Question

If you stand within a door frame and extend both of your arms straight out to touch the frame and continually press against it, then you are maintaining a constant muscle contraction. Meanwhile, the gamma moto-neurons are stimulating the spindles and increasing their sensitivity, without affecting muscle spindle length. Therefore, when you step out of the door frame, gravity pulls your arms down causing the stretch and subsequent activation of the spindle leading to spindle activation of muscle contraction.

Mechanistically, what actually happened to your arms as you walked away from the doorway with your arms relaxed? Make sure that you describe the sequence of events in order, using the terms alpha motor neuron, central nervous system, contraction, extrafusal fibers, gravity, intrafusal fibers, sensory neuron, and stretch. Note: The terms are not listed in the correct sequence!