2
$\begingroup$

I am having trouble visualizing/grasping the necessity of alpha-gamma co-activation. My understanding is the following:

When an external load causes stretching of the sensory muscle spindles, the 1a afferent fibers travel via the DRG and synapse on both alpha and gamma motor neurons in the anterior horn of the spinal cord. The alpha motor neuron then relays an efferent signal to the extrafusal muscle fibers and induces a contraction. Almost simultaneously, the gamma motor neuron relays an efferent signal to muscle spindles, causing the contraction of the intrafusal muscle fibers at their polar regions, and stretching at their equatorial regions. The stretching of the equatorial regions is what causes the 1a sensory fiber afferents to relay signals to the spinal cord.

Herein lies my problem. If muscle spindles can only relay their afferent signals to the spinal cord AFTER gamma activation, but gamma activation requires muscle spindle afferent signals, wouldn't this be a catch 22? Also, I read from a few sources that gamma activation, while almost simultaneous, occurs after alpha activation. Wouldn't the converse make more sense as gamma activation would trigger higher alpha firing frequency?

I hope my question makes sense. This is my first time making a post on this forum so I do apologize if the syntax of my question is not in accordance with proper question formatting.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.