The Action Potential An action potential‚ also called a spike‚ nerve impulse‚ and discharge‚ is the rapid reversal of charge of the cell membrane. These changes in charge occur within milliseconds‚ meaning the action potential travels very quickly down the axon in order to convey information over long distances. This transfer of information occurs within six phases and requires the presence of multiple pumps and channels embedded in the membrane to control ion concentration. Phase 1: The Resting
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The Action Potential Graphics are used with permission of: Pearson Education Inc.‚ publishing as Benjamin Cummings (http://www.aw-bc.com) ** If this is not printed in color‚ it is suggested you color code the ion channels and ions as you go through this topic. Ions channels and ions should be color coded as follows: Red: Sodium ion channels and sodium ions Blue: Potassium ion channels and potassium ions Page 1. Introduction • Neurons communicate over
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fundamental unit of the nervous system. These neurons work together with other excitable cells to produce action potentials when they receive electrical or chemical stimuli. Action potentials can be thought of as an “all-or-nothing” event and occur as a large-scale depolarization when sodium and other positive ions rapidly enter the neuron through membrane channel proteins. Once initiated‚ action potentials travel down the length of the axon and when it reaches the end a neurotransmitter is released into
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neuron. Axon hillock‚ action potential The area where the axon emerges from the soma (cell body) is called the ___ ___. This is also where the outgoing signal‚ called a/an ___ ___ is generated. Collaterals‚ terminals An axon can branch‚ forming many axon ___. At the end‚ axons branch to form many axon ___. Schwann cells What support cell forms the myelin sheath? Integral proteins What structures in the cell membrane function as ion channels? 1) Charge 2) Size 3) How much water
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Exercise 3: Neurophysiology of Nerve Impulses: Activity 2: Receptor Potential Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. Assuming that the resting potential of a sensory neuron is -70 mV‚ which of the following represents a depolarization? You correctly answered: c. a change to -60 mV 2. Which of the following is a sensory modality (type of sense)? You correctly answered: e. all of the above 3. Which of the following is a sensory stimulus
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ckingmotherCoordination by Neural Signaling 26.1 Invertebrates reflect an evolutionary trend toward bilateral symmetry and cephalization * Invertebrate Nervous Organization * In simple animals‚ such as sponges‚ the most common observable response is closure of the osculum (central opening) * Hydras (cnidarians) have a nerve net that is composed of neurons * Planarians‚ (flatworms) have a ladderlike nervous system * In annelids (earthworm)‚ arthropods (crab)‚ and
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1. a. The action potential changes the membrane potential from -70 mV (resting) to +30 mV and back again to the resting membrane potential. b. This results from a change in membrane permeability first to Na then to K due to the opening of what type of ion channels? Voltage gated channels 2. a. Where is the density of voltage-gated Na+ channels the greatest? Axon hillock b. What areas of the neuron generate signals that open these voltage-gated channels? Dendrites and the cell body c. Opening
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that bring 2 potassium ions into the cell‚ for every 3 sodium ions it pumps out. As well as this‚ there are protein channels which allow potassium ions in the cell to flow out via facilitated diffusion. Potassium diffuses out the cell much more readily than sodium diffuses in. Lastly there are many negatively charged organic anions such as some amino acids inside the cell. These three factors give rise the the difference in charge between the inside and the outside of
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different electrode sites. The amplitude and the shape of the signals depend upon the position of the electrodes (Brown‚ 1999) (Conover‚ 1992). The SA node produces the pacemaker potential and if this reaches the threshold then an action potential is generated. There are five stages involved during cardiac action potentials‚ during these stages there is a flow of ions through
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The Ionic mechanism and propagation of action potentials. The action potential is the result of a large‚ sudden increase in sodium permeability of the membrane. The resulting rush of sodium ions into the membrane and accumulation of positive charge on its inner surface drives the potential towards Ena. This is followed by repolarisation‚ whereby there is a large increase in the membranes permeability to potassium ions‚ hence the membrane returns to Ek. Explanation of the (ionic) mechanisms underlying
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