PSYC1011 Lecture Notes - Lecture 5: Slow-Wave Sleep, Basal Forebrain, Substantia Nigra
The basics of neurochemistry
• Types of neurotransmitters and receptors
• Major functions of some neurotransmitters
• Clinical relevance of some neurotransmitter systems
•
Neurotransmitters
• Criteria
o Substance must be present within the presynaptic neuron
o Substance must be released in response to presynaptic depolarisation
▪ Release must be Ca2+ dependent
o Specific receptors for the substance must be present on the postsynaptic cell
Neuromodulator
• Neuromodulation occurs when a neurotransmitter is released and is not returned to the
presynaptic cell
o Does not specifically work on the synapse
• Neurotransmitter travels to modulate the activity of other cells
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•
• Many neurotransmitters act as neuromodulators
o The monoamines
o Cholinergic system
o Neuropeptides
Types of receptors
• Ionotropic
o Neurotransmitter binds to a receptor complex that directly opens ion channels
o Ligand-gated ion channels
• "ligand" = neurotransmitter
▪ Neurotransmitter binds
▪ Ion channel opens
• Specific to ion
▪ Rapid effect
▪ Generates EPSPs and IPSPs
• To increase or decrease excitation of the cell
▪
• Metabotropic
o G-protein coupled receptors
o Indirectly opens ion channels
o Neurotransmitter binds at receptor
▪ G-protein is released, acting as a intracellular messenger that activated the ion
channel
o Many hundreds of GPCRs in the brain
▪ A large number have no identified function
o In the most basic form of GPCR
▪ Neurotransmitter binds
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▪ Activates a "G-protein"
▪ G-protein may open an ion channel
▪
o G-protein
▪ Are intracellular messengers
• Could activate an enzyme cascade
• This could change the way the cell works
• Altering gene expression
o
• Intracellular messengers
• Slow/long acting
Neurotransmitter types
• Amino acid neurotransmitters
o Glutamate
▪ Primary excitatory neurotransmitter
• More likely to make other cells fire
o Gamma-aminobutyric acid (GABA)
▪ Primary inhibitory neurotransmitter
• Inhibits other cell from firing
o Glutamate
▪ Estimated that ~50% of synapses utilise glutamate
▪ Three ionotropic receptor types:
• AMPA - Initiating EPSPs
• Kainate - initiating EPSPs
• NMDA - neuroplasticity and learning
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