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Myelin Sheath: The lipid-rich sheath surrounding Axons in both the central and peripheral nervous systems. The myelin sheath is an electrical insulator and allows faster and more energetically efficient conduction of impulses. The sheath is formed by the cell membranes of glial cells (Schwann cells in the peripheral and Oligodendroglia in the central nervous system). Deterioration of the sheath in Demyelinating diseases is a serious clinical problem.

Glial Cells

JoVE 10843

Glial cells are one of the two main types of cells in the nervous system. Glia cells comprise astrocytes, oligodendrocytes, microglia, and ependymal cells in the central nervous system, and satellite and Schwann cells in the peripheral nervous system. These cells do not communicate via electrical signals like neurons do, but they contribute to virtually every other aspect of nervous system function. In humans, the number of glial cells is roughly equal to the number of neurons in the brain. Glia in the central nervous system (CNS) include astrocytes, oligodendrocytes, microglia, and ependymal cells. Astrocytes are the most abundant type of glial cell and are found in organized, non-overlapping patterns throughout the brain, where they closely associate with neurons and capillaries. Astrocytes play numerous roles in brain function, including regulating blood flow and metabolic processes, synaptic ion and pH homeostasis, and blood-brain barrier maintenance. Another specialized glial cell, the oligodendrocyte, forms the myelin sheath that surrounds neuronal axons in the CNS. Oligodendrocytes extend long cellular processes that wrap around axons multiple times to form this coating. Myelin sheath is required for proper conduction of neuronal signaling and greatly increases the speed at which these messages travel. Microglia—known as the macrop

 Core: Nervous System

Neuron Structure

JoVE 10842

Neurons are the main type of cell in the nervous system that generate and transmit electrochemical signals. They primarily communicate with each other using neurotransmitters at specific junctions called synapses. Neurons come in many shapes that often relate to their function, but most share three main structures: an axon and dendrites that extend out from a cell body.

The neuronal cell body—the soma— houses the nucleus and organelles vital to cellular function. Extending from the cell body are thin structures that are specialized for receiving and sending signals. Dendrites typically receive signals while the axon passes on the signals to other cells, such as other neurons or muscle cells. The point at which a neuron makes a connection to another cell is called a synapse. Neurons receive inputs primarily at postsynaptic terminals, which are frequently located on spines—small bumps protruding from the dendrites. These specialized structures contain receptors for neurotransmitters and other chemical signals. Dendrites are often highly branched, allowing some neurons to receive tens of thousands of inputs. Neurons most commonly receive signals at their dendrites, but they can also have synapses in other areas, such as the cell body. The signal received at the synapses travels down the dendrite to the soma, where the cell can proce

 Core: Nervous System

Action Potentials

JoVE 10844

Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information in the nervous system. An action potential is a specific “all-or-none” change in membrane potential that results in a rapid spike in voltage.

Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive signals—for instance, from neurotransmitters or sensory stimuli—their membrane potential can hyperpolarize (become more negative) or depolarize (become more positive), depending on the nature of the stimulus. If the membrane becomes depolarized to a specific threshold potential, voltage-gated sodium (Na+) channels open in response. Na+ has a higher concentration outside of the cell as compared to the inside, so it rushes in when the channels open, moving down its electrochemical gradient. As positive charge flows in, the membrane potential becomes even more depolarized, in turn opening more channels. As a result, the membrane potential quickly rises to a peak of around +40 mV. At the peak of the action potential, several factors drive the potential back down. The influx of Na+ slows because the Na+ channels start to inactiv

 Core: Nervous System

Implementation of a Coherent Anti-Stokes Raman Scattering (CARS) System on a Ti:Sapphire and OPO Laser Based Standard Laser Scanning Microscope

1INSERM U1051, Institut des Neurosciences de Montpellier (INM), Université de Montpellier, 2Université de Nîmes, 3CNRS, IES, UMR 5214, 4Aix-Marseille Université, CNRS, École Centrale Marseille, Institut Fresnel, UMR 7249, 5Montpellier RIO Imaging (MRI)

JoVE 54262

 Biology

Whole-mount Confocal Microscopy for Adult Ear Skin: A Model System to Study Neuro-vascular Branching Morphogenesis and Immune Cell Distribution

1Laboratory of Stem Cell and Neuro-Vascular Biology, Genetics and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, 2Earle A. Chiles Research Institute, Robert W. Franz Cancer Center, Providence Portland Medical Center

JoVE 57406

 Developmental Biology

Establishment of a Valuable Mimic of Alzheimer's Disease in Rat Animal Model by Intracerebroventricular Injection of Composited Amyloid Beta Protein

1Institute of Traditional Chinese Medicine, Chengde Medical College, 2Shijiazhuang Obstetrics and Gynecology Hospital, 3Hebei Province Key Research Office of Traditional Chinese Medicine Against Dementia, 4Hebei Province Key Laboratory of Traditional Chinese Medicine Research and Development, 5Institute of Basic Medical Research of Basic Medical School

JoVE 56157

 Behavior

Transplantation of Olfactory Ensheathing Cells to Evaluate Functional Recovery after Peripheral Nerve Injury

1UPRES EA3830, Institute for Research and Innovation in Biomedicine, University of Rouen, 2Neuroscience, Karolinska Institutet, 3Otorhinolaryngology, Head and Neck Surgery Department, Rouen University Hospital, 4Otorhinolaryngology, Head and Neck Surgery Department, Amiens University Hospital

JoVE 50590

 Neuroscience
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