The nervous system is one of the most important ones of the human body which supervises and reacts to changes in the internal and external environment, maintaining homeostasis in our body (Farley A 2014). It has other functions, as perception, behavior, memory and controlling voluntary and involuntary movements. But its most significant function is to carry information from one place to other in the body (Tortora and Derrickson 2013). The nervous system has two major divisions: The Central Nervous System (CNS), which is composed by the brain and the spinal cord, and The Peripheral Nervous System (PNS), which is made up of all the rest of the nervous tissue that is not in the CNS (Broad, 2004) (Farley A 2014).
The Central Nervous System consists of the brain and spinal cord. The brain is composed of neurons and neuroglia (nutritive structures), and its main function is to incorporate sensory information and control involuntary functions, such as respiration. It also controls motor responses and has an important role in learning. (Farley A 2014). The spinal cord is the communication center between the CNS and the PNS; it has also other important functions that range from the most basic, as walking movements, to the most complex, as motor reflexes in order to prevent the body from suffering from painful situations without the input of the brain (Matic 2014). An example of this is when you put your hand on a hot stove, and the stimuli in order to have a faster response goes to the spinal cord activating the motor neurons to take your hand away from danger; it happens because if that information has to go to the brain in order to process it and then activate your motor neurons your hand will surely burn for longer, making it worse
The Peripheral Nervous System is mainly formed by nerves and has two subdivisions: Somatic Nervous System (SNS) and Autonomic Nervous System (ANS). The SNS is formed by the sensory and motor nerves; the former carries information received from outside stimuli to the brain and spinal cord, while the latter communicates with muscles to generate voluntary movement (Farley A 2014). On the other hand, the ANS is responsible for controlling the body’s involuntary actions such as breathing, blood pressure, and temperature regulation (Farley A 2014). This system is subdivided in the sympathetic nervous system which is responsible in preparing the body for a “fight-or-flight” situation, and the parasympathetic nervous system that stabilizes all the body functions in order to bring it to a “rest-and-digest” state. ((Farley A 2014)
Although the Nervous System is well divided and organized in different organs and nerves, it’s important to recall that its functional unit is the neuron. Neurons are specialized cells that communicate between themselves across electrical and chemical messages. (Farley A 2014) They are the building blocks of the nervous system and have direct communication through it, sending sensory information to its parts. The three main parts that compose the neurons main structures are: the cell body, which contains the nucleus, and its function is to synthesize proteins, and contains grey matter; dendrites, responsible for receiving information and sending it to the cell body; and axons, which are in charge of taking away the information from the cell body (Farley A 2014). Information between neurons can be transmitted either using chemical or electrical signals. The former is done with the use of neurotransmitters and occurs in a junction called the synapsis, where nerve impulses pass from the dendrites of a neuron to the axon of the following neuron; while the latter is a consequence of ions movement across the nerve cell membrane. (Farley A 2014)
There are several diseases that can affect the Nervous System alter its functions in the human body. The main three that are going to be discussed in this paper are Multiple Sclerosis, Synesthesia and Alzheimer’s Disease. By reading what they are, its causes, consequences, and treatments the reader will learn more about how damaging they are and how they can change one’s life.
Multiple Sclerosis (MS), according to Sadeghi Bahmani, can be defined as an “autoimmune, chronic, inflammatory, demyelinating neurodegenerative disease” that affects an amount close to two million of all the population in the world (Sadeghi Bahmani D 2017). This disease can also be characterized by degenerate mobility, loss the control of bladder, and also to slower or diminish one’s cognitive processing (Reich, D 2017). Multiple Sclerosis lesions can be distinguished in an MRI by seeing central areas of demyelination, inflammation, and glial reaction in the white matter located in the brain or spinal cord (Reich, D 2017).
There are several causes that can lead to suffering this disease. First, genetics, it has been proved that around 2-4% of people that have a direct relative that suffers from this disease has a chance of getting it (Reich, D 2017). According to studies done in the past, around 200 different gene combinations can lead to the person having Multiple Sclerosis. Another important cause is the environment, there’s some relation between mild weather areas and the exposure of sunlight (vitamin D increase) and MS (Reich, D 2017). In addition to the environmental factors, the exposure of substances as tobacco, or diseases as obesity and mononucleosis can increase your risk of acquiring this neurodegenerative disease. Also, research suggests a not yet proved correlation between coming in contact with Epstein-Barr (found in mononucleosis), among other viruses and being affected by Multiple Sclerosis (Reich, D 2017).
This disease of the nervous system has several effects on the human daily development such as monocular visual loss due to optic neuritis, limb sensory loss, double vision, or ataxia due to a cerebellar lesion. impaired ambulation, loss of bladder control, and slowed cognitive processing (Reich, D 2017). Additionally, with the pass of time (between 10 to 20 years after acquiring this disease), it can lead to the diminishment of mental and motor capability(Reich, D 2017).
