biopsych 2 - Chapter 4 Membrane potential- the difference...

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Chapter 4 Membrane potential- the difference in electrical charge between the inside and the outside of a cell. Microelectrodes- extremely fine recording electrodes, which are used for intracellular recording. Resting potential- the steady membrane potential of a neuron at rest, usually about -70 mV. Ion channels- pores in neural membranes through which specific ions pass Sodium-potassium pumps- active transport mechanisms that pump Na+ ions out of neurons and K+ ions in. Depolarize- to decrease the resting membrane potential. Hyperpolarize- to increase the resting membrane potential. Excitatory postsynaptic potentials (EPSPs)- graded postsynaptic depolarizations, which increase the likelihood that an action potential will be generated. Inhibitory postsynaptic potentials (IPSPs)- graded postsunaptic hyperpolarizations, which decrease the likelihood that an action potential will be generated. Graded responses- responses whose magnitude is indicative of the magnitude of the stimuli that induce them. Axon hillock- the conical structure at the junction between the axon and cell body. Threshold of excitation- the level of depolarization necessary to generate an action potential, usually about 65 mV. Action potential (AP)- a massive momentary reversal of a neuron’s membrane potential from about -70mV to about +50 mV. All-or-none responses- responses that are not graded, that either occur to their full extent or not at all. Integration- adding or combining a number of individual signals into one overall signal. Spatial summation- the integration of signals that occur at different sites on the neuron’s membrane
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Temporal summation- the integration of neural signals that occur at different times at the same synapse. Voltage-activated ion channels- ion channels that open and close in response to changes in the level of the membrane potential. Absolute refractory period- a brief period (typically 1 to 2 milliseconds) after the initiation of an action potential during which it is impossible to elicit another action potential in the same neuron. Relative refractory period- a period after the absolute refractory period during which a higher-than-normal amount of stimulation is necessary to make a neuron fire. Antidromic conduction- axonal conduction opposite to the normal direction; conduction from axon terminals back toward the cell body. Orthodromic conduction- axonal conduction in the normal direction—from the cell body toward the terminal buttons Nodes of Ranvier- the gaps between adjacent myelin segments on an axon. Salutatory conduction- conduction of an action potential from one node of Ranvier to the next along a myelinated axon. Dendtiric spines- tiny nodules of various shapes that are located on the surfaces of many dendrites and are the sites of most excitatory synapses in the mature mammalian brain Presynaptic inhibition- a form of inhibition that reduces a neuron’s responsiveness to specific synaptic input and is mediated by excitatory axoaxonal synapses. Postsynaptic inhibition- a form of inhibition that reduces a neuron’s responsiveness to all
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This note was uploaded on 03/17/2008 for the course PSYC 2012 taught by Professor Bashinski, during the Fall '06 term at Colorado.

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biopsych 2 - Chapter 4 Membrane potential- the difference...

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