The myelin sheath may not seem to be too important in the overall grand scheme of the central nervous system. However, I personally know what damage to this thin layer of protein and fat can cause in a human being. In 1996, two years before I was born, my maternal grandmother was diagnosed with chronic progressive multiple sclerosis. She first noticed that something was awry in 1994. Her leg began to flop when she walked, she had blurred vision, and had very limited strength in her hands. After numerous spinal taps and testing, she was diagnosed after a Magnetic Resonance Imaging (MRI) scan. MRIs are able to image soft tissue very well and are therefore used to see the structure of the brain. The imaging capabilities are expanded when considering the superior spatial resolution. This spacial resolution allows the doctor to see brain details down to the millimeter. All these features were crucial in observing the brain lesions in my grandmother’s brain which ultimately led to her diagnosis. Brain lesions are an area of brain tissue that has been damaged. Brain lesions can be compared to scar tissue except instead of being on the skin, they are located in the brain. Multiple sclerosis has been proven to have a direct correlation to brain lesions.
Multiple sclerosis is an autoimmune disease that results from the immune system attacking the myelin sheath that encapsulates the axons of neurons in the brain and spinal cord. The myelin sheath assists in spreading nerve impulses from the soma, or the cell body, to the terminal branches of the axon. The anatomy can be seen in Figure 1. The myelin sheath also insulates and protects the axon and allows the messages through the neurons to speed up. In the case of multiple sclerosis, the body’s immune system attacks the central nervous system and targets the myelin sheath directly. Also, oligodendrocyctes, the cells that make myelin, are damaged and killed. The amount of damage is indirectly related to the consistency of the signal getting through. That is, the more damage that is inflicted on the myelin sheath, the more damage there is to the axon, and less of the initial signal gets through. This is due to the nature of an action potential. The action potential is a quick charge that travels down the axon. The action potential is created by the movement of charged ions in and out of channels in the axon’s membrane. Therefore, if less charged ions are able to get through to the axon’s membrane, there will not be enough voltage to cause an action potential. A graphical and pictorial representation can be seen in Figure 2. Reaching threshold is required in order for the neuron to fire. Any amount below threshold will not be able to cause the neuron to fire. This progression of less and less action potentials was seen in my grandmother. My grandmother went from completely healthy to not being able to do anything. Her neurons were so badly damaged that she could not voluntarily move any part of her body after only a handful of years. Ultimately, she passed away from the complications of multiple sclerosis in December 2001. From her, I grew up knowing the complications of multiple sclerosis. However, this assignment allowed me to understand more about the disease in connection to the nervous system. I also learned about how the disease progressed and how she was diagnosed by getting information from my mother. Overall, this tiny myelin sheath can have major complications if it is damaged. The myelin sheath has much more importance in the grand scheme of the body as proven by multiple sclerosis.
Works Cited
Immune-Mediated Disease. (n.d.). Retrieved from https://www.nationalmssociety.org/What-is-MS/Definition-of-MS/Immune-mediated-disease