Term
| What are the criteria for a putative neurotransmitter? |
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Definition
The substance is synthesized in the neuron.
It is present in the presynaptic terminal and is released in amounts sufficient to exert its supposed action on the postsynaptic neuron or effector organ.
When applied exogenously, it mimics exactly the action of the endogenously released transmitter.
A specific mechanism exists for removing it from its site of action (e.g., synaptic cleft). |
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Term
| What are the two classifications of transmitters? |
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Definition
Small-Molecule, Rapidly Acting Transmitters
Cause most of acute responses of nervous system
Example – transmission of sensory signals to brain and motor signals back to the muscles. acetycholine
Large-Molecule, Slowly Acting Transmitters
Cause more prolonged actions
Example – long-term changes in numbers of receptors, long-term opening or closure of certain ion channels, neuropeptides |
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Term
| What are the basics of acetylcholine? |
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Definition
Acetylcholine (ACh) is a "classical" NT
Large pyramidal cells of the motor cortex, neurons in the basal ganglia, and motor neurons innervating skeletal muscle use it
Has inhibitory effect on cardiac muscle (vagus nerve)
Transmitter in all preganglionic neurons and postganglionic neurons of parasympathetic nervous system
Transmitter in all preganglionic neurons of sympathetic neurons.
ACh receptors are termed "cholinergic" |
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Term
| What are some important amine neurotransmitters? |
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Definition
They are termed biogenic Amines or catecholamines
Epinephrine (EPI, Adrenaline) - use adrenergic receptors
Norepinephrine (NE, Noradrenaline) - use noradrenergic receptors
Dysfunction can cause bipolar disorder & schizoprenia, regulation of mood, responsible for some symptoms of depression
Dopamine
Serotonin (5-HT) |
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Term
| What are the basics of epinephrine? |
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Definition
it is an amine neurotransmitter
EPI in chromaffin cells of adrenal medulla
In CNS EPI believed to play a role in regulation of BP
In periphery, EPI is the main circulating excitatory transmitter released during the “fight or flight” stress reactions |
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Term
| What are the basics of norepinephrine? |
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Definition
amine neurotransmitter
In CNS NE in Locus Coreleus – inhibitory effect
In CNS – NE involved in alertness and wakefulness
NE is the primary transmitter for postganglionic sympathetic neurons with an excitatory influence.
NE is released by internal organs, including gut, spleen, and heart. |
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Term
| What are the basics of dopamine? |
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Definition
amine neurotransmitter
Dopaminergic neurons prominent in certain midbrain regions
Dysfunction – Degeneration of dopaminergic neurons in basal ganglia of substantia nigra occurs in Parkinson’s Disease |
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Term
| What are the basics of serotonin? |
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Definition
amine neurotransmitter
5-Hydroxytryrptamine (5-HT)
Found throughout brain, primarily synthesized in the brain stem.
Mostly inhibitory effects on postsynaptic membrane.
Involved in control of eating, sleep and arousal.
Dysfunction – implicated in bipolar disorder, depression. |
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Term
| How does acetycholine re-uptake work? |
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Definition
ACh is degraded into choline and acetyl CoA by the enzyme acetylcholinesterase.
The Na+-choline uptake cotransporter (secondary active transport) is how choline gets back into the presynaptic terminal |
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Term
| How are epinephrine, norepinephrine, and dopamine related? |
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Definition
| They are all biogenic amines which share tyrosine as a common precursor in their biosynthesis. |
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Term
| How does reuptake work for norepinephrine? |
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Definition
one method of uptake is the Na+-Cl-NE cotransporter
another method is facilitated diffusion |
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Term
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Definition
| An antidepressant that blocks re-uptake of dopamine and norepinephrine |
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Term
| What is the clinical use of L-Dopa? |
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Definition
It is used in Parkinson's
In Parkinson's there is degeneration of dopaminergic neurons in the brain
Dopamine can't cross the blood brain barrier but L-Dopa (its precursor) can |
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Term
| What is the role of glutamate in neurons? |
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Definition
It is an amino acid NT
Principle excitatory transmitter in the brain
Plays a role in learning and memory |
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Term
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Definition
Gamma amino butyric acid has widespread distribution throughout brain and spinal cord.
Potent inhibitory transmitter necessary for stabilizing electrical activity
GABA alpha receptor – ligand-gated Cl channel – increases Cl influx to produce IPSPs (hyperpolarizing)
Benzodiazepines (e.g., librium) – anticonvulsants and sedatives. Facilitates action of GABA at GABA aplha (Barbiturates & alcohol)
GABA beta receptor activation increases K conductance via activation of a G protein to produce IPSPs (hyperpolarizing)
GABA plays a role in learning and memory |
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Term
| What is the importance of glycine in neurons? |
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Definition
It is an amino acid NT
Important inhibitory neurotransmitter in the spinal cord and lower brainstem
Not well-studied but when glycine receptors are blocked, you experience continuous contraction would occur (lock-jaw) |
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Term
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Definition
Most peptides serve as neuromodulators, but some act as neurotransmitters.
Synthesized in the neuronal cell body, packaged in secretory vesicles and transported to the tips of nerve fibers by axonal streaming of axon cytoplasm
Smaller amounts of neuropeptides are released compared to “classical’ transmitters but much more potent causing more prolonged actions.
Examples of actions – prolonged changes in metabolic machinery of cells, prolonged changes in activation or deactivation of specific genes in cell nucleus, prolonged alterations in number of excitatory or inhibitory receptors. |
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Term
| What are important properties of neuropeptides? |
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Definition
synthesized as a large precursor protein at the soma and transported to release sites; must be replenished by synthesis at soma
slow postsynaptic effects
actions terminated by extracellular proteases or by diffusion
co-released with "classical" NT's
can trigger complex coordinated behaviors
actions do not require point-to-point synaptic connections |
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Term
| What are properties of the nonpeptide transmitters? |
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Definition
synthesized and packaged in nerve terminal
synthesized in active form
present in small, clear vesicles
released into a synaptic cleft
action terminated by uptake by presynaptic terminal by Na+-powered active transport
action typically has short latency and short duration |
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