(neuroscience) A brief period of time following the stimulation of a nerve during which the nerve will not respond to a second stimulus.
| Sci-Tech Dictionary: refractory period |
(neuroscience) A brief period of time following the stimulation of a nerve during which the nerve will not respond to a second stimulus.
| World of the Body: refractory period |
Signals are transmitted around the nervous system, along the fibres (axons) of nerve cells, in the form of electrical impulses called action potentials. After an action potential has swept along a single nerve fibre, a second nerve impulse cannot be initiated immediately. Instead a finite time, known as the refractory period, must elapse before another action potential can be generated in response to a further stimulus (such as an electric shock to the nerve). Neurophysiologists sometimes divide this interval into the absolute refractory period, during which a second action potential cannot be elicited, no matter how strong the stimulus, and the relative refractory period, during which a second action potential can be evoked, but only if the stimulus strength is increased.
The refractory period sets a limit on the frequency at which action potentials can be conducted along single nerve fibres. In mammals, the absolute refractory period is about 1 millisecond and the maximum firing frequency is around 1000 impulses per second (although it is rare for fibres to fire naturally at rates above a few hundred per second). Some animals manage faster rates: the Gymnotid electric fish of South America, for example, can transmit impulses at rates of up to 1600 per second.
The refractory period is a consequence of the molecular processes that underlie the action potential. Action potentials are elicited when tiny pores in the nerve cell membrane, known as sodium channels, open up in response to a stimulus. The sodium channels can exist in three different states: closed, open, and inactivated. At rest, the sodium channels are closed. In response to electrical stimulation, the sodium channels open, but they then pass into the inactivated state, in which the pore is closed but the channel is unable to open in response to a further stimulus. It takes some time for the sodium channels to recover from inactivation and return to the closed state, even after the action potential is over and the nerve cell membrane has returned to its resting state. During this time, the nerve is refractory to stimulation. The refractory period thus reflects the time it takes for the sodium channels to recover.
— Frances M. Ashcroft
Bibliography
See also action potential.
| Sports Science and Medicine: refractory period |
If absolute, a period of total inexcitability of a nerve or muscle cell immediately following stimulation. After this absolute refractory period, there is a relative refractory period during which only a stronger than normal stimulus can excite the nerve or muscle.
| Wikipedia: Refractory period |
The term "refractory period" may refer to:
| This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article. |
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| action potentials | |
| relative refractory period | |
| twitch |
| Why is absolute refractory period necessary? | |
| What is the role of refractory period in fatigue? | |
| What is the actual refractory potential period? |
Copyrights:
![]() | Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved. Read more | |
![]() | World of the Body. The Oxford Companion to the Body. Copyright © 2001, 2003 by Oxford University Press. All rights reserved. Read more | |
![]() | Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved. Read more | |
![]() | Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Refractory period". Read more |