Compact Myelin Essay

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 &

Lightly myelinated Aδ fibers and unmyelinated C fibers have thinner axons and a higher threshold of activation. Nociceptors of Aδ fibers can be either mechanosensitive or thermosensitive. Polymodal nociceptors (of C fibers), may respond to both mechanical and thermal stimuli, as well as chemicals [261-263]. When nociceptors are activated, the fibers transmit action potentials along the axon to the spinal cord [264, 265]. The spinal cord mediates sensory and motor communication between the periphery and the brain, and is organized into four regions; cervical, thoracic, lumbar, and sacral. The gray matter contains cell bodies of neurons and glia and is divided into the dorsal horn, intermediate column, lateral horn, and ventral horn. The dorsal horn is comprised of sensory nuclei that receive and process incoming sensory information [266], and like the rest of the spinal gray matter, is organized histologically into parallel laminae based on the size and density of neurons [267]. In general, laminae I to IV are involved in exteroceptive sensation whereas laminae V and VI are involved in proprioceptive sensations [263]. Nociceptors terminate in the dorsal horn laminae in a

This was determined through a set of experiments. To determine if sodium channel clustering depended on glial cells, hippocampal cells were cultured in the absence of glial cells. This experiment showed that, in the absence of glial cells, Na+ channels were found along the entire length of the axon. They were not concentrated in clusters. Then, another experiment was conducted to determine if the node of Ranvier formation was contact dependent. In this experiment, the dorsal root ganglia were bathed in the extracellular fluid of Schwann cells. Again, nodes of Ranvier did not form. This showed that the node of Ranvier formation mechanism was contact dependent. Another experiment was done to determine if node of Ranvier formation depended on molecular signaling between the Schwann cells and the axon. In this experiment, Schwann cells on a myelinated axon were killed. The nodes of Ranvier disappeared. This showed that molecular signaling played a role in node of Ranvier formation. Eventually, an experiment found that ankyrin G was concentrated at nodes of Ranvier. To determine what proteins interacted with

Areas of high neuroplasticity also tend to be areas of scarce myelination. As mentioned earlier in this paper, these areas both tend to reside within the evolutionarily new neocortex. Neocortical areas exhibit an early and brief myelination cycle as compared to older and deeper brain areas, which exhibit later and extensive myelination. The axons of the neocortex are long, thin, and sparingly myelinated compared to other regions of the brain, as observed through Nissl staining. These Nissl stains verify a pattern of myelination in which the highest cortical areas are the most sparsely myelinated. Perhaps unsurprisingly, the pattern of neural damage, such as neurofibrillary tangles associated with AD, follows the pattern of myelination. In other words, these tangles develop in the areas that are most sparsely myelinated. In contrast, areas of heavy myelination are much more resistant to stressors that cause neuronal degeneration5. It is believed that areas of decreased myelination are characteristic of cells retained in their juvenile state. Without the structural encasing of myelin, these cells are more flexible to changes, and thus have higher plasticity than cells that are heavily myelinated. Therefore, neurons of the neocortex are likely highly plastic largely because of their lower degree of myelination.

Myelin is produced by oligodendrocytes in the Central Nervous System and by Schwann cells in the Peripheral Nervous System.2 Oligodendrocytes (and Schwann Cells) are types of cells known as glial cells.2

Myelin are important parts of the nervous system, they are “capable of responding to experiences for learning and long-term behavioral capacity” (Myelinate). The article goes into depth about the different experiments that have gone on. For example, McKenzie et al. had done an experiment with adult mice to determine if there was a difference in mice that grew new oligodendrocytes. The article also went into great detail about different disorders caused by damaged or malfunctioned myelin. Myelin is truly important for our brains as it surrounds axon of some nerve cells and forming an insulating layer. On the other hand, myelin is an outgrowth of the glial cell, which is also an important part of the nervous system. (122)

Formalin- prepared optic nerves (ON) was mainly used as the materials and sources of information in the study. To identify the human ON areas where demyelination has occurred, Jennings and Caroll used luxol fast blue (LFB) and hamatoxylin and eosin. Cat ON, on the other hand, were stained with toluidine to distinguish the myelin sheaths in preparation for electron microscopy processing. After this, immunohistochemistry was effectually conducted in order to differentially mark the neuroglia. The digital images formed were then examined and evaluated to quantify the data. Results revealed the presence of oligodendroglial cells in MSON lesions, which further confirms the link between remyelination as a result or consequence of

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.

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.

My neuron was made of red acetate, because I wanted a material that can be managed and cut it, without great difficulty. First, on a piece of Xerox paper, I draw the two main parts of the neuron. Next, I traced my pictures on the acetate with a permanent marker to outline them. After that, I used a coffee stirrer to put together the soma and the axon. For the nucleus, I utilized a pink bead. In addition, I wrapped the axon with clear tape to represent the myelin sheath. Finally, I added the dendrites and axon terminals, which were made of black yarn. I carefully attached these elements with a hot glue gun. I made several mistakes and I have to try several times, until I was satisfied.

 Myelination is the formation of fatty substance around the axons of the neurons. This is what helps speed up the electrical pulses therefore speeding up the transmission of the messages and information shared between the pair of neurons.

The function of the sensory neuron is to carry around action potentials from a sense organ or receptor to the central nervous system. The structure of the sensory neuron has the sensory receptors, the structure of these are that they vary however they utilize the gated sodium ion channels which are present in the membrane. The function of these are that they are able to detect a change in the environment and they are able to create an action potential with sodium ions. The schwann cell wraps around the axon and is used to insulate it from the myelin sheath. The cell body is in a ganglion which is close to the CNS. There is also the axon, this is short communication route which is between the cell body and the axon terminals, in this there

Microscopical techniques have been an irreplaceable source of our knowledge about the nervous system. Not only have they provided clear evidence supporting the variety of hypotheses but also deepened our understanding by allowing the researchers to make valid links between the components of the nervous system and their functions. In this paper,

Microscopical techniques have been an irreplaceable source of our knowledge about the nervous system. Not only have they provided clear evidence supporting the variety of hypotheses but also deepened our understanding by allowing the researchers to make valid links between the components of the nervous system and their functions. In this paper,

Neurons are made up of four regions, the cell body, dendrites, axons and presynaptic terminal. The cell body (soma) contains the nucleus of a neuron and the endoplasmic reticulum. Extending out from the cell body are processes called dendrites and axons. These processes conduct nerve impulses. Dendrites conduct impulses toward the cell body while axons conduct impulses away from the cell body. A fatty sheath called myelin sheath encases axons. It is the greatly expanded plasma membrane of an accessory cell called the Schwann cell where the sheath of one Schwann cell meets the next. The axolemma is the portion of the cell membrane surrounding the axon of a neuron and is responsible for maintaining the membrane potential of the neuron. A single neuron, especially one in the central nervous system may have thousands of other neurons synapsing on it. Some of these release activating (depolarizing) neurotransmitters; others release inhibitory (hyperpolarizing) neurotransmitters.