Physiology Nervous system Lecture

Potentials 40 mv peak 60 mv 0 mv membrane potential

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Unformatted text preview: mV -90 mV action potential Na+ channels close +60 mV membrane potential 0 mV K+ channels open Na + channels open -70 mV -90 mV time more depolarization more voltage-sensitive Na+ channels open more Na+ diffuses into cell voltage-sensitive Na+ channels close (inactivated) depolarzation to threshold voltage-sensitive K+ channels open resting potential resting potential regractory periods of action potentials +60 mV refractory periods of action potentials 0 mV absolute RP relative RP neuron can fire additional Aps if its strongly depolarized membrane potential threshold -70 mV -90 mV time relative RP absolute RP ”conduction” of action potentials by axons movement of action potentials along the plasma membranes of axons -70 mV +40 mV -60 mV -70 mV -70 mV -70 mV -70 mV -70 mV non-myelinated axon AP direction of movement -70 mV +40 mV -60 mV -70 mV -70 mV -70 mV -70 mV non-myelinated axon AP (see figure 7.19, 3rd edition) (see figure 7.20, 4th edition) direction of movement the big advantage of action potentials: myelinated axon +40 mV -70 mV AP (see figure 7.20, 3rd edition) (see figure 7.21, 4th edition) +40 mV AP -70 mV -70 mV ”conduction” of action potentials by axons two factors that affect speed of action potentiala traveling along axons 1) size of axons 2) myelin or no myein small-diameter axon with no myelin medium-diameter axon with myelin thick-diameter axon with heavy myelin medium-diameter axon with myelin (recent mild damge to myelin) thick-diameter axon with heavy myelin (recent severe damge to myelin) problems with myelin loss OBJECTIVES 1) Gain an understanding of the functional organization of the nervous system. Broadly speaking, what does it do? What are its major functional parts? What neurons are associated with these functional parts? 2) Describe the primary parts of neurons and indicate their functional roles. What happens at dendrites? What happens on axons? What is myelin? Do all axons have myelin? What are nodes? 3) Explain how the membrane potential of neurons can change. Describe graded potential and know their characteristics. What is a depolarization? What is a hyperpolarization? What is happening in a neuron to produce a change in membrane potential? In what ways do graded potentials differ from action potentials? Can graded potentials be used to communicate over long distances in the nervous system? Why or why not? 4) Describe the processes involved in the production of an action potential. (Concentrate on what happens to the movement of sodium and potassium ions.) What are the major events that occur during an action potential? What makes threshold such a special membrane potential? What is happening to sodium and potassium ion channels during an action potential? What happens following a subthreshold depolarization? What happens following a suprathreshold depolarization? 5) Identify the types of refractory periods and explain what causes them. When do they occur? How long do they last? How do they effect the firing of subsequent action potentials? Why is a larger-than-normal depolarization needed during one type of refractory period to start an action potential? 6) Describe how action potentials are conducted along an axon. What factors influence the speed of action potential propagation? Do action potentials change size as they travel along axons? What is the directions that action potentials follow along axons?...
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This note was uploaded on 09/30/2013 for the course P 215 taught by Professor Mynark during the Fall '12 term at Indiana.

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