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The Nervous System Your nervous system is the most complex system in your body – much of which is still a mystery to us. Your nervous system is what controls your whole body and also manages all of your intellectual activities such as memory, choice and emotions. The nervous system consists of the brain, spinal cord, sensory organs and all of the nerves which connect to the rest of the body. The central nervous system consists of the brain and spinal cord and the peripheral nervous system consists of the sense organs and sensory nerves. The Central Nervous System (CNS) The Peripheral Nervous System (PNS) Your brain consists of a cerebrum, cerebellum and spinal bulb. Your spinal cord along with your brain receives information from your sense organs and sends out instructions to all of your muscles and other organs. The central nervous system is also responsible for processing and coordinating nervous signals that are transmitted from the peripheral nervous system. The peripheral nervous system provides information to the central nervous system and also coordinates your movement. It informs your CNS about external changes detected by your senses and internal changes such as having a full bladder. It sends instructions for your conscious movement such as walking, sitting, running and also controls the functioning of your internal organs. Neurons Cells of the nervous system are called neurons. They transmit impulses in the form of electrical signals and carry information to the brain. Your brain has around 100 billion neurons that come in many different shapes and sizes. Each neuron in your brain can be connected with several thousand other neurons and can receive up to 100,000 signals a second. They are similar to other cells in your body in many ways, but they are also very different. Neurons have special cell parts called dendrites and axons. Dendrites are the branches through which a neuron receives signals from other neurons. There can be around 200 dendrites per neuron, but this varies. The axon is the nerve fibre that transmits impulses. There are three main types of neurons, based on how complicated their axons and dendrites are: 1. Unipolar These have two branches of the same axon that extend from one cell body 2. Bipolar These neurons have two completely separate axons that extend from each end of a cell body 3. Multipolar These have one axon with a number of dendrites extending from a cell body. IGNIS 13