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Flashcards in The Nerve Impulse Deck (11):

Define nerve impulse

A self-propagating wave of electrical disturbance that travels along the surface of the axon membrane


What are the two states of a nerve impulse?

The resting potential and action potential


During a resting potential, how is the movement of sodium and potassium ions, across the axon membrane controlled?

The phospholipid bilayer, intrinsic proteins and by sodium-potassium pumps


What is resting potential?

Where the inside of an axon is negatively charged relative to the outside and ranges from 50-90 millivolts


During the resting potential, what condition is the axon said to be in?

It is said to be polarised


What happens to the sodium and potassium ions during the resting potential to establish the difference in charge between the inside and the outside of the axon?

Sodium ions are actively transported out of the axon while potassium ions are actively transported into the axon by sodium-potassium pumps


What is the ratio of sodium ions that are actively transported compared to potassium ions?

3 sodium : 2 potassium


What does the difference in the concentration of sodium and potassium ions create?

A chemical gradient between the cytoplasm and the tissue fluid surrounding the axon


What makes the axon membrane more permeable to potassium ions?

Most of the gates in the channels that allow potassium ions to move through are open compared to most of the sodium gated channels which are closed


What other sort of gradient causes the movement of potassium and sodium ions?

An electrical gradient


When is an equilibrium established ?

When the chemical and electrical gradients are balanced and there is no net movement of ions