Action Potential OL rences Mailings Review View Help Tell me what you want to do

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Action Potential OL rences Mailings Review View Help Tell me what you want to do Action Potentials (21 pts) Fill in the blank or select the best term in each of the following. An action potential changes the membrane potential of a neuron from approximately -70 mV (resting) to +30 mV and then back again to resting membrane potential. This results from a change in membrane permeability first to then to due to the opening and closing of (voltage gated; chemically-gated) ion channels. These channels are located on (dendrites & cell bodies; axons) of neurons. An action potential will occur when the opening of Nat channels causes the membrane to (depolarize: repolarize; hyperpolarize) to approximately -55 mV or voltage. The initial phase of an action potential or the depolarizing phase, results when more voltage-gated (Na+LK+) open, allowing these ions to (enter, exit) the neuron. The membrane potential will rise to +30 mV and then stop when voltage-gated (No+ K+) channels become inactivated and voltage-gated (Nor, K+) channels slowly open, allowing this ion now to (enter, exit) the cell. With less Nat moving into the cell, and more K+ moving out of the cell the membrane potential novw becomes more (positive; negative) or (depolarizes,; repolarizes). Because K+ channels are slow to inactivate, excess K+ may leave the cell and the membrane potential becomes more negative than 70 ml. This is called . After an action potential, the neuron is refractory to producing a second action potential because many Na+ channels remain inactivated. The initial period is called theperiod because no stimulus is able to produce a second action potential. This time is followed by the which an action potential can be generated if the membrane is depolarized by a stimulus stronger than the initial one period in After an action potential is generated at the axon hillock it is propagated down the axorn without conduction velocity. Conduction along a myelinated axon is calledconduction and is (slower: faster) than in an unmyelinated axon. The speed at which an action potential moves along an axon is called its

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An action potential changes the membrane potential of a neuron from Approximately -70mV (resting) to +30 mV and then back again to resting membrane potential. This results from a change in membrane permeability first to increases (inside) then to decreases (outside) due to opening and closing of Voltage-gated ion channels. These channels are located on dendrites& cell bodies of neurons.

            An action potential will occur when the opening of Na+ channels causes the membrane to depolarize to approximately -55 mv or threshold voltage.

The initial phase of an action potential or the depolarizing phase, results when more voltage-gated Na+open, allowing these ions to enter the neuron. The membrane potential will rise to +30 mV and then stop when voltage-gated Na+ channels become inactivated and voltage-gated K+channels slowly open, allowing this ion now to Exit the cell.

With less Na+ moving into the cell, and more K+ moving out of the cell the membrane potential now becomes more negative or repolarizes. Because K+ channels are slow to inactivate, excess K+ may leave the cell and the membrane potential becomes more negative than -70mV. This is called Hyperpolarization.

After an action potential, the neuron is refractory to producing a second action potential because many Na+ channels remain inactivated. The initial period is called Absolute refractory period because no stimulus is able to produce the second action potential. This is followed by the Relative refractory period in which an action potential can be generated if the membrane is depolarized by a stimulus stronger than the initial one.

After an action potential is generated at the axon hillock it is propagated down the axon without a reduction in size. The speed at which an action potential moves along an axon is called conduction velocity. Conduction along the myelinated axon is called salutatory conduction and is faster than in an unmyelinated axon.

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