The phenomenon of the existence of our mind and consciousness is brought about by the fact that all functions elicited by the human body is brought about by complex neurochemical functioning of the brain (Frisch and Frisch 15). The brain is the master organ because it controls the functions of other organs. From the various movements done by our muscles, the different sensations we experience as well as the emotions we feel are made possible by the numerous processes being undergone by the brain (Frisch and Frisch 15). The brain is made up of different parts that are responsible in generating the functions of the brain.
These different components of the brain are important for they act hand- in- hand so that the brain can perform its proper functions. The brain controls the central nervous system via the cranial nerves, spinal cord and the peripheral nervous system (Frisch and Frisch 16). It is accountable for different voluntary and involuntary movements such as perception, behaviors, reflexes, instincts, emotions and thinking. Within the brain, there is the presence of several neurotransmitters. These neurotransmitters act as messengers that carry out and deliver the messages between neurons.
Their main functions are to relay, increase and adjust signals between the brain cells and other cells. They are located at the synapse of each neuron (Luckman 651). There are many types of neurotransmitters present in the brain. Their major divisions are amino acids, peptides and monoamines. Some of the more popular types of neurotransmitters are acetylcholine, epinephrine, serotonin and dopamine. Among these mentioned neurotransmitters, probably the one which produces many various effects is dopamine (Frisch and Frisch 16). Dopamine is a neurotransmitter which is a derivative of the amino acid tyrosine.
It is produced by neurons located at the Substantia Nigra, the part of the brain also known as Black Substance. The Substantia Nigra is found at the Basal Ganglia which are group of structures in the midbrain (Luckman 651). Dopamine is a monoamine formed by the decarboxylation of dopa and is very essential to the normal functioning of the central nervous system. Decarboxylation starts when tyrosine is changed to from dopa that in turn removes carbon dioxide from dopa to form dopamine. Dopamine is responsible for many vital brain functions. The dendrites of dopamine affect various regions of the bran thus controlling different functions.
Dopamine influences a wide variety of brain processes. These brain processes have important role in behavior and cognition, motor activity, motivation and reward, sleep, mood, attention, learning, perception of pain and pleasure, and regulation of milk production (Luckman 652). Dopamine is a sympathomimetic catecholamine. It exhibits alpha and beta adrenergic agonism. Dopamine can have either an excitatory or inhibitory effects. It can either bring about action potential or inhibit it. Dopamine travels via the presynaptic going to the postsynaptic neuron.
The abnormal levels of dopamine the brain can cause massive destruction to the brain thus causing enormous deterioration in functions influenced by dopamine. The kind of deterioration experienced by the human body depends on the part of the brain which has an abnormal level of dopamine. The Frontal Lobes In the frontal lobes, dopamine controls a variety of neurocognitve functions. It controls the flow of information to the other parts of the brain. Dopamine disorders in this area of the brain result in different neurocognitve dysfunctions that usually affect memory, attention and problem solving.
This is because these functions are greatly related to the mesocortical dopamine pathway. Other organs Dopamine plays a significant role in the different systems of the body. Some of these are the cardiovascular system, excretory system, reproductive system and central nervous system. Dopamine is useful in the management of low cardiac output states. This is associated with renal disorders like cardiogenic or hypovolemic shock. Dopamine also has an effect in the release of norepinephrine, a neurotransmitter that contributes to the functions of the heart. The usual effect of dopamine to the heart is the increase in systolic and pulse pressure.
It produces a positive effect on the myocardium which results in increased heart rate and contractility (Luckman 652). Pleasure System Dopamine is commonly associated with the “pleasure system” of the brain. Dopamine provides the feeling of enjoyment and motivation to do things or keep on doing certain activities. Dopamine is also released by different rewarding experiences such as food and sex and other stimuli associated with them (Luckman 652). Regulating Milk Production Dopamine is the primary regulator of the secretion of prolactin from the anterior pituitary gland.
Dopamine produced by the neurons in the hypothalamus is secreted in blood vessels that supply the pituitary glands. The lactotrope cells are the ones responsible in producing prolactin. With the absence of dopamine, these cells continue to produce prolactin. However, if dopamine is secreted by the neurons in the hypothalamus, the production of prolactin is inhibited. The secretion of dopamine is usually signaled by stimuli that dictated the body to stop producing milk (Luckman 62). Incentive Salience There have been many quandaries raised by different researchers on the effect of dopamine in experiencing pleasure.
