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15 Cards in this Set

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neurotransmitters
are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell.
nt groups
1) amino acids (primarily glutamic acid, GABA, aspartic acid & glycine), (2) peptides (vasopressin, somatostatin, neurotensin, etc.) and (3) monoamines (norepinephrine NA, dopamine DA & serotonin 5-HT) plus acetylcholine (ACh).
major "workhorse" neurotransmitters of the brain
glutamic acid (=glutamate) and GABA
small molecule nt
acetylcholine, 5 amines, and 3 or 4 amino acids (depending on exact definition used), Purines, (Adenosine, ATP, GTP and their derivatives) are neurotransmitters.
receptor
dictates the neurotransmitter's effect
nt axn
Acetylcholine - voluntary movement of the muscles
Norepinephrine - wakefulness or arousal
Dopamine - voluntary movement and emotional arousal
Serotonin - sleep and temperature regulation
GABA (gamma aminobutryic acid) - motor behaviour
Glycine - spinal reflexes and motor behaviour
Neuromodulators - sensory transmission-especially pain
moa nt
Within the cells, small-molecule neurotransmitter molecules are usually packaged in vesicles. When an action potential travels to the synapse, the rapid depolarization causes calcium ion channels to open. Calcium then stimulates the transport of vesicles to the synaptic membrane; the vesicle and cell membrane fuse, leading to the release of the packaged neurotransmitter, a mechanism called exocytosis.

The neurotransmitters then diffuse across the synaptic cleft to bind to receptors. The receptors are broadly classified into ionotropic and metabotropic receptors. Ionotropic receptors are ligand-gated ion channels that open or close through neurotransmitter binding. Metabotropic receptors, which can have a diverse range of effects on a cell, transduct the signal by secondary messenger systems, or G-proteins.

Neuroactive peptides are made in the neuron's soma and are transported through the axon to the synapse. They are usually packaged into dense-core vesicles and are released through a similar, but metabolically distinct, form of exocytosis used for small-molecule synaptic vesicles.
glutamate
ost prominent of excitatory transmitters
gaba and glycine
inhibitory neurotransmitters
reuptake
Many neurotransmitters are removed from the synaptic cleft by a process called reuptake (or often simply uptake). Without reuptake, the molecules might continue to stimulate or inhibit the firing of the postsynaptic neuron. Another mechanism for removal of a neurotransmitter is digestion by an enzyme. For example, at cholinergic synapses (where acetylcholine is the neurotransmitter), the enzyme acetylcholinesterase breaks down the acetylcholine. Neuroactive peptides are often removed from the cleft by diffusion, and eventually broken down by proteases.
serotonin
released specifically by cells in the brainstem, in an area called the raphe nuclei, but travels around the brain along the medial forebrain bundle activating the cortex, hippocampus, thalamus, hypothalamus and cerebellum. Also, it is released in the Caudal sertonin nucli, so as to have effect on the spinal cord. In the peripherial nervous system (such as in the gut wall) serotonin regulates vascular tone.
dopamine
modulates two systems: the brain's reward mechanism, and movement control.

Neurotransmitters that have these types of specific actions are often targeted by drugs
cocaine
blocks the reuptake of dopamine, leaving these neurotransmitters in the synaptic gap longer.
prozac
serotonin reuptake inhibitor, hence potentiating its effect. AMPT prevents the conversion of tyrosine to L-DOPA, the precursor to dopamine; reserpine prevents dopamine storage within vesicles; and deprenyl inhibits monoamine oxidase (MAO)-B and thus increases dopamine levels.
common nt
Amino acids
Aspartate
Glutamate (Glu)
γ-Aminobutyric acid (GABA)
Glycine (Gly)
[edit]
Acetylcholines
Acetylcholine (Ach)
[edit]
Monoamines
From phenylalanine and tyrosine (catecholamines, in the order of their synthesis):
Dopamine (DA)
Norepinephrine (noradrenaline) (NE)
Epinephrine (adrenaline) (Epi)
Octopamine
Tyramine
Phenylethanolamine
From tryptophan:
Serotonin (5-hydroxytryptamine, 5-HT)
Melatonin (Mel) (derived from serotonin, but not a monoamine)
From histidine:
Histamine (H)
[edit]
Polypeptides (neuropeptides)
Bombesin
Gastrin releasing peptide (GRP)
Gastrins
Gastrin
Cholecystokinin (CCK)
Neurohypophyseals
Vasopressin
Oxytocin
Neurophysin I
Neurophysin II
Neuropeptide Y
Neuropeptide Y (NY)
Pancreatic polypeptide (PP)
Peptide YY (PYY)
Opioids
Corticotropin (adrenocorticotropic hormone, ACTH)
Beta-lipotropin
Dynorphin
Endorphin
Enkephaline
Leumorphin
Secretins
Secretin
Motilin
Glucagon
Vasoactive intestinal peptide (VIP)
Growth hormone-releasing factor (GRF)
Somatostatins
Somatostatin
Tachykinins
Neurokinin A
Neurokinin B
Neuropeptide A
Neuropeptide gamma
Substance P
[edit]
Other neurotransmitters
Nitric oxide (NO)
Carbon monoxide (CO)
Anandamide
Dimethyltryptamine