUROSCI 101 Lecture Notes - Lecture 4: Neurotransmitter Receptor, Neuromuscular Junction, Signal Generator

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17 May 2016
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Ch. 13 Neural Basis of Memory
Pre Lecture Questions:
Each neuron synthesizes and releases only one neurotransmitter
F, neurons can release multiple types of NTs
Dopamine can trigger either an IPSP/EPSP depending on what receptor its binding to
T for multiple neurotransmitters
If you blocked Ca2+ at the end of the axon, more neurotransmitters would be released
F, need Ca uptake for vesicles to release NTs into the synapse since the
depolarization of the neuron cell will open the Ca2+ gates and stimulate the
release of NTs from vesicles
Glutamate is the neurotransmitter used in the peripheral nervous system at every
neuromuscular junction.
F, acetylcholine (ACh)
If I discovered a drug that rapidly stimulated an EPSP in a postsynaptic cell, what type of
receptor is it likely bound to?
ionotropic receptor, which leads to direct opening of ion channels but is shorter
acting, explaining the rapid stimulation
Three Steps in Stimulating a LTP:
record the EPSP with a recording electrode to record the baseline
give a pulse burst, a high frequency stimulation with an electrode
give the same pulse at the time of the pre-tetanus
What NTs/receptors are involved in LTP?
NT: Glutamate
Receptors: AMPA, NMDA
● AMPA
excitatory ionotropic postsynaptic receptor
Glutamate binds to the receptor, Na+ flows in, depolarizes the cell
strictly chemically gated, glutamate binds to receptor, Na+ influx causes EPSP
● NMDA
Mg2+ ion sits in the channel, blocking the channel opening from Ca2+ to come in
thus, postsynaptic dendrite is NOT depolarized
depolarization of postsynaptic cell leads to Mg coming off, Ca coming in when
receptors bind to AMPA in other areas
Glutamate binds to the receptor, Ca2+ flows in, depolarizes the cell
chemically and voltage gated
after depolarization of the postsynaptic membrane via AMPA receptor
activation, Mg is removed and NMDA allow Ca to enter in response to Glu
When depolarization occurs after AMPA/NMDA stimulation, more AMPA receptors are
activated. Release of retrograde signal generator, which enhances more Glu release
and thus more vesicles to release their contents simultaneously.
After tetanus, same axn pot will produce a larger postsynaptic polarization
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Multiple tetnuses over time to enhance learning: genetic alteration > therefore Increased
protein synthesis leads to building more synapses
post - no of receptors
pre - no of NTs
long term - changes in protein synthesizers that alter gene structure and synaptic
connections
consistent w/ Hebb’s Law
Is LTP the mechanism of learning and memory formation?
consistent w/ conditions necessary for memory
correlational observations - time course of LTP similar for memory formation
somatic interventions - pharmacological treatments that block LTP impair learning
behavioral interventions - training an animal in a memory task can induce LTP
Does hippocampus have special role in spatial navigation?
behavioral studies show that lesions to the hippocampus disrupt navigation that is
directed by relational cues, but not stimulus response learning
hippocampus has “place cells” that fire only when the animal is in the same location as
determined by the relational cues
explains why rats that go back to the same location in memory will retrieve
memories that happened in that location
hippocampus required for relational learning, but not stimulus-response learning
ex. rats swimming in a pool to find hidden platform (hippocampal learning with
regards to spatial recognition)
relational learning - start animal in different location on each trial, requires
multiple cues to know where you are in space
control rat gets better, hippocampal lesioned rat constant time
stimulus-response learning - start animal in same location on each trial
both control and lesioned rats learn just as quickly
DON’T NEED HIPPOCAMPUS TO DO STIMULUS RESPONSE
LEARNING
hippocampal place cells only fire when the animal is in a particular spatial location
defined by relational cues in the environment
but if we move the cues around in the environment, locations in which place cells
would fire change
John O’Keefe, May-Brit and Edvard Moser won Nobel Prize in 2014 for discovering
place cells in the hippocampus
Systems Neuroscience of Memory
1. HM, lasting legacy
2. taxonomy of memory
3. hippocampus (medial temporal lobe) not important to all types of memory
4. memory is transferred from hippocampus to neocortex for storage
Cognitive Neuroscience/Psych Definitions:
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