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A Review of the Neuron! Nerve cells are called neurons. The human brain has about one billion neurons. Each neuron is a cell that uses biochemical reactions to receive, process, and transmit information. In simple terms, a neuron is a cell specialized to conduct and generate electrical impulses and to carry information from one part of the brain to another. Thanks to their numerous branch-like processes, neurons interconnect forming a massive network of "wires" that extend throughout the body. By sending messages across this network, the different parts of the human body interact and communicate with each other. How Neurons Communicate Neurons communicate through an electrochemical process. Sensory receptors interact with stimuli such as light, sound, temperature, and pain which is transformed into a code that is carried to the brain by a chain of neurons. Then systems of neurons in the brain interpret this information. The information is carried along axons and dendrites because of changes in electrical properties which we call action potential. An action potential is initiated when a messenger attaches itself to a receptor. When that occurs, an electrical signal is triggered to be generated through the neuron. Once the signal reaches the end of an axon, which is at the end of a neuron, a neurotransmitter is released and the process repeats. There are several different types of neurons. Sensory neurons carry signals from the outer parts of your body into the central nervous system or CNS. For example, if somebody puts ice on your hand, the sensory neurons send the message from your hand to your central nervous system telling you the ice is cold. Motor neurons carry signals from the central nervous system to the outer parts of your body doing the opposite of sensory neurons. For example, if you were driving, the motor neurons would take the message from your central nervous system to your hand telling you to turn the key. Receptors sense the environment and encode this information into electrochemical messages sent by sensory neurons. Inter neurons act as highways or bridges connecting neurons within the brain and spinal cord. Axons and Dendrites Axons Dendrites Take information away from the cell body Bring information to the cell body Have a smooth surface Have a rough surface Only one axon per cell Many dendrites per cell No ribosome Have ribosome Have myelin No myelin Branch far from the cell body Branch near the cell body Time to answer some questions!! 1. There are three different kinds of neurons or nerve cells. Match each kind with its function. A. Motor neuron; B. Sensory neuron; C. Relay neuron; Kind of neuron Function ................................... The nerve cell that carries impulses from a sense receptor to the brain or spinal cord. .................................... The nerve cell that connects sensory and motor neurons ..................................... The nerve cell that transmits impulses from the brain or spinal cord to a muscle or gland 2. Functions related to neurons is given below; find the correct term and see if you can label the diagram of the neuron that you were given (separate sheet). The words to label are in bold Term Function The long fibre that carries the nerve impulses. A bundle of axons. The connection between adjacent neurons. The chemical secreted into the gap between neurons at a synapse. A rapid automatic response to a stimulus. The covering of fatty material that speeds up the passage of nerve impulses. The structure at the end of an axon that produces neurotransmitters to transmit the nerve impulse across the synapse. The high speed signals that pass along the axons of nerve cells. The branching filaments that conduct nerve impulses towards the cell. The sense organ or cells that receive stimuli from within and outside the body. The reaction to a stimulus by a muscle or gland. The part of the nerve cell containing the nucleus. Gaps that occur long the axon between the sections of myelin. Allow signals to jump from node to mode and therefore travel faster Associate (glial cells) that produce the myelin sheath on axons (*bonus!) 3. Indicate whether the following parts of the nervous system are part of the Central Nervous System CNS) or the Peripheral Nervous System (PNS). Part of nervous system CNS or PNS? Brain ........................ Autonomic nervous system ........................ Spinal nerves ........................ Spinal cord ........................ Cranial nerves .........................