1-06 The Nerve Impulse (Part 2)

Front 1

Objective

Describe the process of propagation of the action potential.

Back 1

Sodium ions that enter during an action potential migrate along the inside of the membrane, causing the depolarization of adjacent areas. This slight depolarization is what triggers the action potential in the adjacent areas. As a result, the action potential spreads along the surface of the membrane.

Front 2

Objective

Explain how saltatory conduction works.

Back 2

There are short sections between each segment of myelin sheath. These areas, called Nodes of Ranvier, are completely unmyelinated and therefore have no electrical insulation. The action potential literally jumps from node to node, as follows: The sodium ions that enter at a specific node repel other positively-charged ions, causing them to migrate along the inside of the membrane to the next node, where they trigger a new action potential.

Front 3

Objective

Indicate when impulses are transmitted without action potentials.

Back 3

Local neurons, in which axons only travel a short distance, can use graded potentials that do not follow the all-or-nothing law. In these potentials, the depolarization of the membrane is a function of stimulus intensity: i.e., a more intense stimulus produces a larger potential.

Front 4

axon hillock

Back 4

The swelling of the cell body where the axon begins

Front 5

propagation of the action potential

Back 5

The transmission of an action potential along the membrane of an axon