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Brain Injury and Neurotransmitters


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Brain Injury and Neurotransmitters

Executive Summary

The Human brain is a complex structure that serves as a powerhouse in controlling physiological and cognitive activities in human body. This structure is composed of four major parts that include; the cerebellum, cerebrum, cerebral cortex, and the brain stem. Moreover, the human brain also contains billions of neurological connections that work together in order for these functions to take place. Mesencephalon part of the brain is as well as the pons, myelencephalon, and medulla oblongata collectively make up the brain stem, which links the fore and the hind brain with the spinal cord. Mesencephalon is made up of various parts such as quadrigemina, substantia nigra, grey matter, red nucleus, inferior and superior colliculus, tegmentum, among others. Each of these parts have its function, such as controlling hearing senses, sight, addiction, learning, movement, heart rate, breathing, swallowing, digestion, among others. When any of these parts is injured, either as a result of an accident, disease infection or abuse of drugs, its associated functions, and sometimes the functions of other parts may be impaired. A good example is an injury that might occur to the anterior and superior pair of quadrigemina, which controls the sense of sight. This injury may result to impaired vision, as well as the functioning of the inferior and posterior parts of quadrigemia, and that of tegmentum. Consecutively, an injury to the substantia nigra may result to low or high production of the neurotransmitter dopamine, and this negatively affects the mental health of an individual. In most cases, brain injuries are permanent and, therefore, the damage might be irreversible.


The Human brain is a complex and fundamental structure in the human body, which acts as a powerhouse and a control centre for numerous body functions. This structure facilitates complicated and vital psychological and physiological body functions such as personality, mobility, consciousness, emotion, breathing, digestion, and reasoning, among others. Nevertheless, this structure is unique in terms of its functionality since it possesses billions of neurological connections, which work as a team in order for these functions to happen. Moreover, this structure is made of four primary parts; brainstem, cerebral cortex, cerebrum, and cerebellum (Schünke et al. 2006). Each of these parts has other parts that are responsible for various functions. However, when a brain injury occurs, it usually disrupts a myriad of neurological connections, which results to the impairment of various functions. Apparently, function impairment may not only occur at the point where injury has occurred, but also many other areas that relate to the affected brain area. This paper pays high attention to the analysis of how an individual`s mental functioning is affected when an injury occurs to the mesencephalon part of the brain, and how lack or having too much neurotransmitter dopamine can affect an individual`s mental health.

How an injury to the mesencephalon part of the brain might affect an individual`s mental functioning

Mesencephalon or mid-brain acts as a linkage that connects fore-brain and the hind-brain. In addition, mesencephalon, together with other parts such as medulla oblongata, myelencephalon, and metencephalon (pons) make up the brain stem, which is connected to the spinal cord at the back of the brain. The upper surface of mid brain is composed of four small and rounded eminences that are collectively known as quadrigemina, while the interior structure is made up of grey matter (which surrounds the aqueduct of sytivius), grey nuclei, susbtantia nigra, and a red nucleus (Schünke et al. 2006). The quadrigemina is arranged in two pairs; the anterior and superior pair, and the posterior and inferior pair. The first pair is responsible for controlling the sense of sight while the posterior pair is responsible for the sense of hearing. Consecutively, the mid brain has superior and inferior colliculus on the anterior side, which are mainly responsible for analyzing and detecting auditory stimuli. This, together with inferior and posterior pair of quadrigemina, helps an individual to locate the source of various sounds, as well as to correlate them. Beneath the colliculi is the Tegmentum, which regulates autonomic functions such as breathing rate, heart rate, and digestion. The red nucleus in the mid brain is responsible for motor coordination, while the substantia nigra contributes in the movement, addiction and learning in the human body (InnovateUs, 2013).

Generally, mesencephalon part of the brain is responsible for controlling the respiratory muscles, controlling pharyngeal, controlling vocal cords, palate, mandibles, lips, tongue, hearing, sight, among others. Injury to any of the various parts that make up the mid brain, either due to abuse of drugs or disease infection, can alter their associated functions, as well as functions of other parts of the brain. For example, an injury to the colliculus can make an individual fail to recognize the strength and source of sounds, as this part is responsible for controlling hearing. Other adverse effects that might occur when mid brain is injured include; dysphagia (inability of swallowing food and water), breathing problems, arrhythmia (irregular heartbeat), lack of concentration, among others (InnovateUs, 2013).


How lack or having too much neurotransmitter dopamine can affect an individual`s mental health

Dopamine is a neurotransmitter that has a strong influence to both the motor and think parts of the brain. This neurotransmitter is produced at the susbtantia nigra, located in the mesencephalon. Low levels of this neurotransmitter impair an individual`s ability to concentrate on his or her environment, task, conversations, or activities. In most cases, low levels of dopamine are associated with Attention-Deficit Hyperactivity Disorder (ADHD). On the other hand, high levels of this neurotransmitter make an individual be hyper-stimulated by his or her environment. An individual may feel energized or excited, paranoid and suspicious to his or her immediate environment. Loud sounds that an individual hear suddenly change to auditory hallucinations (Carver, 2002). An individual starts to feel inner thoughts as if they are outside his or her body.


It is, therefore, evident that an injury to mesencephalon part of the brain can negatively affect an individual`s mental functioning. Any part of the brain is highly sensitive and, therefore, any injury may not only affect the functions of the affected part, but also the functions of other parts of the brain. Moreover, low and high levels of dopamine also have negative adverse effects to an individual`s mental health.


Carver, J. M., (2002).The “Chemical Imbalance” in Mental Health Problems. Retrieved from,

InnovateUs, (2013). What is the function of the Midbrain ? retrieved from,

Schünke, M., Schulte, E., Schumacher, U., Ross, L. M., Lamperti, E. D., & Taub, E. (2006). Thieme atlas of anatomy. Stuttgart ; New York: Thieme.