The brain is an organ made up of cells known as neurons which communicate using chemical signals that involve neurotransmitters such as serotonin, norepinephrine, and dopamine. The turnover model, which is composed of five steps, explains the process neurotransmitters undergo in order for them to be released and have an effect. It is important to note that drugs specifically target one or more of these steps in order to be effective. The first step is biosynthesis, which is when the presynaptic cell synthesizes neurotransmitters when a precursor interacts with an enzyme. For example, when the precursor tyrosine interacts with the enzyme tyrosine hydroxylase, it becomes L-Dopa, and when that precursor interacts with the enzyme DOPA decarboxylase, the outcome is dopamine. Then, the second step is storage. This is when the neurotransmitters are stored in vesicles, which fuse to the membrane so they can be released. This release is the third step and it is called exocytosis. Exo- meaning outside, cyto- meaning cell and -sis referring to a process. In other words, the process in which a neurotransmitter is released outside of the cell. Neurotransmitters travel into the space between the presynaptic and postsynaptic cells, known as the synaptic cleft, where they bind to the receptors located in the postsynaptic cells. After they bind, the neurotransmitters have three options. The first one is that they can travel to the extracellular space, thus, becoming lost. The second option is the fourth step of enzymatic degradation. This refers to the fact that they can also be broken apart by enzymes, such as monoamine oxidase (MAO). The final option and the fifth step is reuptake, which describes how a neurotransmitter can be recycled by a protein known as a transporter that picks it up and returns it to the presynaptic cell where it can be reused later on. Another concept
The brain is an organ made up of cells known as neurons which communicate using chemical signals that involve neurotransmitters such as serotonin, norepinephrine, and dopamine. The turnover model, which is composed of five steps, explains the process neurotransmitters undergo in order for them to be released and have an effect. It is important to note that drugs specifically target one or more of these steps in order to be effective. The first step is biosynthesis, which is when the presynaptic cell synthesizes neurotransmitters when a precursor interacts with an enzyme. For example, when the precursor tyrosine interacts with the enzyme tyrosine hydroxylase, it becomes L-Dopa, and when that precursor interacts with the enzyme DOPA decarboxylase, the outcome is dopamine. Then, the second step is storage. This is when the neurotransmitters are stored in vesicles, which fuse to the membrane so they can be released. This release is the third step and it is called exocytosis. Exo- meaning outside, cyto- meaning cell and -sis referring to a process. In other words, the process in which a neurotransmitter is released outside of the cell. Neurotransmitters travel into the space between the presynaptic and postsynaptic cells, known as the synaptic cleft, where they bind to the receptors located in the postsynaptic cells. After they bind, the neurotransmitters have three options. The first one is that they can travel to the extracellular space, thus, becoming lost. The second option is the fourth step of enzymatic degradation. This refers to the fact that they can also be broken apart by enzymes, such as monoamine oxidase (MAO). The final option and the fifth step is reuptake, which describes how a neurotransmitter can be recycled by a protein known as a transporter that picks it up and returns it to the presynaptic cell where it can be reused later on. Another concept