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Neurotransmitters (amino acid and biogenic amine), Acetylcholine (Excite…
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Glutamate (amino acid)
Within brain --> L-glutamate synthesized in presynaptic neurons by two sources: from glucose via krebs cycle or from glutamine synthesized in glial cells, transported into nerve cells, converted into glutamate by glutaminase.
Synaptic vesicles containing l-glutamate induced to exocytosis by depolarization of terminal end of presynaptic axon and by Ca2+ entering intercellular fluid
Glutamate binds with receptors in postsynaptic cell and promotes opening of chemically gated ion channels permeable to Na+ and Ca2+
After causing depolarization of postsynaptic cell glutamic acid is reabsorbed by presynaptic neuron, or taken up by glial cells and converted glutamine by glutamine synthetase.
Glutamate (and aspartate) are excitatory (EAA), bind to different receptor types with different activities, initiate fast EPSPs or slow EPSPs.
EAAs important for memory. Deficit = long term depression, Excess = neurotoxicity and brain damage - Huntington's, cerebral ischemia, epilepsy, hypoglycemia and AIDS.
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Glycine
simple amino acid, ubiquitous in human body, essentail in metabolism of protein, peptides, nucleic acids, porphyrins and bile salts.
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Dopamine
Neurons containing dopamine are primarily in midbrain, within substansia nigra - with some axons projecting into cerebral cortex where dopamine in involved in emotional responses - other axons project into basal ganglia where dopamine has inhibitory activity on autonomic movements - lending to stability and motor control. destruction of these neurons can lead to parkinson's.
Derived from tyrosine, synthesized in the liver from phenylalanine by phenylalanine hydroxylase, transported across BBB into dopaminergic neurons.
Absorption of tyrosine and tryptophan is regulated by other amino acids, certain conditions my diminish this.
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E and NE
Concentrated in adrenal medulla, secreted in response to sympathetic stimulation
Adrenal medullae are modified sympathetic ganglionic fibers and secrete E and NE directly into bloodstream.
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Serotonin (5-HT)
found in many cells that are not neurons - platelets, mast cells, enterochromaffin cells of intestinal musosa. Only 1% of serotonin produced in body is made in the brain and it can not pass BBB so brain must make it's own.
Synthesized in brain from dietary tryptophan (eggs, turkey, aged cheese).
TH (tryptophan hydroxylase) acts on tryptophan to complete hydroxylation into 5-hydroxytryptophan (5-HTP) which is then decarboxylated by amino acid decarboxylase (AADC) to form 5-hydroxytryptamine (5-H)
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