W-2 Neurotransmitters

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Neurotransmitters (Serotonin)

Neurotransmitters are essentially the chemical messages that are involved in the transmission, balancing, and boosting of signals between the neurons and the target cells in the body (Jones et al., 2020). The target cells include; the muscles, glands as well as other neurons (Jones et al., 2020). Neurotransmitters usually convey the messages or signals by moving between the cells whereby they attach themselves to specific receptors contained in the target cells, which triggers an action in the receiving cells (Jones et al., 2020). 

Serotonin is one of the major neurotransmitters in the body that is involved in the transmission of messages or signals between neurons (Jones et al., 2020). Serotonin is also referred to as 5-hydroxytryptamine (5-HT) (Jones et al., 2020). This neurotransmitter is found mainly in the digestive system (Jones et al., 2020). However, it is also found in the central nervous system and blood platelets (Jones et al., 2020). Therefore, it influences a variety of physiological and physical functions. 

Functions of serotonin

Serotonin is mainly involved in the transmission of messages or signals between the neurons and the regulation of their intensity (Jones et al., 2020). Thus, it is involved in numerous bodily functions that include; regulation and stabilization of mood and emotions. This neurotransmitter also helps with eating, digestion, and sleeping (Jones et al., 2020). Serotonin contained in the brain is involved in the regulation of mood, anxiety, and happiness (Jones et al., 2020). For instance, the occurrence of low serotonin levels in the brain is associated with the development of depression. This neurotransmitter is found mainly in the digestive system and helps in controlling bowel function and movements (Jones et al., 2020). For instance, serotonin helps in normalizing bowel function and minimizing an individual’s appetite while eating, which helps them to know when they are full (Jones et al., 2020). 

Serotonin also helps in the regulation of sleep-wake cycles as well as the body clock (Jacobs & Fornal, 2019). This neurotransmitter is involved in the stimulation of brain parts that help in controlling sleep-wake cycles (Jones et al., 2020). For instance, the occurrence of sleep or waking usually depends on the brain part that is stimulated and the involved serotonin receptor (Jones et al., 2020). Additionally, serotonin plays a significant role in the clotting of blood and healing of wounds. For instance, the occurrence of tissue damages like cuts usually leads to the release of serotonin by the blood platelets that helps in the healing of wounds (Jones et al., 2020). This leads to increased levels of serotonin that result in the narrowing of arteries, which helps in the formation of blood clots and the healing of wounds. Moreover, this neurotransmitter plays a significant role in sexual function by influencing the intensity and frequency of an individual’s sexual feelings (Jones et al., 2020). For instance, the occurrence of low serotonin levels usually leads to an increased libido. On the other hand, the occurrence of increased serotonin levels usually results in decreased libido. Serotonin is also involved in the maintenance of bone health (Jones et al., 2020). For instance, the presence of increased serotonin levels in the bones may lead to the occurrence of osteoporosis. Overall, this neurotransmitter is involved in various functions of the body that include; the regulation of emotions and mood, and it also helps in the regulation of anxiety, depression, healing of wounds, maintenance of bone health, and stimulation of nausea (Jones et al., 2020). 

Pathway of origin and projections

The pathways of serotonin originate mainly from the caudal and rostral raphe nuclei (Ohmura et al., 2020). The serotonergic pathways that originate from the rostral raphe nuclei usually ascend to the limbic regions and cerebral cortex, and particularly they ascend to the basal ganglia (Ohmura et al., 2020). The major serotonin pathways that originate from the raphe nuclei (midbrain) and ascend to the forebrain include; the ventral tegmental radiations and the dorsal periventricular pathway (Ohmura et al., 2020). These pathways usually meet at the caudal hypothalamus. The projections to the hypothalamus, septum, and hippocampus originate mainly from the median raphe nuclei (Ohmura et al., 2020). The pathways that project into the subcortical, spinal, and cortical areas are usually involved in the regulation of motor activity (Ohmura et al., 2020). The serotonergic projects that originate in the caudal nuclei are usually involved in the regulation of emotions and mood. On the other hand, various descending pathways descend to the spinal cord or terminate at the medulla (Ohmura et al., 2020). Overall, the production of serotonin occurs mainly in the neurons that originate from the raphe nuclei situated in the brainstem’s midline (Ohmura et al., 2020). Most of the dorsal raphe, medial raphe, and rostral raphe nucleus usually innervate the central nervous system while the spinal cord is mainly innervated by the caudal raphe (Ohmura et al., 2020). 

