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According to Kleiner (2005), the brain tissue is made up of glial cells and neurons. The former makes up 90 percent of the tissue. Neurons, which are also referred to as nerve cells, are responsible for the conduction of signals from the brain to the rest of the body. Glial cells, on the other hand, do not transmit nerve signals.
On the contrary, they serve such other physical and nutritional functions as the digestion of dead neurons and the provision of neuronal support. They are also involved in the manufacture of the myelin sheath (Pinel, 2011). In this lecture, the presenter will analyze the growth and degeneration of brain cells.
To this end, the presenter will examine what facilitates the growth process, what happens when the brain cells die, as well as the impacts of the growth and degeneration of brain cells on the brain and on human functioning. The presenter will provide an example of a disorder brought about by disturbances in the growth of brain cells, as well as an example of a disorder brought about the degeneration of brain cells.
The Growth and Degeneration of Brain Cells
The growth of new brain cells depends on various factors. One of them is the activity of the protein responsible for altering epigenetic marks in the cell’s genetic material (Stannard, 2009). Another factor that enhances the growth of brain cells is exercise. According to Jason & Greenamyre (2011), exercise not only improves general health, but also enhances the growth of new brain cells.
It also stimulates the growth of neurons in the hippocampus, especially the dentate gyrus. The gyrus is responsible for neurogenesis. Meditation also facilitates the growth of brain cells. The relationship between meditation and growth of brain cell is complex. Several studies have shown that the growth of brain cells is accelerated among people who meditate, compared to those who do not engage in this activity (Stannard, 2009).
The use of antidepressant drugs is also known to accelerate the growth of brain cells. According to Kleiner (2005), depression, anxiety, and stress are known to cause the death of brain cells. The trend is, however, reversed by the use of antidepressants, such as Prozac. The drugs facilitate neurogenesis (Kleiner, 2005).
Environmental factors affect the growth of brain cells. When the brain is exposed to an enriched environment, there is increased growth of neurons in the hippocampus than when it is exposed to an impoverished environment. Research has also proven that learning enhances the growth of neurons.
The neurons can die in the absence of learning. Regulating the intake of calories is another factor affecting the growth of brain cells. The regulation protects the neurons, thus enhancing the growth of the cells.
What Happens when Brain Cells Die?
The cells die through a process referred to as apoptosis. Cells that are dying shrink, condense, and finally fragment, releasing apoptotic bodies. The released bodies are small and bound by a membrane. They are phagocytosed by other cells (Orrenius et al., 2010). The phargocytosis process involves several cells. They include neutrophils, macrophages, dendritic cells, and B lymphocytes.
The process begins when a neutrophil or microphage engulfs the dead cell in a phagocytic vesicle. The vesicle is also referred to as a phagosome. The next step in the death of brain cells involves the fusion of the phagosome with a lysosome. The combination of the two gives rise to a phagolysosome. The contents of the lysosome destroy the cell engulfed in the phagosome.
Having looked at the process through which brain cells die, it is now important to look at what happens when this happens. In other words, what are some of the effects associated with the death of brain cells in humans and other animals? According to Sciencemuseum.org.uk (2013), one of the most obvious effects associated with the death of brain cells is the development of diseases associated with the brain.
The diseases impair the functionality of the brain, affecting the memory and cognitive ability of the individual. One such common disease associated with the death of brain cells is Alzheimer. The condition is associated with dementia and such other impairments of the brain.
According to Sciencemuseum.org.uk (2013), the death of brain cells is also associated with the formation of ‘plaques’ by some proteins in the body. The plaques interfere with the functioning of the cells. The impairment leads to the death of more brain cells. The figure below is an illustration of an Alzheimer’s brain affected by plaques:
Figure 1: Confocal Image of an Alzheimer’s Brain Affected by Amyloid Plaque
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Source: Sciencemuseum.org.uk (2013)
Another form of protein in the brain creates what Sciencemuseum.org.uk (2013) refers to as ‘tangles’. The tangles interfere with the structure of the affected brain cells, which consequently affects their functionality. The effect is the death of more brain cells. The transmission of signals from one neuron to the other is performed by, among others, chemicals specializing in this function.
