A Look at Myelin and Myelin-Related Disorders Essay

6.The fatty substances produced by certain glial cells that coat the axons of neurons to insulate, protect, and speed up the neural impulse is the myelin.

Multiple Sclerosis (MS) is a neurologic disease that affects the Central Nervous System (CNS) through cellular immune response and the demyelination of CNS white matter (McCance et al., 2014, pp. 630–633). The initial causes of MS are unknown however, it is believed that it could possibly be due to an immune response to an initiating infection or an autoimmune response to CNS antigens on the myelin itself (Brück, 2005) (Miljković and Spasojević, 2013). MS is a result of the degradation of the myelin sheath surrounding neurons and therefore disrupts the transmission of action potentials along these cells. MS can display itself in the form of symptoms ranging from muscle weakness to trouble with sensation and coordination (NHS, 2016). The degradation of myelin leads the body to attempt to remyelinate the neurons, a process that in turn leads to the thickening of the cell by glial cells and this causes lesions to form (Chari, 2007). It is this thickening (sclerae) from which the disease gets its name. Sufferers of MS can either have a relapsing type of MS, in which there are episodes that lead to the worsening of symptoms for a period of time, or a progressive type of MS where symptoms gradually progress and worsen (McCance et al., 2014, pp. 630–633).

The central nervous system (CNS) comprises grey matter, which contains neuron cell bodies and white matter, which contains the nerve axons. Most of the nerve axons are concentrically wrapped around by lipid-rich biological membrane, known as the myelin sheath. In the CNS, myelin is produced by oligodendrocyte. a type of glial cell. (Pfeiffer et al., 1993). These electrical insulating, multilamellar membranes significantly increase the electrical resistance, in which to prevent leakage of electrical currents from the axons, as well as decrease electrical capacitance to reduce the ability of the axons to store electrical energy (Shivane &

7. Myelin Sheath whitish fatty segmented sheath around most long axons. It protects the axon, electrically insulates fibers from one another , and increases the speed of nerve impulse transmition.

The breakdown of the myelin sheath is caused from a mutation of the gene that makes the Adrenoleukodystrophy protein (ALDP). This ALD protein helps the body metabolize saturated very-long-chain fatty acids found in the serum and tissues of the central nervous system. The newly mutated gene no longer acts as a help aid to breaking down the long-chain fats. Therefore, the body starts accumulating an abnormal amount of fat in the nervous system, adrenal gland and testes that sets off an unusual response in the immune system; demyelination.

Multiple Sclerosis is a disease that attacks the myelin coating over the nerve receptors in your brain and spinal cord. Myelin is a fatty material that coats and protects the nerves in your brain. These nerves send signals to the rest of your body enabling

Myelin, the common factor in each disease, is a subsatnce that surrounds and insulates axons on some nerve cells, allowing for a faster transporting of signals and proper functioning of the nervous system. A demyelinating disease results in the damage of nerve fibers in the brain and spinal cord due to the myelin sheath being destroyed, which is life threatening.

“Multiple sclerosis (MS) is a disease in which your immune system attacks the protective sheath (myelin) that covers your nerves” (Mayo Clinic). The immune system is a defensive system that protects your body from diseases and illnesses such as parasites and bacteria (Science Museum). Not only does your immune system defend the human body but also the immune system can work against the body, which is known as autoimmune disease. Since the immune system is working against your body to attack the myelin, this creates an opportunity for multiple sclerosis to invade the nerves in the central nervous system (CNS). The myelin within the body acts like insulation to protect and coat the nervous system (National Multiple Sclerosis Society). Once the myelin is eroded, the nerves become exposed which then causes signals to and from the brain to become distorted or irrupted causing a wide range of symptoms to occur (National Multiple Sclerosis Society). The effect of the myelin eroding is an irreversible process (Mayo Clinic). “The damaged myelin forms scar tissue (sclerosis), which

