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Neurotransmitters (Chapter 6)
Terms in this set (62)
What are the 2 categories of neurotransmitters?
small molecule neurotransmitters & peptide neurotransmitters
____________________: individual amino acids or other small molecules
_____________________: relatively large molecules—3 to 36 amino acids in length
What is the 1st identified neurotransmitter - and the most studied since
_______________________: Neurotransmitter used at neuromuscular junction of skeletal muscle, vagus/cardiac synapse, ganglia of visceral motor system
-less understood role in CNS
After ACh vesicular release, what occurs?
What type of receptor is the Nicotinic ACh receptors (nAChR)?
___________ ____________:nonselective to cations; passes both K+ & Na+ and produces EPSPs
The Nicotinic ACh receptors (nAChR) are named after exogenous chemical __________, which binds & activates nAChRs (agonist)
Feelings of __________, _________& ___________ with nicotine mediated by nAChRs in the CNS
The snake venom α-bungarotoxin binds & _________ nAChRs (antagonist)
nAChR is comprised of ___ subunits, 2 of which (__ subunits) must bind ACh in order to _________
-ensures that channel opens only with high concentration of ACh in the synaptic cleft
Different combinations of 5 subunits make different subtypes of nAChRs, each with different __________ responses
Like nAChR, all ionotropic receptors are comprised of __ or __ subunits
-diversity of receptor subtypes
4 or 5
The Muscarinic ACh receptor (mAChR) is what type of receptor?
Muscarinic ACh receptor (mAChR) mediates most effects of ACh in the _________.
Does the Muscarinic ACh receptor (mAChR) have subunits?
-how many membran-spanning regions does it have?
No subunits - single protein complex with 7 membrane-spanning regions
Binding of ACh causes ___________ change, which allows binding of ___ _________
____ subtypes of mAChRs—each activates a different G-protein
-> variety of postsynaptic effects
-All ultimately affect ____ ____________ - some inhibitory and some excitatory
Like mAChR, all metabotropic receptors have __________ subtypes
Review of G-protein-coupled receptors: What is a typical signal cascade?
-Activation of metabotropic receptor may cause opening or closing of postsynaptic ion channels at any of these points
Typical signal cascade: G-protein-coupled receptor --> G protein --> Effector protein --> 2nd messenger --> Protein kinase or phosphatase --> Increase or decrease in protein phosphorylation
Review Protein synthesis triggered by protein kinases:
Example: CREB (cAMP response element binding protein)
-CREB bound to cAMP response element (CRE) site of DNA
-PKA, CAMKII or MAPK (protein kinases) phosphorylate CREB
-Activated CREB increases transcription at the CRE site
-Genes downstream of CRE site transcripted, then translated into new proteins
Synaptic signal --> CREB activation --? Protein synthesis
Over half of all neurons (and nearly all excitatory neurons) transmit __________
After glutamate vesicular release --> ____________
What are the 3 ionotropic Glutamte (Glu) receptors:
AMPA, NMDA & Kainate
The 3 ionotropic Glu receptors: AMPA, NMDA & Kainate are named for the _________ drugs that selectively activate them.
The 3 ionotripic Glu receptors all create __________; channels pass both ___ and ___.
EPSPs; Na+ and K+
Most synapses express both AMPA & NMDA; _________ less prevalent
_______________:: larger amplitude, faster onset, faster decay
________________:smaller amplitude, slower onset, slower decay
______________: smaller amplitude, faster onset, slower decay
Unique properties of the NMDA receptor:
1. Requires _________ as a co-agonist to activate.
2. Has a wider pore that allows ____, in addition to Na+ and K+.
-the increase in [Ca2+]in acts as a 2nd messenger in an intracellular signaling cascade
3. Is blocked by _____ at hyperpolarized potentials; only opens with a strong depolarization, such as an action potential
Also, ____ subtypes of metabotropic Glu receptors exist—all very slow responses compared to the ionotropic receptors
GABA & glycine are the neurotransmitters expressed at most __________ synapses
1/3 of brain synapses contain ______; mostly local interneurons, not projection neurons
Two types of ionotropic GABA receptors: ___________ & __________.
