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Illustration of a Nerve Cell (neuron) The illustration is simplified, and not to scale.
The body is composed of billions and billions of cells of all types, shapes and sizes .The cells of the nervous system (CNS), known as neurons or nerve cells, are specialised to relay messages using an electrochemical process.
The neuron (nerve cell) has a:
- Nucleus -
contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones (alkaline proteins), to form chromosomes (organized structure of DNA and protein). The genes within these chromosomes are the cell's nuclear genome. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulating gene expression — the nucleus is therefore the control centre of the cell. - Cell body -
Soma - The word soma is Greek, meaning "body"; the soma of a neuron is often called the "cell body".the bulbous end of a neuron, containing the cell nucleus. - Dendrites -
branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, of the neuron from which the dendrites project - Axon -
Nerve fibre -A long, slender projection of a nerve cell, or neuron, that conducts the electrochemical impulses away from the neuron's cell body or soma. An axon is one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being dendrites, axons are distinguished from dendrites by several features, including shape (dendrites often taper while axons usually maintain a constant radius), length (dendrites are restricted to a small region around the cell body while axons can be much longer), and function (dendrites usually receive signals while axons usually transmit them). All of these rules have exceptions, however. Some types of neurons have no axon, these are called amacrine cells, and transmit signals from their dendrites. No neuron ever has more than one axon. Most axons branch, in some cases very profusely. Axons make contact with other cells, usually other neurons but sometimes muscle or gland cells, at junctions known as synapses. At a synapse, the membrane of the axon closely adjoins the membrane of the target cell, and special molecular structures serve to transmit electrical or electrochemical signals across the gap. Some synaptic junctions appear partway along an axon as it extends—these are called en passant ("in passing") synapses. Other synapses appear as terminals at the ends of axonal branches. A single axon, with all its branches taken together, can innervate multiple parts of the brain and generate thousands of synaptic terminals.
Typical Symptoms of Demylenation include :
- Blurriness in the central visual field that affects only one eye.
- Double vision.
- Odd sensation in legs, arms, chest, or face.
- weakness of arms or legs.
- Cognitive disruption.
- Heat sensitivity.
- Loss of dexterity.
- Difficulty coordinating movement or balance.
- Difficulty controlling bowel movements or urination.
- Fatigue.
Notes.
Amacrine cells are interneurons in the retina. Amacrine cells are responsible for 70% of input to retinal ganglion cells. Bipolar cells, which are responsible for the other 30% of input to retinal ganglia, are regulated by amacrine cells.
Nodes of Ranvier -
Electrochemical impulse
