Does anybody have any kind of clue where I could find some information about nerve impulse voltages/currents? My thesis project involves detection of nerve impulses, and I need to know how sensitive the sensors need to be. I dont recall any type of referrence to this type of thing in any of my bio texts. granted they are kinda basic… any help would be greatly appreciated.
I’m not home so i don’t have any references in front of me, but… I seem to remember in BODY ELECTRIC by Becker (i think) that the voltages used were in the 10 maybe 20 millivolt range and that the currant measurements where single digit milliamps. Like i said, i could be wrong. If you would like, i’ll look it up when i get home.
As an electrophsyiologist studying currents in cardiac myocytes (same technology as on neurons) are measured in pA to nA…and voltages are measured in mV. Electrically, the only difference between the two are the combination of ion channels and receptors making up the current profile. Also, Neuronal Action Potentials (APs) are much much shorter…1-2 ms at most, whereas cardiac APs are a few hundred ms.
Look up information on “patch clamping”. Some great text books are Ion Channels of Excitable Membranes, by B. Hille, and Single-Channel Recording 2nd ed. by Sakmann and Nehr (Former nobel prize winners for inventing the technique). These books are very expensive (I paid $457CDN for the both) so find them at the library if you can.
If you have any other questions…please post or PM me…Glad to help. Also, it would help if you better describe what you’re aiming to measure more specifically, and I can provide more details. Hope this helps
ND
NERDS! … Just kidding, you guys sound really smart. I wish I could do some electro type tests on nerves and such. Hell the closest i’ll ever get to that is when my friend shocked me with a trick lighter the other day.
OK so I didn’t really have anything to add to this post I just wanted to tell about getting shocked with a lighter.
Later
thanks for the replies guys, I appreciate it.
I should have been more precise in my original post- I would like to detect and measure (and in turn amplify) the existing impulses (voltage and current) in the forearm/hand nerves.
My goal is to design a prosthetic that gives the user the full capability of a ‘normal’ person. I essentially want to tie into the nerves that operate the hand to detect and amplify a nerve impulse to operate the prosthetic.
Thanks again for the help.
Are you looking to measure current in “nerves” or “neurons”? (nerves are a collection of neuronal axons). I’d assume the former. I think in this case you could use probing electrodes directly into the nerve. You’d naturally need 2 probes if you’re looking to measure voltages and currents. Remember that the voltage drop is going to be dependent on the distance between probes (it’s like having numerous resistors in series…the more resistors between probes, the greater the drop). Regardless, I think you should still be measuring in mV, since the AP of a neuron goes from resting potential ~-70mV…depolarizes to +10mV…hyperpolarizes to -90mV and goes back to baseline at -70mV until the next impulse. Thus, you should still be measuring APs like this in the neurons of the hand…(Hodgkin and Huxley (another pair of Nobel Prize winners) did this in Giant Squid Axons.
Anyways, here’s another suggestion…contact Axon Instruments Inc. They manufacture digital amplifiers for electrophysiological studies, so they should be able to help you pick out the right equipment.
More questions? Just ask!
Axon Instruments used to have a book called “The Axon Guide for Electrophysiological and Biophysics Laboratory Techniques”…very useful (the version we have is from 1993, but there could be more recent versions). I mostly use the extracellular recording stuff, but here’s what they say about EMG: frequency rangle 10-2000 Hz, signal size ranges from 5 microvolts to 20 millivolts for surface recording and 50 to 1000 microvolts for invasive recording. EEG signal is from 10-300 microvolts. Hope that helps. Let me know if you have other questions, though as I said my expertise is more with single unit recording.
thanks again for the info guys. Looks like I gots me some serious reading to do.