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Small Molecule NeurotransmittersSerotonin, Dopamine, Norepinephrine, And Acetylcholine
Neurotransmitters are chemicals released by neurons for communication within the nervous system. Small molecules are one of the many that participate as signals.
The nervous system relies on chemicals for communication amongst the various neurons and nerve fibers that make up the central and peripheral nervous system. These chemicals allow the brain to interpret signals from the periphery and to respond mechanically. They are also extremely important in less obvious reactions, such as emotion, desire, blood pressure, pain, and consciousness. NeurotransmittersNeurotransmitters are secreted by neurons at the synapses, particularly the presynaptic terminal. They will be taken up by the next neuron if receptors are present. Excitation or inhibition occurs depending on if polarization or hyperpolarization follows uptake, respectively. This is the postsynaptic potential. Neurotransmitter release is signaled by depolarization. If a neurotransmitter is not taken up by the postsynaptic neuron it may diffuse away from the synaptic cleft, be degraded or deactivated by enzymes, be taken up by glial cells (astrocytes), or experience reuptake. Neurotransmitter reuptake is when the molecule is removed from the synaptic cleft by the neuron that released it. Serotonin (5-HT)Serotonin is a monoamine produced from the amino acid tryptophan by neurons in the central nervous system, called serotonergic neurons, and by specialized cells in the gastrointestinal tract. The system is believed to play a major role in mood, sexuality, and emotion, making the serotonin system a target of antidepressant treatment and studies of human consciousness. It is also believed to have a role in temperature and nausea. Dopamine (DA)Dopamine is a type of molecule called phenylethamine and activates five different receptors in the brain, each associated with different responses. Dopamine is produced in the substantia nigra of the brain and the hypothalamus. The dopamine system is associated with motor activity, behavior and cognition, memory, sleep, mood, and attention, as well as prolactin secretion from the pituitary. Norepinephrine is a catecholamine derived from dopamine that binds to adrenergic receptors. The norepinephrine system, also known as the noradrenalin system, is associated with arousal and reward. It also includes the derivative epinephrine, known better as adrenalin. Norepinephrine is considered to be a stress hormone, which promotes the fight or flight response resulting in increases in heart rate and mobilization of glucose stores to the muscles. These neurochemicals are often used as drugs to increase blood pressure. Acetylcholine (ACh)Acetylcholine is the neurochemical utilized at cholinergic synapses. The cholinergic system includes the parasympathetic nervous system as well as neuromuscular junctions, the brain stem, and the basal forebrain. Choline is actually taken up by the neuron, but combines with acetyl CoA to produce acetylcholine in the presence of choline acetyltransferase. Acetylcholine was the first neurotransmitter to be discovered and assists in digestion. It is the main neurotransmitter controlling the muscles. ReferencesBest, Ben. Brain Neurotransmitters, Ch 10. University of Washington Neuroscience for Kids website
The copyright of the article Small Molecule Neurotransmitters in Nervous System is owned by Alicia Mae Prater. Permission to republish Small Molecule Neurotransmitters in print or online must be granted by the author in writing.
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