Neurotransmitter

Neurotransmitters are endogenous chemicals (substances are those that originate from within an organism, tissue, or cell) that transmit signals across a synapse from one neuron (brain cell) to another 'target' neuron.

1. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane in the axon terminal, on the presynaptic side of a synapse.

2. Neurotransmitters are released into and diffuse across the synaptic cleft (a small space), where they bind to specific receptors in the membrane on the postsynaptic side of the synapse.

3. Most neurotransmitters are about the size of a single amino acid, but some neurotransmitters may be the size of larger proteins or peptides. (a neurotransmitter is available only briefly-before rapid deactivation-to bind to the postsynaptic receptors)

4. A neurotransmitter is released at the presynaptic terminal, in response to a threshold action potential or graded electrical potential.

5. Binding of neurotransmitters may influence the postsynaptic neuron in either an inhibitory or excitatory way.

There are many different ways to classify neurotransmitters

Dividing them into amino acids, peptides, and monoamines is sufficient for some classification purposes.

Major neurotransmitters:

Amino acid:

1. Glutamate:It is an important neurotransmitter that plays a key role in long-term potentiation and is important for learning

and memory. Glutamate is the most abundant excitatory neurotransmitter in the vertebrate nervous system.

2. Aspartate: It is a metabolite in the urea cycle and participates in gluconeogenesis. It carries reducing equivalents in the malate-aspartate shuttle, which utilizes the ready interconversion of aspartate and oxaloacetate, which is the oxidized (dehydrogenated) derivative of malic acid.

3. D-Serine: Serine plays an important role in the catalytic function of many enzymes. It has been shown to occur in the active sites of chymotrypsin, trypsin, and many other enzymes.

4. GABA: It acts at inhibitory synapses in the brain by binding to specific transmembrane receptors in the plasma membrane of both pre- and postsynaptic neuronal processes.

5. Glycine: Glycine is an inhibitory neurotransmitter in the central nervous system, especially in the spinal cord, brainstem, and retina.

Monoamine and Biogenic amine:

6. Dopamine: Inside the brain, dopamine plays important roles in motor control, motivation, arousal, cognition, and reward, as well as a number of basic lower-level functions including lactation, sexual gratification, and nausea.

7. Norepinephrine (noradrenaline; NE, NA): One of the most important functions of norepinephrine is its role as the neurotransmitter released from the sympathetic neurons to affect the heart.

8. Epinephrine (adrenaline): Epinephrine remains a useful medicine for several emergency indications.

9. Histamine: Although histamine is small compared to other biological molecules. It is known to be involved in 23 different physiological functions.

10. Serotonin: It is found in all bilateral animals. It is used to regulate intestinal movements. Its more function is to regulation of mood, appetite, and sleep. Serotonin also has

some cognitive functions, including memory and learning.

Trace amines:

11. Phenethylamine: Its functions as a neuromodulator or neurotransmitter in the mammalian central nervous system.

12. N-Methylphenethylamine: It in human urine and is produced by phenylethanolamine N-methyltransferase with phenethylamine as a substrate.

Peptide:

13. Acetylcholine: Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS). It acts on both the peripheral nervous system (activates muscles) and central nervous system (neuromodulator: process by which a given neuron uses one or more neurotransmitters to regulate diverse populations of neurons ) and is the only neurotransmitter used in the motor division of the somatic nervous system. Acetylcholine is also the principal neurotransmitter in all autonomic ganglia. In cardiac tissue

acetylcholine neurotransmission has an inhibitory effect, which lowers heart rate. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions in skeletal muscle.

14. Adenosine: It plays an important role in biochemical processes, such as energy transfer . It also plays a role in regulation of blood flow to various organs through vasodilation. It is also an inhibitory neurotransmitter, believed to play a role in promoting sleep and suppressing arousal.

acetylcholine neurotransmission has an inhibitory effect, which lowers heart rate. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions in skeletal muscle.

14. Adenosine: It plays an important role in biochemical processes, such as energy transfer . It also plays a role in regulation of blood flow to various organs through vasodilation. It is also an inhibitory neurotransmitter, believed to play a role in promoting sleep and suppressing arousal.