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Neurons expressing certain types of neurotransmitters sometimes form distinct systems, where activation of the system affects large volumes of the brain, called volume transmission. Major neurotransmitter systems include the noradrenaline (norepinephrine) system, the dopamine system, the serotonin system, and the cholinergic system, among others.
A neurotransmitter is a type of molecule that carries signals between neurons (nerve cells) at synapses in the nervous system The main article for this category is Neurotransmitters . Wikimedia Commons has media related to Neurotransmitters .
Once released, a neurotransmitter enters the synapse and encounters receptors. Neurotransmitter receptors can either be ionotropic or g protein coupled. Ionotropic receptors allow for ions to pass through when agonized by a ligand. The main model involves a receptor composed of multiple subunits that allow for coordination of ion preference.
In fact, there are over a hundred known neurotransmitters, and many of them have multiple types of receptors. [44] Many synapses use more than one neurotransmitter—a common arrangement is for a synapse to use one fast-acting small-molecule neurotransmitter such as glutamate or GABA , along with one or more peptide neurotransmitters that play ...
Monoaminergic systems, i.e., the networks of neurons that use monoamine neurotransmitters, are involved in the regulation of processes such as emotion, arousal, and certain types of memory. It has also been found that monoamine neurotransmitters play an important role in the secretion and production of neurotrophin-3 by astrocytes, a chemical ...
Neuromodulation is the physiological process by which a given neuron uses one or more chemicals to regulate diverse populations of neurons. Neuromodulators typically bind to metabotropic, G-protein coupled receptors (GPCRs) to initiate a second messenger signaling cascade that induces a broad, long-lasting signal.
Over the first half of the 20th century, two main proposals were made to explain this phenomenon: There were (at least) two different types of neurotransmitters released from sympathetic nerve terminals, or; There were (at least) two different types of detector mechanisms for a single neurotransmitter.
The major types of gliotransmitters released from astrocytes include glutamate and ATP. Glutamate is the major excitatory neurotransmitter within the central nervous system that can also be defined as a gliotransmitter due to its ability to increase cytosolic Ca 2+ concentrations in astrocytes.