Where is neurons tissue found

Glial cells , or glia or neuroglia , are much smaller than neurons and play a supporting role for nervous tissue. Glial cells maintain the extracellular environment around neurons, improve signal conduction in neurons and protect them from pathogens. Ongoing research also suggests that glial cell number matches neuron number and that they even can send signals themselves. Neurons are nucleated cells with specialized structural properties.

Some neurons have a single long extension axon that reaches great distances, others are very small, star shaped cells without obvious axons See Figure Though neuron shapes vary greatly, every neuron houses its nucleus in a region known as the cell body also called soma from which cellular activity like repair or cell membrane recycling is controlled. Neurons produce many proteins either for their cell membranes or for use when communicating with other cells and therefore also have many rough endoplasmic reticula that are visible with the light microscope; these rough ER are called Nissl bodies.

In figure These short projections are dendrites which receive most of the input from other neurons or stimuli in the extracellular environment; the location of the dendrites on the neuron marks the receptive region of the neuron. Dendrites are usually highly branched processes, providing locations for other neurons to communicate with the neuron. Neurons have polarity—meaning that information flows in one direction through the neuron.

In the Figure The first section of the axon where an action potential is generated is called the initial segment. Often axons are wrapped by myelin sheaths, leaving exposed sections node of Ranvier between segments of myelin. Myelin is produced by oligodendrocytes glial cells in the CNS and acts as electrical insulation, speeding information conduction down the neuron. Once information reaches the terminal end of this neuron, it is transferred to another cell.

The site of communication between a neuron and its target cell is called a synapse. The terminal end has several branches, each with a synaptic end bulb to store chemicals needed for communication with the next cell. Figure Visit this site to learn about how nervous tissue is composed of neurons and glial cells. Neurons are dynamic cells with the ability to make a vast number of connections, to respond incredibly quickly to stimuli, and to initiate movements on the basis of those stimuli.

They are the focus of intense research because failures in physiology can lead to devastating illnesses. Why are neurons only found in animals? There are trillions of neurons in the nervous system and cell shape can vary widely. Three common shapes of neurons are shown in Figure Multipolar neurons have multiple processes emerging from their cell bodies hence their name, multipolar.

They have dendrites attached to their cell bodies and often, one long axon. Motor neurons are multipolar neurons, as are most of the CNS.

Bipolar cells have two processes, which extend from each end of the cell body, opposite to each other. One is the axon and one the dendrite. Bipolar cells are not very common. They are found mainly in the olfactory epithelium where smell stimuli are sensed , and as part of the retina in the eye. Unipolar cells have one long axon emerging from the cell body, but the cell body is located at neither end of that axon. At one end of the axon are dendrites, and at the other end, the axon forms synaptic connections with a target cell.

Unipolar cells are exclusively sensory neurons and have their dendrites in the periphery where they detect stimuli. There are six types of glial cells. Table Astrocytes have many processes extending from their main cell body not axons or dendrites like neurons, just cell extensions.

Those processes extend to interact with neurons, blood vessels, or the connective tissue covering the CNS Figure Generally, they are supporting cells for the neurons in the central nervous system. Some ways in which they support neurons in the central nervous system are by maintaining the concentration of chemicals in the extracellular space, removing excess signaling molecules, reacting to tissue damage, and contributing to the blood-brain barrier BBB.

The blood-brain barrier is a physiological barrier that keeps many substances that circulate in the blood from getting into the central nervous system, restricting what can cross from circulating blood into the CNS. Usually, blood vessels are leaky because there are gaps between the cells of the vessel walls. These gaps permit rapid movement of molecules out of the blood into the extracellular space around tissue cells, delivering nutrients and hormones.

However, the neurons of the brain may be affected by rapid, regular changes in extracellular concentrations preventing signal transmission. To prevent such fluctuations, astrocytes release compounds to the blood vessels, inducing tight junctions between the otherwise leaky blood vessel cells.

When the BBB is intact, nutrient molecules, such as glucose or amino acids, must now pass through the vessel cells of the BBB by transcellular processes using membrane proteins. The cell body is like a factory for the neuron. It produces all the proteins and contains specialized organelles such as nucleus, granules and Nissl bodies.

Neuron : This image illustrates the parts of a neuron. The dendrites receive incoming signals while axons propagate signals away from the neuron cell body. The myelin sheath surrounds and insulates the axon. The axon is surrounded by a whitish, fatty layer called the myelin sheath. Outside the myelin sheath there is a cellular layer called the neurilemma.

In the peripheral nervous system, Schwann cells are neuroglia cells that support neuronal function by increasing the speed of impulse propagation. The Schwann cells are underlain by the medullary sheath.

The medullary sheath is interrupted at intervals by the nodes of Ranvier. Illustration of the Schwann Cells and the Myelin Sheath : Transmission electron micrograph of a myelinated axon. The myelin layer concentric surrounds the axon of a neuron, showing Schwann cells. The nervous system consists of nervous tissue, which is composed of two principal types of cells called neuron and neuroglia. Nervous tissue, one of the four main tissue types, is composed of neurons and supporting cells called neuroglia.

There are six types of neuroglia—four in the central nervous system and two in the PNS. These glial cells are involved in many specialized functions apart from support of the neurons. Neuroglia in the CNS include astrocytes, microglial cells, ependymal cells and oligodendrocytes. In the PNS, satellite cells and Schwann cells are the two kinds of neuroglia. Astrocytes are shaped like a star and are the most abundant glial cell in the CNS. They have many radiating processes which help in clinging to the neurons and capillaries.

They support and brace the neurons and anchor them to the nutrient supply lines. They also help in the guiding the migration of young neurons. Astrocytes control the chemical environment around the neurons.

Microglial cells are small and ovoid un shape with thorny processes. They are found in the CNS. A smear means that a small chunk of nerve tissue from the spinal cord or brain was literally squashed and spread out on a slide. That's the only way to see neurons, because they have many extensions that would be cut off in a typical section.

Nervous tissue X Motor Neuron smear. Each neuron n has extensions called processes axons and dendrites that allow it to communicate with other neurons. The pink lines that are attached to these neurons are their processes. You can see that they are much smaller than neurons.