Neurons Generating and Conducting Nerve Impulses

The insides of cells are electrically negative in comparison to the outsides. The difference in electric potential, or voltage, across the plasma membrane of a cell is called its membrane potential. In an unstimulated neuron, this voltage difference is called a resting potential.

Membrane potentials can be measured with electrodes. An electrode can be made from a glass pipette pulled to a very sharp tip and filled with a solution containing ions that conduct electric charges. Using such electrodes, we can record very tiny local electrical events. If a pair of electrodes is placed one on each side of the plasma membrane of a resting axon, they measure a voltage difference of about 60 millivolts (mV) (Figure 44.4).

The resting potential provides a means for neurons to respond to a stimulus. A neuron is sensitive to any chemical or physical factor that causes a change in the resting potential across a portion of its plasma membrane. The most extreme change in membrane potential is an action potential, which is a sudden and rapid reversal in the voltage across a portion of the plasma membrane. For 1 or 2 milliseconds, a bioelectric current crosses the membrane and the inside of the cell becomes more positive than the outside. Nerve impulses are action potentials that move along axons.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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  • Walter
    What causes the voltage of 70 millivolts across the nerve cell membrane?
    7 years ago

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