GABAA & GABAC
Two types of ionotropic GABA receptors: GABAA & GABAC:
-Both are _________ channels; mostly pass _____, which is highly concentrated outside the neuron
-Erev for Cl− is usually ________ spike threshold --> either hyperpolarizing or shunting inhibition
Drugs that are agonists for ionotropic GABA receptors:
-____________, used to reduce anxiety (ex: Valium)
-____________, used for anesthesia/epilepsy (ex: pentobarbital)
-____________, used for pleasure!
Ionotropic Glycine receptors also mostly pass ________
-Potently blocked by plant poison, strychnine
Most effects of biogenic amines are mediated by ____________ receptors
Dopamine has a major presence in ____________ ___________ projecting onto striatum
-These neurons degenerate in ___________ disease.
____________ plays essential role in coordination of movement; also has a role in motivation, reward & reinforcement (biogenic amine)
Cocaine and amphetamines _________ the presynaptic reuptake transporter of dopamine
--> dopamine remains in the synaptic cleft longer
_________________:Role in sleep & wakefulness, attention & feeding behavior (biogenic amine)
Norepinephrine (Noradrenalin) is present in __________ ___________ with widespread projections to forebrain
_______________: Found in fewer neurons of the brain - role not well-defined (biogenic amine)
________________:Found in neurons of the hypothalamus with widespread projections to nearly all brain & spinal cord areas (biogenic amine)
-Role in arousal & attention
________________:Largely found in Raphe nucleus of pons, with widespread projections to forebrain (biogenic amine)
-Role in sleep & wakefulness
- Impairments in ____________ metabotropic receptors are implicated in many psychiatric disorders (depression, anxiety, schizophrenia) and eating disorders (function in mediating satiety)
Selective Serotonin Reuptake Inhibitors (SSRIs, like Prozac) block the _____________ transporters that remove serotonin from the synaptic cleft
-->serotonin remains in synaptic cleft longer
ATP not only provides energy, but can also act as a __________________
- ATP is contained in all ____________ ______________ and co-released with traditional neurotransmitters
ATP is degraded in the _________ ________ into adenosine—postsynaptic receptors exist for both ATP & adenosine
____________ blocks the adenosine receptor—thought to mediate its stimulant effect
-Neuropeptides are made from originally _________ peptides in the cell body
-Larger peptides are loaded into _________, then sent down axon (____ axonal transport)
-Cleavage of larger peptide into neuropeptides takes place in ___________
-One vesicle can contain different neuropeptides
Peptide metabotropic receptors are activated by small amounts of _____________
--> neuropeptide release at one site can have effect at distant site
What are the 5 loose groups of neuropeptides?
brain/gut peptides, opioid peptides, pituitary peptides, hypothalamic releasing hormones, and "others"
______________: Named after the chemical opium, which activates the same receptors
-Other agonists are morphine & fentanyl (80 times more potent than morphine)—potent analgesics; also highly prone to tolerance
Endogenous opioid peptides are enkephalins, endorphins & dynorphins
-tend to be synaptic ___________
-Role in sexual attraction, submissive/aggressive behavior
Unconventional neurotransmitters are chemicals produced in one neuron that have an effect in another, but aren't released by synaptic ___________
-An example: Endocannabinoid receptor activation inhibits the amount of GABA released by inhibitory interneuron
___________: often participate in retrograde signaling
What are the 3 steps in retrograde signaling?
1. Depolarization in postsynaptic neurons increases [Ca2+]in
2. [Ca2+]in increase triggers endocannabinoid synthesis & release
3. Endocannabinoids diffuse through cell membrane & activate cannabinoid receptors on the presynaptic terminal
_________: is a gas that can be produced in neurons and diffuse several micrometers before being degraded
-can pass into another neuron and act as a 2nd messenger in an intracellular signaling cascade
Nitric oxide (NO)
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