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Nerve Cells

Science 8: "The Cell" Project

Cheyenne Goh

on 17 December 2012

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Transcript of Nerve Cells

Nerve Cells (Neurons) Cheyenne Goh, 8B Cell Membrane 1 Basic Animal Cell Organelles Chromosomes 2 Mitochondria 3 Ribosomes 4 What are nerve cells? Endoplasmic Reticulum 5 Golgi Bodies (Apparatus) 6 Cytoplasm 7 Nucleus 8 Nucleolus 9 Lysosomes 10 Vacuoles 11 The cell membrane is a semi-permeable membrane consisting of lipids (mostly glycerophospholipids and cholesterol) and proteins that protect and organise the cell. There are different types of transmembrane proteins in the cell membrane, including transporters, receptors, enzymes, and anchors. These different proteins are specific and selective for the molecules in which they carry, bind, transform, etc. Transport proteins allow the cell to accumulate nutrients in high concentrations, and dispose of waste products by carrying specific molecules in and out of the cell. Chromosomes are single, long molecules of DNA that store genetic information in living organisms. Depending on the organism, these highly organized structures can be linear or circular and are often observed and depicted as being X-shaped. Genes (small sections of the chromosome) code for the RNA and protein molecules required by an organism. Eukaryotic chromosomes are stored in the nucleus and is composed of DNA coiled and condensed around nuclear proteins called histones. The mitochondria produce energy for a cell in the form of an energy-rich molecule called adenosine triphosphate (ATP) by using energy stored in food through the process of respiration (using oxygen to generate energy). The ribosomes of a cell are composed of rRNA and protein and consist of the 40S and 60S subunits. They can either be attached to the endoplasmic reticulum, or free in the cytoplasm. Ribosomes receive and translate genetic instructions for the formation of specific proteins or polypeptides. During a translation, the two ribosomal subunits join together and form a complete ribosome. The endoplasmic reticulum is a network of cisternae (membrane-enclosed tubules and sacs) that extends from the nuclear membrane throughout the cytoplasm. It's usually the largest organelle and is made up of two distinct types: the rough ER and smooth ER. The rough ER functions in protein processing, whereas the smooth ER is involved with lipid metabolism. The golgi apparatus receives biochemicals in 'bulk flow' from the rough ER, then sorts, modifies, concentrates, packs and dispatches the biochemicals for use inside and outside of the cell. They are mainly transported to lysosomes, the cell membrane, and the outside of the cell. Cytoplasm is a thick solution, mainly composed of water, salts, and proteins. It fills each cell and enclosed by the cell membrane. It appears to have no form or structure, but it is highly organised. The cytoskeleton, a framework of protein scaffolds, provides structure for the cytoplasm and cell. The nucleus stores DNA (hereditary material) and coordinates the cell's activities, including intermediary metabolism, growth, protein synthesis, and reproduction (cell division). It takes up approximately 10 percent of a cell's volume and consists mostly of chromatin, the unstructured form of DNA that will organize to form chromosomes during mitosis or cell division. It is surrounded by the nuclear envelope, a selectively-permeable membrane that allows specific types and sizes of molecules to pass back and forth between the nucleus and cytoplasm. The nucleolus is a small, dense body that is not bounded by a limiting membrane. It is rich in RNA and protein and its prime function is to transcribe nucleolar DNA into 45S ribosomal-precursor RNA and processing this into 5.8S, 18S, and 28S components of ribosomal RNA. When these components associate with 5S RNA and proteins synthesized outside the nucleolus, it results in the formation of ribonucleoprotein precursors; these pass into the cytoplasm and mature into the 40S and 60S subunits of the ribosome. The lysosomes contain an array of enzymes that break down biological polymers—proteins, nucleic acid, carbohydrates, and lipids. They degrade material taken up from outside the cell through endocytosis, as well as digest obsolete components of the cell itself derived from phagocytosis and autophagy. Vacuoles are tiny fluid-filled cavities in the cytoplasm that are composed mainly of phospholipids since they were formed from the cell membrane. In eukaryotic cells, vacuoles are responsible for capturing food materials and unwanted structural debris, sequestering toxic materials in the cell, maintaining fluid balance and turgor pressure, and determining the relative size of the cell. They work by pumping potassium ions of the cell because water follows the solute of potassium ions by diffusion to move in or out the cell. 1 3 4 5 6 7 8 9 2 Not illustrated on this diagram. 7 10 11 Nerve cells, or neurons, are the millions messenger cells in your nervous system that to transmit messages across your body. Neurons contain a cell body and one or more fibres that range from microscopic to over one metre in length. There are two different types of nerve fibres: dendrites and axons. Dendrites carry information towards the cell body, whereas axons carry them away from it. Tight bundles of nerve fibres make up nerves. There are three types of neurons. Sensory neurons pass information about stimuli (such as light, heat, sound, pressure, or chemicals) from inside and outside your body to your central nervous system. Motor neurons pass instructions from your central nervous system to other parts of your body, such as muscles and glands. Association neurons connect your other two types of neurons. Neurons carry messages in the form nerve impulses (electrical signals carrying messages). Nerve impulses are created when your nerves get excited by stimuli or, in most cases, neurotransmitters (chemicals released by other neurons). Although the millions of neurons within your nervous system are densely packed, they never touch. When a nerve impulse reaches the end of one neuron, a neurotransmitter is released and diffuses from this neuron across a junction to excite the next neuron. However, over half of the nerve cells in your nervous system are supporting nerve cells that do not transmit impulses. These cells are found between and around other neurons to insulate, protect, and nourish them. Bibliography http://www.elin.ttu.ee/mesel/Study/Courses/Biomedel/Content/BioElect/ProcPhen/99_cell_dendrite0.jpg http://www.chiefscientist.gov.au/wp-content/uploads/Synapses-Image-for-March-17-2010-Blog-Entry.JPG http://www.vetenskaphalsa.se/wp-content/uploads/2010/07/Animal-cell-cut-away-scientifically-correct-3d-illustration_dreamstime_13626492.jpg http://journalofcosmology.com/Cosmology2.html http://www.buzzle.com/articles/labeled-animal-cell-diagram.html http://caps.nwcreation.net/2008/05/16/2008-may-18-caps-presentation-of-the-wonders-of-the-cell-by-chris-ashcraft/ http://www.nature.com/scitable/topicpage/cell-membranes-14052567 http://www.nature.com/scitable/definition/chromosome-chromosomes-eukaryotic-chromosome-eucariotic-chromosome-procariotic-6 http://hyperphysics.phy-astr.gsu.edu/hbase/biology/mitochondria.html http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit3/eustruct/riboeu.html http://www.ncbi.nlm.nih.gov/books/NBK9889/ http://www.bscb.org/?url=softcell/golgi http://www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/anatomy/animalcellstructure/nucleus/nucleus.htm http://www.ebi.ac.uk/QuickGO/GTerm?id=GO:0005730 http://www.ncbi.nlm.nih.gov/books/NBK9953/ http://faculty.muhs.edu/klestinski/cellcity/vacuoledata.htm http://www.bbc.co.uk/science/humanbody/body/factfiles/nervecellsandnerves/nerve_cells_and_nerves.shtml Alright. Now that you know what a nerve cell is, let's go for what I like to call the "Tour de Neuron". For each organelle, you will see where it is on the 3D diagram and/or the illustrated diagram of a basic animal cell. In addition to that, you will also see where it's found on the diagram of the nerve cell. Enough said. Bon voyage!
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