science

[wondercat]

how are instructions conveyed to the muscles

[woofgang]

by a small electric current in the nerve fibres

[loobylu]

One of the body's sense organs is stimulated (for instance by a change in the outside environment), and this stimulus generates a nervous impulse which then travels via a sensory nerve to the brain (also known as the central nervous system). The brain coordinates this message, and then conveys instructions to the muscles and glands via set of nerves known as motor neurones. Quite a technical process!!

[darth vader]

to be pedantically precise it is via an electronic current passing through the nerves (electric deals with large quantities of volts/amps, electronic with minute quantities of volts/amps)

[anthomson]

Are you sure darth ? - I have never heard of an electronic current before. I have only ever heard the term associated with semiconductors.

[Squirrel]

So a muscle "interprets" every electrical pulse as an instruction to contract, right, because that's all a muscle can do? Can anyway explain how a muscle is told to contract a little / a lot, fast / slow, and with x amount of force? And also how a pair of muscles can hold a joint still in any position (both contract, or what?) Sorry to extend your question, but I didn't want to start a whole new thread.

[anthomson]

The muscle is made of many muscle fibres each of which can be controlled individually. So the brain is actually sending a whole load of signals to manipulate the individual fibres and make the muscle contract in the desired way. Plus as you point out we have agonist and antagonist muscles which can be combined to give even more control. I believe that the brain can cycle messages to individual fibres - causing them to contract & relax in sequence - the net result would be to hold the muscle in position.

[darth vader]

that's what i was told by my electronics master - electronics = small currents (semi-conductor technology etc) electrics = large currents (kettles, cookers etc)

[darth vader]

...if electronics don't have currents then how do they work?

[anthomson]

I would guess the term electronic originally refered to the behaviour of single electrons skipping from a cathode thru a vacuum (or gas) to the anode and then was applied to transistors and semiconductors which work on the same principle. As this doesn't happen in the body I would say it is just a very small electric current rather than an electronic current.