Sadly, there’s no way to cure or prevent being affected by this disease, but scientists have come with more than a dozen different treatments with the goal of decreasing the recurrence of episodes. According to the Food and Drug Administration, there are 15 existing and approved medications that can use in order to modify how this disease changes its course along the human body. Some of them are interferon beta, glatiramer acetate the monoclonal and antibodies such as natalizumab, alemtuzumab, daclizumab, and ocrelizumab, among others (Reich, D 2017).
Synesthesia is a disease of the Nervous System in which a stimulus also activate a separate and different sensory stimulus, meaning that a sound may not only be heard by the person but it could also have flavor, smell or even physical sensation (Robinson 2015). According to Caleb Robinson, this disease can be defined with the literal meaning of “experiencing together.” An example given by Robinson is the one of a person who suffers from sound-color synesthesia, when hearing the sound of a violin playing, this person could also generate an unexpected color or even when hearing the sound of a furnace which can evoke to that person the shades of red color (Robinson 2015).
Grapheme-color synesthesia has been proven to be the most common type of all the Synesthesia types, it happens to around 45 to 65% of the population that experience synesthetic sensations (Robinson 2015). Also, it has been shown that genetics play a big role when it relates to containing this disorder, around 42% of patients affected by Synesthesia have a direct relative who is also suffering from it. It is equally important to add that the main factor that causes Synesthesia is the fact that there is a cross-wiring between the area V4 of the visual cortex and fusiform gyrus which respectively, which are in charge on color perception and color and word material (Robinson 2015).
The main consequences of Synesthesia vary depending on the type of Synesthesia you’re suffering from, it can be that a color emerges from a written word, such as that sounds arouse a taste or there are also cases where one stimulus can be related with a physical sensation (Robinson 2015). This disorder even if it doesn’t any have health concerns, it can affect a person’s daily life with social concerns as being ridiculed and being part of stereotypes given to them. Also, some people that suffer from this disease can be affected by the fact that their math abilities and object perception is not as good as non-synesthetic people ability.
There’s no treatment for this disease, even though people have tried with types of hypnosis, which eliminates their unconscious mind in order to prevent the involuntary synesthetic perceptions produced by the disease. Others, just get used to this disorder and learn how to handle it in their daily activities.
Alzheimer’s disease can be defined as a chronic disease that affects elderly (Around sixty-five years or older). This disease is a type of dementia, a chronic disorder that affects a person’s mental processes by a brain injury or age which can lead to memory degeneration, change in one’s personality and problems when it comes to logical reasoning. Alzheimer’s is characterized from being a “progressive, degenerative, and irreversible condition” according to Martina Zimmermann, of the hippocampus (part of the brain associated with memory) and cerebral cortex (part of the brain associated with thoughts and mobility) harbor our ability to memorize and abstractly reason (Zimmermann 2017).
There are three main causes related to suffering from this disease, which are according to Martina Zimmermann “accelerated aging and degeneration of the brain; environmental factors; and physiologic changes based on genetic, metabolic, vascular, and immune system responses.” One supported theory given by researchers is “amyloid cascade hypothesis” (Armstrong 2014; Dorszewska et al. 2016). Which suggests that the accumulation of a peptide called amyloid-beta can lead to the degeneration of amyloidogenic proteins structures while being produced. The misfolding of this proteins generates amyloid beta plaques and tau neurofibrillary tangles which both prevents the communication between neurons, not allowing nerve impulses to pass through the synapse. (Zimmermann 2017)
As said before, one of the most relevant consequences that this disease has is the loss of memory; in addition to that, patients with Alzheimer’s disease can have problems in communications, losing their skills to produce and understand speech, and linked to the loss of control comes the fact that they have problems when recognizing people, even their closest relatives. Being this disease degenerative, according to researchers, there’s a range between five to ten years of life since the disease is diagnosed, getting worse year after year and passing through various stages of the disease (Armstrong 2014; National Institute on Aging 2017; Sheffield 2017)
This disease has no cure, but some researchers have found drugs in order to control the symptoms. There are five approved drugs that can be used to control Alzheimer’s effects in a patient, but all of them have shown that they have a reduced capability of being able to slow the symptoms. Having a series of side effects in some patients, these drugs are named: donepezil, galantamine, memantine, rivastigmine and donepezil and memantine (Sheffield 2017).
In conclusion, the nervous system is one of the most important structures of the human body and it being affected can bring diseases or consequences as well as changes to the persons daily life and can also lead you to death. Multiple Sclerosis, Synesthesia and Alzheimer’s Disease are three of the most common diseases affecting the nervous system, as being the ones discussed through this paper readers got to learn more general information about each of them as was seen a lot of them can be passed through generations. Knowing this, people can prevent or become aware that they have it, in order to start treating it in time. Regular checkups are recommended especially if you know you have a family member with any of this diseases. The nervous system has a lot of functions in our body so one shouldn’t take it for granted and be aware of all of the diseases that can affect it and as a result, can alter ones daily life.