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brau2308
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Transmitter Substances:
term which implies they are involved w/ transmission of AP from one neuron to the next or to a mm cell or gland
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Neurotransmitters are released from:
pre-synaptic neuron
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The neurotransmitter affects:
the postsynaptic membrane (neuron, MM cell, gland cell) in a specific manner in milliseconds
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Are neurotransmitters excitatory or inhibitory?
- may be either
- some NT may have opposite effects on different types of neurons
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What determines if a neurotransmitter is excitatory or inhibitory?
based on chemical nature of receptor
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Can the same neuron have receptors for many types of NT?
yes
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Can NT respond to different inputs?
yes
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What are different receptors called?
receptor subtypes
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What is the criteria of a NT?
- must be synthesized in the neuron and localized in the presynaptic membrane
- must be released into the synaptic cleft
- needs to bind to receptors of the postsynaptic membrane
- needs to be removed from receptor by specific mechanisms
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Are the receptors of the postsynaptic membrane ligand or voltage gated channels?
ligand
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What do the receptors of the postsynaptic membrane do?
control conductance of ions (hyper or hypopolarized)
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What are the common neurotransmitter?
- ACh
- dopamine
- serotonin
- GABA
- Glutamate
- Glycine
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Is ACh excitatory or inhibitory?
majority of the time excitatory but can be inhibitory
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Where is ACh found?
- neuromuscular junction
- all pre and post ganglionic parasympathetic neurons
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What is ACh associated w/?
preganglionic sympathetic neurons
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Is dopamine excitatory or inhibitory?
inhibitory in nature
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Where is dopamine produced?
substantia nigra
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Where does dopamine end up?
in basal ganglia
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What does dopamine do?
control muscle activity
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What disease is dopamine associated with?
Parkinson's disease
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What is Parkinson's disease?
overactivity of dopamine (involuntary muscle contractions)
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What part of the nervous system is serotonin involved w/?
CNS
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Is serotonin excitatory or inhibitory?
either
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What does serotonin impact?
emotion (depression, limbic, feelings)
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What does GABA stand for?
gamma amino butyric acid
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Is GABA excitatory or inhibitory?
major inhibitory NT in NS
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Does GABA have lots of subtypes?
yes
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What does GABA cause?
inhibitory post-synaptic potentials
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What does GABA bind to?
ligand gated channels to allow Cl in
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What is glutamate?
an amino acid
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Is glutamate excitatory or inhibitory?
major excitatory NT in NS
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Glutamate is the cousin of?
GABA
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What is glycine?
an amino acid
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Is glycine excitatory or inhibitory?
usually inhibitory in spinal cord
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Neuromodulators are chemicals that interact w/ pre and post synaptic membranes and are usually linked to:
G-protein and Second messenger systems
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Are neuromodulators considered a fast or slow system when compared to NT?
slow (may take seconds, hours, or days to manifest)
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Neuromodulators modulate rather than:
initiate activity
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What is the function of neuromodulators?
- initial binding w/ receptor proteins (pre and post synaptic membrane)
- receptor contacts and activates molecules call G-proteins which are located inner layer of cell membrane
- G-proteins become involved w/ cAMP (cyclic adenosine monophosphate) which is called a second messenger molecule
- second messenger molecules set into action very complicated cascades of metabolic activity utilizing kinases and phosphorylation activity, influencing nature of the recptors
- increased activity results in changes in the biochemical nature of the neuron
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What are the changes in the biochemical nature of the neuron form increased activity?
- produces changes in the molecular nature of the protein receptor modules resulting in opening or closing the channels, changing the sensitivity
- Alterations of gene expression (up or down regulation of genes)
- alteration of protein synthesis
- long term effects associated w/ memory and learning
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What are some common neuromodulator molecules?
- dopamine
- norepinephrine/epinephrine
- serotonin
- neuroactive peptides
- adenosinenitric oxide
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Although common neuromodulator molecules are found in all cells of the body, we are focusing on:
their context related to neurons
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What are neuroactive peptides?
small protein molcules
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What are some neuroactive peptides?
- substance P (pain processing)
- Endorphins (endogenous opiods)
- VIP (vasoactive intestinal polypeptides)
- about 40 others have been ID
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What are the characteristics of receptors?
- determine sif a substance that binds to it will behave as NT or NM
- Receptor is always facing outward (w/ few exceptions) so they can interact w/ ligands
- protein molecules
- found on outer surface of cell membrane
- 2 Parts: binding component and ionophore component
- have multiple subunits
- ligand-gated channels
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ACh to a nicotinic receptor on NMJ acts a a NT or NM
NT
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Ach to muscarinic receptor acts as NT or NM?
NM
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Binding component of a receptor:
active site, specific for different transmitter substances (TS)
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Ionophore component
pore component (protein pore through which the ions will flow)
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Ionotrophic receptors:
bonding to NT; receptors which receive neurotransmitters
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Metabotrophic receptors:
binding to NM; receptors which receives neuromodulators
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What are the properties of amino acid ligand gated channels?
- pharmacology of the binding sites
- kinetics
- selectivity
- conductance
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What is the pharmacology of the binding sites of amino acid ligand gated channels?
- channels, pores, receptors
- which neurotransmitters influence the receptors as well as drugs
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What are the kinetics of amino acid ligand gated channels?
binding process and channel gating and ultimately the duration of the effect (gating process- rate of interaction)
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What is the selectivity of amino acid ligand gated channels?
- which ions will flow through receptor?
- IPSP or EPSP?
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What is the conductance of amino acid ligand gated channels?
- magnitude of the effect
- quantity of ions passing through
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