Electrical Signals of Nerve Cells - The ionic basis of action potentials

9 important questions on Electrical Signals of Nerve Cells - The ionic basis of action potentials

What was found when the Na+ dependent quantitatively was examined?

A more-or-less linear relationship was found between the amplitude of the action potential and the logarithm, of the external Na+ concentration.

What can we say about Na+ and the rising phase and overshoot phase?

The resting neuronal membrane is only slightly permeable to Na+, the membrane becomes extraordinary permeable to Na+ during the rising phase and the overshoot phase of an action potential.

How is the temporary increase in Na+ permeability caused?

It results from the opening of Na+ selective channels that are closed in the resting state.
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What did the ion substitution experiments carried out by Hodgkin and Katz provided?

Confidence evidence that
  1. The resting membrane potential results from a high resting membrane permeability to K+.
  2. Depolarization during an action potential results from a transient rise in membrane Na+ permeability.

What verbally happens during the rising phase?

The membrane potential is rapidly depolarized.

To what does the overshoot phase give rise to?

To the a falling phase, in which the membrane potential rapidly repolarizes.

What happens at the undershoot phase?

The repolarization takes the membrane potential to levels even more negative than the resting membrane potential for a short time (= hyperpolarization).

How are the types of action potentials in the Purkinje fibers called? Why?

They are complex spikes, because they have several phases that result from the summation of multiple, discrete action potentials generated in different regions of the neuron.

From what do plateaus in the repolarization phase result?

From the presence of ion channels that are permeable to CA2+, and long-lasting undershoots resulting from the presence of additional types of membrane K+ channels.

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