During an action potential of a neuron, the type of ion that enters the cell and causes depolarization is the ion.

What cation (positive charged ion) rushes into the cell during depolarization period of action potential?

A recently depolarized area of a cell membrane cannot generate an action potential because of theMultiple Choiceabsolute refractory period.high concentration of sodium ions in the extracellular fluid.the high concentration of potassium ions in the cytoplasm.presence of receptor sites on the membrane.

Complete the sentences describing the events that occur during an action potential.An action potential will not occur unless the membrane potential at the (the initial segment of the axon) reaches a level called .When threshold is reached, of the initial segment open briefly, allowing to diffuse into the cell.As these ions enter the cell, the cell membrane undergoes , with the membrane potential increasing to a peak of approximately +30mV.As the peak of the action potential is reached, the sodium channels close and the open, allowing these ions to diffuse out of the cell.As cations leave the cell, the membrane potential at that part of the membrane once again becomes negative. This phase of the action potential is called , because the resting membrane potential is being reestablished.The membrane potential actually dips lower than -70mV because the potassium channels do not close quickly enough. This phase is called .

What is produced when depolarization of a cell membrane reaches threshold?Multiple ChoiceA new action potential is produced.An existing action potential is stopped.Voltage-gated ion channels close.The absolute refractory period ends.

When an action potential arrives at the neuromuscular junction, the wave of depolarisation triggers the opening of voltage-gated channels. Which ion passes through these voltage-gated channels?Select one alternative:SodiumChlorideCalciumPotassium