Is serotonin neurotransmitter excitatory or inhibitory?

Serotonin is essentially an inhibitory neurotransmitter and is usually involved in the regulation of mood and emotions (Jones et al., 2020). It also helps in the regulation of various processes in the body that include; food digestion, sleep-wake cycle, blood clotting, and pain control. Inhibitory neurotransmitters like serotonin usually are associated with inhibitory effects on the receiving neuron or target cell by minimizing its possibility of firing any action potential (Jones et al., 2020). Inhibitory neurotransmitters usually lead to hyperpolarization of the receiving or target cells, which minimizes their threshold for the action potential (Jones et al., 2020). 

Behaviors associated with this neurotransmitter

This transmitter affects almost every part of the body and is involved in numerous essential functions and processes that occur in the body. Thus, imbalanced levels of serotonin can lead to the occurrence of various behavioral problems (Manchia et al., 2017). For instance, low serotonin levels may lead to the occurrence of suicidal behavior, anxiety, obsessive-compulsive disorder, and depression-related behaviors (Manchia et al., 2017). According to Manchia et al. (2017), most of the individuals suffering from depression are found to have low serotonin levels. Additionally, low serotonin levels may also lead to the occurrence of mood disorders like anxiety. Decreased serotonin levels are also associated with the occurrence of impulsive and aggressive behaviors (Çetin, Torun & Güney, 2017).

According to Çetin, Torun & Güney (2017), decreased levels of serotonin in an individual’s brain are associated with poor or inadequate cortex function that leads to the development of antisocial behaviors. On the other hand, increased serotonin levels may lead to the occurrence of various behavioral problems such as confusion, restlessness, and agitation (Manchia et al., 2017). Overall, serotonin is involved in various essential functions and affects almost every part of the body. Thus, imbalanced levels of serotonin may affect an individual’s emotional, mental, and physical wellbeing leading to the development of various emotional and behavioral problems (Manchia et al., 2017). 

Conclusion

Serotonin is one of the major neurotransmitters in the body that is involved in various functions and processes including; the regulation of regulation and stabilization of mood and emotions. This neurotransmitter also helps with eating, digestion, and sleeping. However, the presence of imbalanced levels of serotonin in the body may lead to the development of various emotional and behavioral problems like suicidal behavior, anxiety, obsessive-compulsive disorder, and depression-related behaviors (Manchia et al., 2017). 

References

Çetin, F. H., Torun, Y. T., & Güney, E. (2017). The Role of Serotonin in Aggression and Impulsiveness. Serotonin: A Chemical Messenger Between All Types of Living Cells, 241(10.5772).

Jacobs, B. L., & Fornal, C. A. (2019). An integrative role for serotonin in the central nervous system. In Handbook of Behavioral State Control (pp. 181-193). CRC Press.

Jones, L. A., Sun, E. W., Martin, A. M., & Keating, D. J. (2020). The ever-changing roles of serotonin. The International Journal of Biochemistry & Cell Biology, 125, 105776.

Manchia, M., Carpiniello, B., Valtorta, F., & Comai, S. (2017). Serotonin dysfunction, aggressive behavior, and mental illness: exploring the link using a dimensional approach. ACS chemical neuroscience, 8(5), 961-972.

Ohmura, Y., Tsutsui-Kimura, I., Sasamori, H., Nebuka, M., Nishitani, N., Tanaka, K. F., ... & Yoshioka, M. (2020). Different roles of distinct serotonergic pathways in anxiety-like behavior, antidepressant-like, and anti-impulsive effects. Neuropharmacology, 167, 107703.