Physiology

Inhibitory interneurons make it harder for action potential to fire. They work by allowing GABA to bind to transmembrane receptors that allow chloride ions into the cell. This binding makes the membrane potential more negative and the threshold for action potential harder to be achieved. If these were changed to excitatory in the stretch reflex, functions to maintain the muscle at a constant length would fail. As soon as the stretched muscle began to contract the antagonist muscle would stretch & both muscles would contract simultaneously.