What Is the Role of Neurotransmitters in the Brain?

Cerebral neurotransmitters are chemical substances that produce information from the presynapse to the postsynapse of the brain nerves (producing synaptic potentials). Transmitters are synthesized by the cells, and then transported to synaptic vesicles in the pre-protruding pre-cells. Action potentials are converted from calcium channels to the release of transmitters at the distal end, diffuse through the synaptic space, and specifically act on post-synaptic cells. Receptors on neurons or effector cells.

Neurons are interconnected with tightly fitting connections, called synapses. In most cases, the connections between neurons are mediated by chemicals called neurotransmitters. When an electrical impulse in the transmitting cell reaches the synapse, the small vesicles of the neurotransmitter release the neurotransmitter into the synaptic space through the membrane, and then the neurotransmitter binds to a special receptor on the surface of the target cell, thereby inducing a certain amount of The current strengthens or suppresses the formation of action potentials. Each neuron is related to whether the excitatory or inhibitory input is balanced, and therefore also regulates the discharge of its action potential ^[1]

To determine a chemical substance as a neurotransmitter, the following conditions must be met:

1. Have synthesizing this transmitter in presynaptic neurons

Chemical structure can be divided into different types of transmitters. Although the number or proportion of certain transmitters in the human brain is very different from other animals, there does not seem to be anything unique. In fact, the neurochemicals found in mammalian brains and the mechanisms by which they perform functions appear to be very similar to those observed in invertebrate brains. This means that the principles obtained through the study of the invertebrate nervous system can be widely applied to higher animals, including humans ^[1]

The transmission of neurotransmitters in the brain is the most complicated, and there are about hundreds of central neurotransmitters involved in human mental activity ^[3]

Two or more transmitters (including modulators) coexist in the same neuron. This phenomenon is called neurotransmitter co-existence, and its significance is to coordinate certain physiological functions. For example, cat salivary glands are dominated by parasympathetic and sympathetic nerves. Parasympathetic nerves contain acetylcholine and vasoactive intestinal peptide. The former can cause salivary secretion; the latter can relax blood vessels, increase blood supply to salivary glands, and enhance the affinity of cholinergic receptors on salivary glands. Together, the salivary glands secrete a large amount of thin saliva. Sympathetic nerves contain norepinephrine and neuropeptide Y. The former has the effect of promoting saliva secretion and reducing blood supply; the latter mainly shrinks blood vessels and reduces blood supply. The two work together to make the salivary glands secrete a small amount of viscous saliva. Before the coexistence of transmitters was discovered, British scientist Henry Hallett Dale proposed a view that only one neuron exists and releases the same transmitter through all its terminals. . This view is called the Dale's principle or Dale's law ^[4]

The metabolism of transmitters includes the steps of synthesis, storage, release, degradation, reuptake and resynthesis of transmitters. Both acetylcholine and amine transmitters are synthesized under the catalysis of related synthetases, and the synthesis process is mostly performed in the cytoplasm, and then stored in synaptic vesicles. Peptide transmitters are formed under the regulation of genes through processes such as ribosome translation and post-translational enzyme digestion. The binding of the transmitter to the receptor and its immediate effect are eliminated by means of enzymatic degradation and presynaptic reuptake. For example, acetylcholinesterase attached to the post-synaptic membrane can rapidly hydrolyze acetylcholine into choline and acetic acid, and the produced choline is reabsorbed back into the periphery for re-synthesis of new transmitters. Elimination of norepinephrine is mainly through reuptake of the periphery, and a small amount is inactivated by enzymatic hydrolysis. The elimination of peptide transmitters mainly depends on enzymatic degradation ^[4] .