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Nervous System

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Nathan Dorr

on 3 May 2013

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Transcript of Nervous System

By: Nathan, Josh, and Alec Nervous System The nervous system is a network of nerve cells and fibers that transmits nerve impulses between parts of the body. What is the Nervous System? 1. Central Nervous System:
Located near the Brain and Spinal Cord. Two Main Parts . Picture of Nervous System Throughout the Body When a nerve reaches its action potential due to change in the charge of the cell, an electric pulse is released, which then causes neurotransmitters to be released across a synapse to another nerve cell which does this again. However, before any of this occurs the cell must reach its resting potential. Let's look at this video for further explanation. How does a nerve send a signal? An action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, causing a signal to continue through the axon and neurotransmitters to be sent. This video will help clarify: What is an Action Potential and how does is work? Nerve cells are made of three main sections: the cell body, axons, and dendrites. There are also Schwann cells and Nodes of Ranvier. What Makes Up a Nerve Cell? 2. Peripheral Nervous System:
Located outside the Brain and the Spinal Cord. The -70, -55 Threshold Generally, nerve cells rest at -70 millivolts, however when an initiation occurs and the charge changes to at or above -55 millivolts then an action potential is reached and the signal continues. Afferent vs. Efferent Afferent neurons (Sensory nuerons) carry signals to a central point while efferent neurons(motor neurons) carry signals away from the brain. Neurotransmitters Acetylcholine: Is found in both nervous systems and is the most common neurotransmitter. Epinephrine: Adrenaline (Fight or Flight) Norepinephrine: An increase in this causes the sympathetic nervous system to increase the rate of heart contractions. Dopamine: Chemical messenger that helps in the transmission of signals in the brain and other vital areas. Serotonin: Thought to be a contributor to feelings of well-being and happiness. GABA The chief inhibitory neurotransmitter in the vertebrate central nervous system. Types of Nervous Systems Automatic Nervous System: Controls everything that you don't think about (Breathing, Digestion, Heartbeat). Somatic Nervous System: Controls everything that you do think about (walking, talking, eating). Types of Transmitters Excitatory: A positive neurotransmitter that tells an action to continue. Inhibitory: A negative neurotransmitter that tells an action not to continue. Schwann Cells Form from the myelin sheath and are separated by gaps of unsheated axon over which the impulse travels as the signal propagates along the neuron. Nodes of Ranvier The gaps between the myelin Polarized Nuerons vs Non-Polarized Nuerons A neuron is said to be polarized because the voltage within the neuron (intracellular) is negative relative to the voltage outside the neuron (extracellular) - when the neuron is at rest. While a non-polarizd nueron is the opposite.
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