The unit objective I’m covering with my project is how neurons carry an electrical charge. My project is on the nervous system defects of multiple sclerosis. For this project, I made a couple of neurons out of clay, modeling one after a healthy neuron and the other after a neuron afflicted by multiple sclerosis–a disease of the central nervous system.
To carry an electrical message properly through the nerves, neurons have dendrites where the information enters the neuron; a cell body to give structure and store information in the neuron; axons to transport electrical impulses, and myelin–or Schwann cells in the peripheral nervous system–to protect and insulate the axon. Electrical charges are sent from neuron to neuron, bridging the gap (called a synapse) by converting to a chemical signal in the form of neurotransmitters which bind to the other end of the synapse and convert the signal back to an electrical one.
The differences between a neuron in a healthy person and a neuron with multiple sclerosis lie in the myelin sheaths surrounding the axons of the neuron. A healthy neuron has intact Schwann cells or myelin sheaths that serve to protect axons and ensure that action potentials are carried along safely. Multiple sclerosis is an autoimmune and neurodegenerative disorder that occurs when autoreactive cells in the body cross the blood brain barrier and begin to attack the nerves. This causes inflammation of the nerves and glial cells–especially the oligodendrocytes which are responsible for making myelin. With the body’s immune defenses attacking the myelin sheaths, the nerves become exposed and the impulses along the axon are impeded. It is the lack of myelin around the axons that causes electrical charges to be carried, leading to impaired nervous system function. Like how stripping bark off a tree exposes the tree’s insides to damage, removing myelin from a nerve exposes it to damage.
Patients with multiple sclerosis may experience cycles of nerve attacks followed by periods of no symptoms, then more attacks with worsened symptoms. While it is possible to remyelinate the nerves after a multiple sclerosis attack, the myelin usually grows back significantly thinner, and the messages along the axon travel sluggishly. With repeated relapses of multiple sclerosis, oligodendrocytes may be damaged beyond repair and lose the ability to produce myelin. The body can reroute messages by using other undamaged nerves, though if no undamaged nerves remain between the CNS and the desired extremity, the message cannot be rerouted.
Since multiple sclerosis is a disorder affecting the nervous system, it can cause a variety of problems relating to movement and signal relaying in the body. Muscle spasms, tingling, and numbness are all common symptoms of MS. Balance, speech, and gross motor movements are also often experienced by people with MS, and it can get to be as severe as respiratory problems, blood clots, blindness, and paralysis in the later stages. Multiple sclerosis can be a debilitating disease, but there are several drugs to reduce the occurrence of relapses in patients with MS, as well as prevent the formation of lesions in the brain associated with nerve damage. Multiple sclerosis is not a curable disease, however, and the recovery process varies heavily. Many patients experience gradually worsening conditions indefinitely, while others may make a partial or complete recovery between relapses.
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Multiple Sclerosis Trust. (2021, December 1). Nerve cells (neurons). Nerve cells (neurons) | MS Trust. Retrieved November 9, 2022, from https://mstrust.org.uk/a-z/nerve-cells-neurons
Zéphir, H. (2018, April 19). Progress in understanding the pathophysiology of multiple sclerosis. Revue Neurologique. Retrieved November 9, 2022, from https://www.sciencedirect.com/science/article/pii/S0035378717308597