Myelin Sheath 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.

Action potentials can occur more frequently as long there is a continued source of stimulation, as long as the relative refractory period has been reached, which in experiment 2 the refractory period was complete.

Neurons, nerve cells, have three basic parts: the cell body, dendrites, and axon. Neurons transmit signals to other nerve cells and throughout the body. They are simple components in the nervous system. The cell body includes the nucleus, which is the control center of the neuron. The dendrite branches off the cell body and receives information. The axon is attached to the cell body and sends information away from the cell body to other cells. When the axon goes through myelination, the axon part of the neuron becomes covered and insulated with fat cells, myelin sheath. This increases the speed and efficiency of information processing in the nervous system. Synapse are gaps between neurons, this is where connections between the axons and dendrites.

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 &

As well as these there are also the axon of the cell which is covered in myelin sheaths which carried information away from the cell body and hands the action potentials, these are small short bursts of change in the electrical charge of the axon membrane through openings of ion channels, off to the following neurons dendrites through terminal buttons at the end of the axons. Whenever an action potential is passed through these terminal buttons it releases a chemicals that pass on the action potential on to the next neuron through the terminal button and dendrite connection. The chemicals that are

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.

Increasing the extracellular potassium reduces the concentration gradient, and less potassium diffuses out of the neuron and into the cell.

Axons are nerves that connects the brain, spinal cord, muscles, and sensory cells all together

One extension is different from all the others, and is called the axon. Although in some neurons, it is hard to distinguish from the dendrites, in others it is easily distinguished by its length. The purpose of the axon is to transmit an electro-chemical signal to other neurons, sometimes over a

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.

Depolarization in membrane potential triggers an action potential because nearby axonal membranes will be depolarized to values near or above threshold voltage.

Myelin forms around fibers along the axons that are a part of neurons. The Velocity of conducting action potentials can be increased by the myelination process which implies that oligodendrocytes in the central nervous system as well and Schwann cells wrap the axon in myelin. In this process there are layers of glial membrane which an insulator where myelin speeds up action potential conduction. Another way to look at Myelination is that it increases membrane resistance. When the membrane resistance increases this means depolarizing current cannot navigate through the membrane and goes through the low resistance interior. We learned that Node of Ranvier are gaps within the myelin axon which are crucial in producing currents and exchanging

Multiple Sclerosis (MS), is an autoimmune disease in which the surrounding protective coating layer of the axon, myelin, is degraded, resulting in the formation of inflamed lesions (also referred to as plaques) around the regions of the brain and spinal cord. The myelin sheath is not only a protective layer, but it also increases the speed of electrical impulses transfer across the body via saltatory conduction. Depending on the severity of damage to the myelin, it can slow down or distort messages travelling along nerve fibres, some signals may not pass through at all, as damage may eventually degrade and impair the axon itself. This attack is carried out by cytotoxic T cells (CD8+) , which are activated by tip-dendritic cells. It has been observed in case studies where in the presence of increased concentration of CD8+, there is a positive correlation to the increased damage brought to the myelin. However, there are alternative studies that imply that because the myelin presenting peptide CD4+ is involved in the onset of inflammation, the CD8+ may be the one attempting to prevent the attack on the myelin. Still no one is sure of the cause, or is fully aware of the true functions of the receptors involved.

A typical neurone consists of the cell body (soma) which houses the nucleus, the axons, and the dendrites. The nucleus contains all the DNA or genetic material for the cell. The dendrites and axons extend from the cell body. The dendrites receive signals from other cells and bring them to the cell body, whilst the axons carry signals away from the cell body to other cells. The axon can be up to a meter long and is protected by the nerve sheath. This consists of a thick, fatty, inner layer of glial cells which is called the myelin sheath. The outer layer is called the neurilemma and is made from connective tissue. The myelin sheath is interrupted at intervals which causes the neurilemmas to dip down and creates notches. These notches are called

The electrical event that projects the signal along these distances is known as an action potential. The action potential runs from the axon hillock to the end of the axon where more synaptic contacts are made. Target cells of neurons include nerve cells in your brain, spinal cord, cells of your muscles and various glands.