Multiple sclerosis is characterized by inflammation, demyelination, and axonal damage in the brain and spinal cord with a loss of myelin that covers the axons. As the myelin sheath regenerates, scar tissue forms, which looks like plaques on magnetic resonance imaging scans. Multiple sclerosis arises when immune-mediated inflammation activates T cells and causes the T cells and immune mediators to cross the blood-brain barriers into the CNS and attack oligodendrocytes (ie, a type of neuroglial cell with dendritic projections that coil around axons of neural cells). When the oligodendrocytes are attacked, the myelin sheath is replaced by scar tissue, which forms throughout the CNS. As a result of damage to the myelin sheath, the ability to transmit and conduct nerve impulses along the spinal cord and in the brain is interrupted, leading to muscle weakness, fatigue, loss of coordination, balance impairment, and cognitive and visual disturbance (DeLuca & Nocentini, 2011). This disease is characterized by unpredictable remissions that occur over several years. During periods of remission, the myelin sheath usually regenerates and symptoms may resolve, but the myelin cannot be completely repaired. As the disease progresses, the myelin sheath is destroyed and nerve impulses become much slower or absent and symptoms worsen. When degeneration exceeds self-repair ability, permanent disability results. There are four defined clinical types of

By attacking the myelin MS causes inflammation and damage to the myelin itself (MS Society of Canada, 2016). Myelin is the main source of transportation for nerve impulses; this is done through the nerve fibres that are protected by the myelin (MS Society of Canada, 2016). If the myelin is only slightly damaged the nerve impulses can continue with a few minor interruptions, but if the damage is extensive then problems become more apparent (MS Society of Canada, 2016).

Multiple Sclerosis is an inflammatory demyelinating neurodegenerative disorder of the central nervous system that has the potential to cause significant disability in those affected through the body's immune system attacking and destroying the myelin sheaths surrounding the axons. Myelin is rich in lipids and proteins that form layers around the nerve fibers and acts as insulation and protection. This damage to the myelin in the CNS, and to the actual nerve fibers, has the potential to block the transmission of nerve signals between the brain and spinal cord and also other parts of the body. This disruption of the nerve signals produces the primary symptoms of MS which then possibly lead to secondary and tertiary symptoms stemming from these

Multiple Sclerosis is an autoimmune disorder where the myelin sheath within the Central Nervous System is attacked (National Multiple Sclerosis Society, 2017). The myelin sheath protects the axon of the nerve cell. When the myelin sheath is intact, the axon is able to carry impulses away from the neuron’s cell body, and the message carried is clear. With Multiple Sclerosis, the myelin sheath becomes scarred, hence the word “sclerosis”, and distorts the nerve impulses traveling over the CNS (National Multiple Sclerosis Society, 2017). This may cause the message to be changed or stopped altogether.

These neurons are vital for passing information from the brain to the body through the CNS. The neuron is made up of the body and axon which is broken into two parts: myelin sheath and axon terminals. Multiple sclerosis takes the immune system and attacks the myelin sheath causing it to deteriorate. As the myelin sheath is damaged it leaves permanent neurological damage and the electrical impulses that travel through the myelin sheath are blocked or disrupted (Compston, Coles 2008). As the CNS deteriorates the body becomes dysfunctional and the individual cannot perform their activities of daily living. Now that the CNS is disrupted or unable to communicate with PNS, this can lead to numerous signs and symptoms because the PNS is failing to receive electrical impulses.

To improve the speed of their communication, and to keep their electrical charges from shorting out with other neurons, axons are often surrounded by a myelin sheath. The myelin sheathmyelin sheathA layer of fatty tissue surrounding the axon of a neuron that acts as an insulator and allows faster transmission of the electrical signal. is a layer of fatty tissue surrounding the axon of a neuron that both acts as an insulator and allows faster transmission of the electrical signal. Axons branch out toward their ends, and at the tip of each branch is a terminal button.

Glial cells are the most numerous cells in the brain, outnumbering neurons nearly 3:1, although smaller and some lacking axonal and dendritic projections. Once thought to play a subpar role to neurons, glial cells are now recognized as responsible for much greater functions. There are many types of glial cells, including: oligodendrocytes, microglia, and astrocytes. Oligodendrocytes form the myelin sheath in the CNS, by wrapping themselves around the axons of neurons. Their PNS counterpart, Schwann cells, are also considered glial cells. This sheath insulates the axon and increases the speed of transmission, analogous to the coating on electrical wires. Microglia are considered to be “immune system-like”; removing viruses, fungi, and other wastes that are present. Astrocytes, however, are considered to be the most prominent. Their functions span throughout the brain, including, but not limited to: the synchronization of axonal transmission via G-protein-coupled receptors, blood flow regulation via the dilation of blood vessels, and the performance of reactive gliosis in conjunction with microglia. Both astrocytes and oligodendrocytes develop from neuroepithelial cells. Other types of glial cells include Radial glia, which direct immature neuron migration during development.