PSYB65H3 Lecture Notes - Lecture 4: Neurotransmitter Receptor, Acetyl-Coa, Axon Terminal

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18 Nov 2012
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Lecture 4
Neurotransmitters
- when action potential goes past the threshold, Na channels open and lots
of sodium enters the neuron and neuron fires
Action potential: large positive charge across the neural membrane, caused
by sodium influx
- info travels down the axon until the synaptic terminal button – which
meets w a dendrite of the next neuron
- presynaptic => axon
- postsynaptic => dendrite
- junction = synapse; space in between is the synaptic cleft
- synaptic vesicles get released from presynaptic axon when action potential
hits – fuse w the membrane and empty transmitter substance contents into
synaptic cleft
- transmitter interacts w receptors on the postsynaptic membrane of
dendrite => cause channels to open, allow Na to enter and continues the
action potential
- in order to transmit information transmitter needs to interact, but needs to be quickly inactivated so that a different signal
can come in
- chemicals in the synaptic cleft exist to breakdown transmitters
Life cycle of transmitter:
1. synthesis – from basic ingredients
2. storage – critical bc can be broken down by enzymes if not stored properly
3. vesicle release – usually when there’s an action potential
4. interaction w receptor – transmission to the next cell
5. inactivation – reuptake or degradation/breakdown
2 ways to alter a system – can increase or decrease functional activity
=> can do this in each step of the life cycle
Increase functional activity Decrease functional activity
1. Synthesis Production of more transmitter
increases functional activity
- eg in parkinson’s disease give
more L-dopa to increase synthesis
of dopamine
Reduction of transmitter
production
- eg in sch decrease dopamine
2. Packaging
- - -
- decrease packaging allows
transmitter to get destroyed
=> very little left for release
3. Release - more release leads to more
neuron firing
- decrease release
4. Receptor activation - administer mimicker - administer blocker
5. Inactivation - decrease breakdown
=> keeps stimulation on
postsynaptic receptor longer
- increase breakdown, before the
transmitter can reach the receptor
Mimicker: chemicals that can mimic the activity of a neurotransmitter; very similar to the transmitter in molecular shape
=> activates the receptor of the transmitter
Blocker: fits perfectly in the receptor site, but no activation – blocks channel from opening
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