c hapter t hree resting potential action potential
TRANSCRIPT
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RESTING POTENTIALComposition of the Intracellular and Extracellular Fluids
Concentrations of Ions Inside and Outside of Neuron
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RESTING POTENTIALComposition of the Intracellular and Extracellular Fluids
Measuring Charge Inside and Outside of Neuron
Electrical force: charged molecules will be attracted to areas of
opposite charge and repelled by areas of like charge.
Diffusion: molecules will move from areas of high
concentration to areas of low concentration.
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RESTING POTENTIALFactors that move molecules
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Copyright © 2004 Allyn and Bacon
RESTING POTENTIALComposition of the Intracellular and Extracellular Fluids
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Excitatory postsynaptic potentials (EPSPs) Produce slight
depolarizations Open sodium
channels
IN THE POST-SYNAPTIC NEURONAfter Neurotransmitters have Interacted with receptors
Inhibitory postsynaptic potentials (IPSPs) Produce slight
hyperpolarizations Open either chloride or
potassium channels
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IN THE POST-SYNAPTIC NEURONAfter Neurotransmitters have Interacted with receptors
Absolute refractory period: production of a subsequent action potential is
extremely unlikely or impossible.
Relative refractory period: production of a subsequent action potential is
possible in response to larger than normal stimulation.
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ACTION POTENTIALRefractory Periods
When a cell is depolarized to threshold, an action potential is produced.
Action potentials are all-or-none. Size and shape are always the same. An action potential either occurs or does not occur.
The opening of sodium channels and potassium channels in the neural membrane accounts for the rise and fall seen in a recording of an action potential.
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ACTION POTENTIALCharacteristics
Puffer fish (fugu) is a dangerous delicacy.
Puffer fish produce tetrodotoxin, which blocks sodium channels on the outside surface of the cell membrane.
When sodium can’t move into the cell, signaling stops. 20
© Jeffrey L. Rotman/CORBIS
ACTION POTENTIALWhen things go wrong…