The brain is a complex organ made up of two major cell types known as neurons and glia. Neurons are the nerve cells of the brain; they signal to each other within the brain, and signal to the body to control muscle movement, organ function, emotion and higher mental functions. The glia are a class of cells within the brain designed to support the health and functioning of the neurons. Neurodegenerative disorders occur when abnormalities in the brain lead to a decrease in neuron functioning, either due to genetic or environmental factors, which can lead to a range of debilitating symptoms in the body. A number of generally non-genetic diseases of the brain have been identified that have devastating effects.
Parkinson's Disease
Parkinson's disease is a neurodegenerative disorder that is characterized by a lack of dopamine in the brain. Dopamine is a chemical that is a type of neurotransmitter, that is used for signaling between neurons in the brain. Patients with Parkinson's disease lose the ability to control muscle movement and experience uncontrolled muscle twitching and contractions which can hinder daily life. A 2006 study published in the Journal of Neural Transmission reports that the vast majority of Parkinson's cases are non-genetic, and the risk of developing the disease is influenced by a number of environmental factors.
Exposure to pesticides, a high-fat diet, excess caloric intake and and head trauma all increase the risk of developing Parkinson's. In contrast, drinking coffee and use of non-steroidal anti-inflammatory drugs is thought to decrease risk. Further research will shed more light on the mechanisms and risk factors that cause Parkinson's disease.
Alzheimer's Disease
Alzheimer's disease is typically a non-genetic disorder that leads to progressive neurodegeneration within the brain. In Alzheimer's, the brain accumulates aggregates of toxic proteins which care called amyloid beta plaques. These plaques lead to a breakdown in cellular structure and the formation of neurofibrillary tangles. Both amyloid plaques and neurofibrillary tangles are the hallmarks of Alzheimer's disease. Patients with Alzheimer's disease experience a progressive breakdown in mental function leading to memory loss, a change in personality and behavior and a loss of muscle function.
A number of environmental factors have been identified that affect an individual's risk for developing Alzheimer's. Head trauma, high blood pressure, high cholesterol and exposure to metals such as aluminum and zinc are thought to increase the risk of Alzheimer's, according to the Fisher Center for Alzheimer's. The center also reports that individuals who grew up in the suburbs, attended post-secondary schools and maintained an antioxidant-rich, low-fat diet are at lower risk for developing in the disease.
Sporadic ALS
Amyotrophic lateral sclerosis, or ALS, is a neurodegenerative disorder that leads to degeneration of a subset of neurons known as motor neurons. These cells link the central nervous system to the muscles of the body, so the degeneration of motor neurons leads to a loss of muscle control and eventually, paralysis. Sporadic ALS is a form of the disease that has no genetic component, and instead develops due to acquired changes within the brain and spinal cord.
According to Davidson College, sporadic ALS may be caused by an immune response to nerve injury. Following the injury to one nerve, the immune system over-reacts, leading to damage in neighboring nerves, and a further increase in immune function. As the cycle continues, more and more nerve cells become damaged and die, leading to the symptoms of ALS.
