In part 1 we talked about the muscle spindle, how it works and how it could be involved in creating dysfunction in the body. Today I’m going to talk you through a different theory, a theory that I personally much prefer: the nociceptive reflexes.
The nociceptors are pain receptors that are present in your horse’s connective tissue, aka fascia. Before we get more into their possible role in creating dysfunction, here are a few facts about fascia that you’ll need to know to understand the effects of the nociceptors:
– Fascia has both mechanoreceptors and nociceptors that are linked with the central nervous system (brain and spinal cord) to keep it informed of what’s going on in the tissue.
– Some of those receptors are linked with the sympathetic nervous system, the system of stress.
– Fascia has the capacity, thanks to certain cells called fibroblasts, to modify its density depending on external forces and use.
– Fascia is not only around your horse’s muscles, but also around the organs, intestines, bones, and nervous system!
Now that you have those information, let’s get to it
The nociceptors are stimulated whenever something that might injure the body happens. So it can be an obvious fall, or a kick, but it can also be something more subtle, like a saddle that just doesn’t fit well, or a shoe that’s too narrow, or the ground that’s too deep or too hard… There are many more examples, but basically anything from a micro trauma to a ful on injury will stimulate the nociceptors.
So what happens once they’ve been stimulated? Well, quite a lot.
First of all, no matter how small the stimulation is, you will always get a direct response from the tissue concerned, which will start creating inflammatory substances. This is going to lower the pain threshold of the area, making it easier for the nociceptors to be activated, but also for the nociceptors to maintain that state of inflammation.
At the same time, the spinal cord is going to be deciding on an appropriate reaction. If the message is strong enough, it will be transported to the brain and reach the animal’s awareness, but if not, the pain will not become conscious for the animal.
The responses from the spinal cord will be:
– The activation of certain neurones of the sympathetic nervous system. If this happens, the organs that are innervated by the same segment of the spinal cord will find themselves held in a state of stress, which will modify their function. Which I find fascinating.
– The stimulation of muscle contraction in a way that helps reduce the nociceptors’ primary stimulation. Note here that the muscle contraction happens as a protective reaction, and like I said earlier, fascia isn’t only around the muscle, but around the nervous system and the instestines too. So if the pain stimulation is coming from the intestines, it will modify the musculoskeletal balance, and you will have a musculoskeletal dysfunction that is secondary to a visceral dysfunction!
If the situation doesn’t change, or if the nociceptors keep being stimulated on a regular basis, the area will enter a state of chronic inflammation. The connective tissue will then modify its structure and density to adapt to the situation and help protect the tissue. In general, the reaction is to create more collagen fibres, making the tissue more dense and less supple. This protective mechanism ensures that the body doesn’t spend too much energy on keeping muscles contracted! Very smart really.
So there you have it, 2 theories to explain how dysfunction comes in the body! I personally much prefer the second one, as I find it explains a lot more than the first one. If there’s any professionals reading this, I’d love to get your input on this!