Me Talk Pretty – Cross extensor reflex

That’s right party people we’re not done. You get two zesty physiology terms relating to the body’s response to pain for the price of one. Now that’s a value! Ok maybe I was just too lazy to include this one in our last brief chat about pain. I’m only human. Don’t make it awkward (I can feel you judging me and it’s so cold).

Well in addition to our lighting quick withdrawal from pain (NFR) orchestrated by sensory neurons, interneuron connections, and the spinal column, our body takes counter measures to maintain balance and stability. That’s right while one foot dodges sharp objects the other foot plants firmly on the ground to keep balance. Like the withdrawal reflex, this occurs within a fraction of a second as well. It is an opposing process. While flexor muscles on one side contract (for example hamstring muscles on the side of injury) the extensor muscles on the opposite side relax (quadriceps of the supporting leg relaxes to fully extend and support the weight). Once the pain receptors on the effected side are triggered by a pain stimulus (broken glass, sharp nail, etc) that signal flows down the sensory neuron like telephone wire to the spinal chord. From there the signal crosses over to the opposite side of the spinal chord to an excitatory interneuron. An alpha neuron takes it from there to its final destination, the neuromuscular junction controlling the extensor muscles in the opposite leg. This allows the weight to be evenly distributed to the support leg thereby taking pressure off of the injured side, minimizing further injury. I love a happy ending.

Stay curious, stay classy, and never stop learning my friends :-)

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