There are those who believe that dopamine is more closely related to anticipatory desire and motivation than pleasure. This is the issue raised as wanting versus liking. Researchers who oppose the liking side believe that dopamine is released by the brain when it anticipates stimuli that arouse its craving. Dopamine is not released when unpleasant stimuli is encountered, thus it motivates the body to avoid this unpleasant stimuli (Luckman 6526). With this, dopamine is believed to influence the priority or level of desire and importance of stimuli. Reward- seeking Behavior
Dopamine has been shown to have an effect in the control of movements and signaling error in prediction of reward, motivation and cognition. Dopamine is associated with reward seeking behaviors such as approach, consumption, habits and addiction. There are researches that suggest that the dopaminergic neurons secrete dopamine as a consequence of the anticipation of a reward. This is because the result of their findings is that when there is an increase in reward, there is also an increase in the secretion of dopamine. Sociability Low D2 receptor-binding is found in people who experiences social anxiety.
This closely binds dopamine with social functioning. Social withdrawal and apathy are thought to be linked decreased dopamine levels in certain parts of the brain. Thus, if there is a low level of dopamine, a person can isolate himself and withdraw himself from others. And, if there is an abnormal elevation of dopamine, a person can become hypersocial, hyperactive and hypersexual (Luckman, 653). Animal Studies The studies made on the effects of dopamine to certain psychological drives were performed on animals. One study that was conducted made use of rats as its subjects.
These rats were depleted of dopamine up to 99 percent. Because of this enormous decrease in the percentage of the presence of dopamine in their system, the rats could no longer eat by their own will. However, when they were given food and fed, they ate retaining the same expressions for their like or dislike of the food given. Because of the result of the study, the researchers concluded that the reduction of dopamine did not decrease the rats’ consummatory pleasure. It only decreased the rats’ desire to eat (Luckman 653). Creative Drive and Motivation
Another aspect found to be affected by the neurotransmitter dopamine is creative drive and motivation. The increase in dopamine levels at the mesolimbic pathway increases the general arousal and goal directed behaviors. The study also showed that there is an increase in dopamine levels during activities such as hobbies that are found to release creativity. Drugs Associated with Dopamine and drug Addiction There are many drugs associated with dopamine. Some bring synergistic effect, or protagonist effect or others antagonistic effect. In humans, there are drugs that reduce the effect dopamine.
These drugs are mostly prescribed when the patient demonstrates behaviors which are indicators of high dopamine levels such as hyperactivity. Drugs like neuroleptics have been shown to reduce motivation and to reduce the possibility to experience pleasure. The transmission of Opioid and cannabinoid may modulate the consummatory pleasure and food palatability or food liking. This is because they alter the effect of dopamine which is finding pleasure in food. A study also revealed that sexual behaviors in male rats were decreased when the dopamine receptors were disrupted.
An example of this dopamine receptor blocker is cocaine. Cocaine acts by inhibiting the uptake of dopamine. However, cocaine inhibits the use of dopamine thus causing an oversupply of dopamine neurotransmitters. Because of this, dopamine levels in the synapse are too overwhelming causing drug induced psychosis or schizophrenia (Frisch and Frisch 364). Behavior Disorders Dopamine also has several effects on mental processes such as cognition and perception. With this, alterations in the dopamine levels in the brain can also cause an alteration in these mental processes. I. ADHD (Attention Deficit Hyperactive Disorder)
Attention deficit hyperactive disorder is a disorder connected with dopamine levels. This is because the increase in dopamine levels can result in behaviors that are manifestations of the disorder such as hyperactivity, lack of focus, and hypersexuality (Coleman, Butcher and Carsson 368). II. Schizophrenia There were various researches done on the relationship of dopamine levels and schizophrenia. The dopamine hypothesis or the dopamine hypothesis of psychosis is a theory that attributes symptoms of schizophrenia to the altered and elevated dopaminergic signal transduction.
Researchers were able to link these because many antipsychotics contain dopamine antagonistic effects. However, the theory did not conclude that it is the sole factor responsible for the disease (Broyles, Barry and Evans 644). Parkinson’s disease Dopamine is a vital to the way the brain control the body’s movements. It is important part of the basal ganglia. The decrease in dopamine, specifically the death of neurons containing dopamine, causes Parkinson’s disease. This is a movement disorder characterized by impairment in speech and motor skills such as muscle rigidity and tremors (Luckman 370).
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