neurobio 5 ch 4 of Bear book: the action potential part 1 (overshoot undershoot node of ranvier t
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during hyperpolarization the membrane potential becomes more _____
during depolarization the membrane potential becomes more ______
what occurs during the rising phase of action potential?
the inside of the membrane has a negative electrical potential electrical potential, there is a large driving force on sodium ions Therefore, sodium ions rush into the cell through the open sodium channels, causingthe membrane to rapidly depolarize
what happens during threshold?
threshold is the membrane potential at which enough voltage-gated sodium channels open so that the relative ionic permeability of the membrane favors sodium over potassium.
what is overshoot?
because the relative permeability of the membrane greatly favors sodium, the membrane potential goes to a value close to ENa which is greater than 0 mV
what occurs during the falling phase?
the behavior of two types of channel contributes to the falling phase. First,m the voltage gated sodium channels inactivate. Second, the voltage-gated potassium channels finally open (triggered to do so 1 msec earlier by the depolarization of the membrane). There is a great driving force on K ions when the membrane is strongly depolarized. Therefore, K ions rush out of the cell through the open channels, causing the membrane potential to become negative again.
what occurs during undershoot
the open voltage-gated potassium channels add to the resting potassium membrane permeability. Because there is very little sodium permeability, the membrane potential goes toward EK, causing a hyperpolarization relative to the resting membrane potential until the voltage gated potassium channels close again
what is the refractory period?
sodium channels inactivate when the membrane becomes strongly depolarized. They cannot be activated again and another action potential cannot be generated, until the membrane potential goes sufficiently negative to deinactivate the channels
what is orthodromic conduction of the action potential?
conduction of the action potential in one direction
what is an oscilloscope?
a sophisticated voltmeter that displays electrical signals in graphical form