gamma and alpha neurons in motor control

F. Frank LeFever flefever at
Sat Dec 19 20:54:01 EST 1998

My understanding is that these simply refer to the size (diameter) of
the axons--alpha being big and gamma being small.

The gamma fibers innervate tiny muscles within the big muscle, within
the "intrafusil cell", and- - - (my memory is tenuous after all these
years)- - -I believe their contraction relieves the stain on their
strain-guages or whatever, so a stronger contraction than would
otherwise be needed- - - - NO, maybe I've got it completely backwards.
Is it that their contraction increases the strain, so that the stretch
receptor sends signals centrally, enhancing the alpha fibers' signal to
the larger muscle, until it contracts enough to off-set the tension
established by the gamma fibers' signal to the tiny muscle in the
intrafusil cell?

My understanding is that this provided a way to "program" or "preset"
the amount of large-muscle action necessary to achieve an anticipated

Can someone with more recent education in this area and a better grasp
of both the terms and the processes help me out?

F. Frank LeFever, Ph.D.
New York Neuropsychology Group 

In <367BB99B.807397A3 at> Mark Elliott
<elliott at> writes: 
>could someone explain why neurons involved in muscle coordination are
>referred to as alpha and gamma neurons. Is it a property of their
>Mark Elliott
>Universität Leipzig.
>Institut für Allgemeine Psychologie.
>Seeburgstr. 14/20,
>D-04103 Leipzig.
>Tel: ++49 (0)341 97-35957
>elliott at
>m.elliott at

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