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Nervous System

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Nervous System Coursework The Nervous System is the most complex and delicate of all the body systems. At the centre of the nervous system is the brain. The brain sends and receives messages through a network of nerves. This network can be explained as similar to a road network. The spinal cord is a thick bundle of nerves which runs down the centre of the spine. This is like a freeway. Along the spinal cord smaller bunches of nerves branch out. These are like highways From these bundles, smaller bundles of nerves branch out again. These are like main roads. Finally, individual nerves branch out to every part of the body. These are like normal roads. This network of nerves allows the brain to communicate with every part of the body. Nerves transmit information as electrical impulses from one area of the body to another. Some nerves carry information to the brain. This allows us to see, hear, smell, taste and touch. Other nerves carry information from the brain to the muscles to control our body's movement. Many drugs, such as alcohol and cigarettes, affect the way that our nerves work. This can result in us not being able to control our body, as well as we should. ...read more.


Glial cells are more abundant than neurones; there are ten times as many glial cells as neurones. Glial Cells * Astrocytes * Epidermal Cells * Microglia * Oligodendrocytes * Schwann cells Schwann cells * Cells which form the specialised myelin sheath of axons in the peripheral nervous system * The plasma membrane may wrap itself around an axon up to 100 times, making the myelin sheath a white fatty material. Summary of functions attributed to glial cells: * electrical activity * support nutrition of neurones * secretion and storage of neurotransmitters * proliferate to fill atrophied areas of the brain * support for regeneration of damaged neurones * mechanical support * electrical insulation * blood-brain barrier * Control ionic composition of extra-cellular fluid. Morphological nerve cell types 'Networks' of neurons * neurons communicate across the synapse by using chemical messengers called neurotransmitters * neurotransmitters may act to inhibit neurons or to excite neurons * attachment of the neurotransmitters to pre-synaptic membrane receptors causes ion channels to open �Information flow is usually in one direction (dendrites to synapses) Gaps in the myelin sheath are formed between the bits of myelin provided by individual Schwann cells. These nodes of Ranvier are where the electrical signal is regenerated Reflex action * A reflex action is a very rapid automatic (no conscious control) ...read more.


It also competes for the enzyme that normally breaks serotonin down. Neurons transmit impulses as electrical signals. These signals travel very rapidly along their cell surface membrane. These signals are not a flow of electrons like an a electrical current but very brief changes in the distribution of charges cross the cell surface membrane, caused by the very rapid movement of sodium and potassium ions into and out of the axon. These movements are by diffusion and active transport. Diffusion is when the ions move from high concentration to a low concentration active transport is when ions are pumped against the concentration gradient using energy from ATP. Resting potential In resting potential sodium/potassium pumps Na+ out and K+ into the axon, but the membrane is much more permeable to K+ so it tends to diffuse out again along the concentration gradient. Hence there are more positive ions outside than inside so the resting potential is -65 MV. Action potential In action potential sodium channels in he membrane open an N+ ions diffuse in rapidly along the concentration gradient. Now there are more positive ions inside than outside so the action potential is +40mv. The membrane is now said to be depolarised. Return to resting potential When returning to resting potential potassium channels in the membrane open and k+ ions diffuse out along the concentration gradient. ...read more.

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