The chemicals decline when the brain is inflicted by such diseases as Alzheimer. What this means is that the function of the brain is interfered with. Some of the conditions brought about by the death of brain cells are irreversible. For example, Sciencemuseum.org.uk (2013) opines that majority of dementias cannot be reversed.
Many researchers are engaged in efforts to find cures for these conditions. In the meantime, there are drugs aimed at alleviating some of the symptoms associated with conditions brought about by the death of brain cells.
The Impacts of the Growth and Degeneration of Brain Cells
The growth and degeneration of brain cells have various impacts on the brain and on human functioning. It affects the physical and mental functioning of the human. There are several disorders arising from neuro-degeneration. They include Alzheimer’s disease, Parkinsonism, multiple sclerosis, and Huntington’s disease (Jason & Greenamyre, 2011).
The degeneration of brain cells involves the death of nerves and loss of brain tissue. As a result, the size of the brain reduces significantly. The reduction in the size of brain impairs the functioning of this organ severely (Stannard, 2009). The impairment is transferred to other parts of the body.
Degeneration of brain cells affects various parts of the brain. One such part is the hippocampus. The hippocampus is regarded as center of memory creation. When cells in this part of the brain degenerate, they impair the memory of the individual. Another part of the brain affected by degeneration is the cortex.
The cortex shrivels as a result of neurodegeneration. The shrinking impairs thinking capabilities, planning, and remembering. The center is responsible for movement, sensory stimulation, emotion, higher intellectual functioning, and speech. The ventricles are also affected by the degeneration of brain cells. The ventricles are fluid-filled spaces that resemble indents.
The spaces occur naturally in the brain. When the brain starts to degenerate, the ventricles grow larger. The increased size of these centers takes up the space occupied by the brain. As a result, the enlarged spaces reduce the size of the brain.
The growth of brain cells has various positive impacts. The growth is associated with reduced levels of anxiety and depression. The reason for this is that the newly generated cells are found in the hippocampus. It is the part of the brain associated with learning, memory, anxiety, and depression (Kleiner, 2005)
An Example of a Disorder Caused by Disturbances
There are various disorders associated with disturbances in the growth of brain cells. One such disorder involves the growth of brain tumors. The tumor is a collection of cells growing independent of other parts of the body (Orrenius et al., 2010). One such tumor is the meningiomas. The tumor grows between the meninges.
Another is the infiltrating tumor, which grows in a diffused manner through the surrounding tissues. Brain tumors are characterized by headaches, which are usually severe in the mornings. They are also associated with nausea and vomiting, change in speech, vision, or hearing. Other issues include problems with balancing and mood changes.
An Example of a Disorder Caused by Degeneration
An example of a neurodegerative condition is the Parkinson’s disease (Pinel, 2011). It is a movement disorder characterized by stiffness or tremor of the fingers. The condition becomes more severe with time. In advanced stages, the patient experiences resting tremors. The tremors are, however, not experienced in voluntary activities and sleep.
Muscle rigidity, difficulty to initiate movement, slow movement, mask-like facial expressions, pain, and depression are also symptoms associated with this condition. The disease is brought about by neurodegeneration of the substantia nigra. The degeneration leads to reduced production of dopamine.
Jason, R., & Greenamyre, J. (2011). Toxicological sciences. London: McGraw-Hill.
Kleiner, K. (2005). Marijuana might cause new cell growth in the brain. New Scientist, 8(7), 2-4.
Orrenius, S., Nicotera, P., & Zhivotovsky, B. (2010). Cell death mechanisms and their implications in toxicology, Alzheimer’s Research & Therapy, 5(4), 34-38.
Pinel, J. (2011). Biopsychology. London: Pearson.
Stannard, S. (2009). Comparing a healthy brain to an Alzheimer’s brain. Genome Biology, 3(5), 4-9.