When a person voluntarily contracts the quadriceps, gamma motor neuron firing rises along with alpha motor neuron firing. What is the functional purpose of this parallel activation?

• A To inhibit antagonist muscles through the spinal interneuron pool
• B To provide extra force by recruiting intrafusal fibres into the contraction
• C To increase Golgi tendon organ sensitivity and prevent overload
• D To keep the muscle spindle taut so it can signal stretch throughout the range of shortening ✓

Explanation

Shortening of extrafusal fibres would slacken the muscle spindle and silence its afferents if the spindle stayed fixed in length. Alpha-gamma coactivation makes the polar regions of intrafusal fibres contract in parallel, keeping the central sensory region under tension so group Ia and II afferents continue reporting muscle length accurately during movement. Intrafusal fibres contribute negligible force, ruling out option B, and the Golgi organ lies in series with tendon collagen, not under gamma control.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.