What happens to alpha motor neuron activity when tissue is heated?

• A. Decreased alpha motor neuron activity
• B. Increased alpha motor neuron activity
• C. No change
• D. Fluctuates unpredictably

Answer: (A)

Heating tissue tends to dampen the signals that drive muscle contraction. When tissue warms, the nervous system shifts toward relaxing the muscle by reducing the discharge of alpha motor neurons. This happens because warmer tissue lowers muscle spindle sensitivity and increases inhibitory input within spinal circuits, which together decrease the excitatory drive to alpha motor neurons. The net effect is less recruitment of motor units and a lower firing rate, producing muscle relaxation. While nerve conduction velocity can speed up with heat, the overall motor output is reduced due to these reflex and spindle-related changes. So decreased alpha motor neuron activity aligns with the relaxant effect of heating.