Xref: utzoo bionet.general:1384 sci.med:23591 sci.med.physics:281 Path: utzoo!news-server.csri.toronto.edu!rutgers!bionet!news.cs.indiana.edu!samsung!zaphod.mps.ohio-state.edu!swrinde!ucsd!casbah.acns.nwu.edu!sundeep From: sundeep@casbah.acns.nwu.edu (Sundeep Gupta) Newsgroups: bionet.general,sci.med,sci.med.physics Subject: Re: Question on Speed of Human REFLEX System Keywords: SPEED OF HUMAN REFLEX SYSTEM Message-ID: <1991Mar13.213817.9967@casbah.acns.nwu.edu> Date: 13 Mar 91 21:38:17 GMT References: <11929@uhccux.uhcc.Hawaii.Edu> Distribution: usa Organization: Northwestern University Lines: 40 In article <11929@uhccux.uhcc.Hawaii.Edu> leeky@wiliki.eng.hawaii.edu writes: >Hi everyone, > >Hope this is the right place to post this novice question... > >I was just wondering if anyone out there could enlighten me on a >topic regarding instantaneous speed of human reflex system. > Well, I'm just a 1st year med student, so I could be totally off base here. A reflex would include the nerve impulse travelling to the spinal cord, then through a reflex interneuron, then through an efferent neuron to the muscle being activated. After this, one would need to account for the time between the nerve impulse reaching the muscle and the contraction actually occurring. So there are four parts to the reflex. 1. Muscle tendon afferent impulses travel at about 100 m/s - from the knee to the spinal cord is approximately 1/2 meter, giving a time of 5 milliseconds. 2. The reflex interneuron impulse time should be negligible since it is only millimeters in length and even a slow nerve fiber of 50 m/s would give a time of about .02 milliseconds. 3. The efferent nerve impulse should also travel at about 100 m/s and should therefore also take about 5 milliseconds. 4. For fast twitch muscle fibers, the time between innervation and maximal contraction is about 10 milliseconds. This comes to a total of about 20 milliseconds, or 1/50th of a second. Parts of this I may not have included would be the time for synaptic transmission of the impulses between the two neuron synapses. I do not know if these are negligible or not. -- --------------------------{ Sundeep Kumar Gupta }------------------------ Internet:sundeep@casbah.acns.nwu.edu Bitnet:sundeep@nuacc uucp:gargoyle!nucsrl!casbah.acns.nwu.edu!sundeep Academic Computing and Network Services, Northwestern University