User:Mgjones2/Neurotransmitter

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Lead: A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. '''A neurotransmitter, alternatively known as a chemical transmitter or chemical messenger, refers to a group of chemical agents released by neurons. These substances play a vital role in stimulating neighboring neurons or muscle and gland cells, facilitating the transmission of impulses from one cell to another across the entire nervous system '''

Identification
There are four main criteria for identifying neurotransmitters: 


 * 1) The chemical must be synthesized in the neuron or otherwise be present in it.
 * 2) When the neuron is active, the chemical must be released and produce a response in some targets.
 * 3) The same response must be obtained when the chemical is experimentally placed on the target.
 * 4) A mechanism must exist for removing the chemical from its site of activation after its work is done.

To identify neurotransmitters, the following criteria are typically considered:

1. Synthesis: The chemical must be produced within the neuron or be present in it as a precursor molecule.

2. Release and Response: When the neuron is activated, the chemical must be released and elicit a response in target cells or neurons.

3. Experimental Response: Application of the chemical directly to the target cells should produce the same response observed when the chemical is naturally released from neurons.

4. Removal Mechanism: There must be a mechanism in place to remove the neurotransmitter from its site of action once its signaling role is complete.

Actions

 * Neurons form elaborate networks through which nerve impulses – action potentials – travel. Each neuron has as many as 15,000 connections with neighboring neurons.[citation needed] Neurons do not touch each other (except in the case of an electrical synapse through a gap junction); instead, neurons interact at contact points called synapses: a junction within two nerve cells, consisting of a miniature gap within which impulses are carried by a neurotransmitter. A neuron transports its information by way of a nerve impulse called an action potential. When an action potential arrives at the synapse's presynaptic terminal button, it may stimulate the release of neurotransmitters. These neurotransmitters are released into the synaptic cleft to bind onto the receptors of the postsynaptic membrane and influence another cell, either in an inhibitory or excitatory way. The next neuron may be connected to many more neurons, and if the total of excitatory influences minus inhibitory influences is great enough, it will also "fire". That is to say, it will create a new action potential at its axon hillock, releasing neurotransmitters and passing on the information to yet another neighboring neuron.[citation needed]
 * Neurons communicate with each other through synapses, specialized contact points where neurotransmitters transmit signals. When an action potential reaches the presynaptic terminal, the action potential can trigger the release of neurotransmitters into the synaptic cleft. These neurotransmitters then bind to receptors on the postsynaptic membrane, influencing the receiving neuron in either an inhibitory or excitatory manner. If the overall excitatory influences outweigh the inhibitory influences, the receiving neuron may generate its own action potential, continuing the transmission of information to the next neuron in the network. This process allows for the flow of information and the formation of complex neural networks. 
 * Norepinephrine which is synthesized in the central nervous system and sympathetic nerves, modulates the responses of the autonomic nervous system, the sleep patterns, focus and alertness. It is synthesized from tyrosine.
 * Norepinephrine is a member of the catecholamine classification of neurotransmitters. It is synthesized from the amino acid tyrosine. In the peripheral nervous system, one of the primary roles of norepinephrine is to stimulate the release of the stress hormone epinephrine (i.e. adrenaline) from the adrenal glands.
 * Epinephrine which is also synthesized from tyrosine is released in the adrenal glands and the brainstem. It plays a role in sleep, with one's ability to become and stay alert, and the fight-or-flight response.
 * Epinephrine, a neurotransmitter and hormone is synthesized from tyrosine. It is released from the adrenal glands and plays a role in the fight-or-flight response. Epinephrine has vasoconstrictive effects, which promote increased heart rate, blood pressure, energy mobilization. Vasoconstriction influences metabolism by promoting the breakdown of glucose released into the bloodstream. Epinephrine also has bronchodilation effects, which is the relaxing of airways.

Elimination
Astrocytes, a type of glial cell in the brain, actively contribute to synaptic communication through astrocytic diffusion or gliotransmission. Neuronal activity triggers an increase in astrocytic calcium levels, prompting the release of gliotransmitters, such as glutamate, ATP, and D-serine.These gliotransmitters diffuse into the extracellular space, interacting with nearby neurons and influencing synaptic transmission. By regulating extracellular neurotransmitter levels, astrocytes help maintain proper synaptic function. This bidirectional communication between astrocytes and neurons adds complexity to brain signaling, with implications for brain function and neurological disorders. Understanding astrocytic diffusion may lead to novel therapeutic strategies for neurological conditions.