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29 Cards in this Set
- Front
- Back
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What is the units of electric charge?
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coulombs
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What is current and what are the units?
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charge/time
coulombs/sec=amps |
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What current is plotted as a negative deflection?
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Inward current
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What is a graded response?
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Greater stimulation yields greater response
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What current is plotted as a positive deflection?
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Outward current
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Are action potentials regenerative?
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Yes.
Ion channels open in response to depolarization and cause more depolarization. |
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What is the typical resting potential of neurons?
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-40 to -90 mV
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Why is the amplitude of an action potential independent of the amount of current used?
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It is an all-or-none response. Once threshold is reached the cell will depolarize towards the target potential.
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What is permeability/conductance?
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A measure of the ease of movement of molecules across a membrane
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What two pumps create the charge gradient necessary for an action potential?
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Na/K pump
Ca/H pump (Both antiport and ATPase) |
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What equation can be used to calculate a membrane potential?
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Goldman-Hodgkin-Katz equation
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What is the difference between the Nernst equation and the GHK equation?
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GHK accounts for the permeability of each ion.
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What equation is used to measure conductance/permeability of an ion?
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Ohm's Law (V=IR or V=I/conductance)
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What determines the permeability of an ion?
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the opening and closing of ion channels
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What stimuli can open/close a gated ion channel? (5)
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Voltage
Ligand Heat Light Mechanical pressure |
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At rest, what has greater permeability, Na or K? Why?
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PK>PNa
background channels that are permeable to K are open at resting potential. |
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Describe the permeability of Na and K in the initial phase of an action potential.
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Permeability shifts to favor the inward current of Na.
PNa>PK |
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Describe the permeability of Na and K in the end phase of an action potential.
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Permeability will shift back to favor the inward current of K.
PK>PNa |
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What ion has greatest permeability approaching the peak of an action potential?
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Na
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How is intensity of an action potential measured?
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as frequency
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What is the action of apamin (bee venom)?
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Blocks specific K channel
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What property of an action potential will influence the maximum frequency of the neuron? How?
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The shape of the action potential.
Effects the amount of Ca that is able to enter the cell which in turn effects the amount of NT that is released. |
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What is the only contribution of the sodium pump?
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Establishing the membrane potential
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What types of ion channels are associated with pain?
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Voltage-gated Na channels
Voltage-gated Ca channels Voltage-gated K channels Transient Receptor Potential channels |
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What is passive conduction and how far can it be conducted?
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Passive depolarization in the absence of activity--does not reach threshold.
Can be conducted with decrement over a short distance. |
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What channels give the proper boost to a depolarization to make it an active conduction?
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Na and/or Ca channels
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What neurons will conduct faster?
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Larger, myelinated neurons
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What is the movement of the action potential along a myelinated axon called?
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Saltatory conduction: Jumping node to node (of Ranvier)
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How is a signal conducted through a dendrite?
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By voltage-gated Na and Ca channels
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