Chronaxie

Chronaxie is a concept in electrophysiology that refers to the minimum time over which an electric current double the rheobase needs to be applied to a neuron or muscle fiber to trigger an action potential. It is a measure of the excitability or responsiveness of a nerve or muscle cell to electrical stimulation.

History

The term "chronaxie" was first introduced by Louis Lapicque in 1907. Lapicque was a French physiologist who used the concept to describe the time required for an electrical stimulus of twice the threshold intensity to stimulate a nerve or muscle cell.

Measurement

Chronaxie is measured in milliseconds (ms) and is used to determine the type of nerve or muscle fiber. For instance, the chronaxie for motor nerves is about 0.5 ms, sensory nerves about 0.2 ms, and pain fibers about 1 ms.

Clinical significance

Chronaxie measurements can be used in the diagnosis and treatment of various neuromuscular disorders. For example, a prolonged chronaxie may indicate a neuropathy or myopathy, while a shortened chronaxie may suggest a hyperexcitability disorder such as tetany or myotonia.

See also

• Strength-duration curve
• Rheobase
• Electrophysiology
• Neuromuscular junction