Day 192: Know your spinal cord – The Tectospinal tract
Welcome to day thirty-five in the know your spinal cord series! For the new people, we have a whole neuroanatomy category dedicated to these posts! For everyone else (or those of you just interested in today’s topic, this is going to be on another smaller tract of the spinal cord we haven’t covered yet. Today we are talking about the tectospinal tract, not to be confused with the spinotectal tract, so let’s get started.
Yesterday we covered the vestibulospinal tract, a small but mighty tract that helps us keep our balance and our head level. This tract assists in that function as well. The spinotectal tract (also known as the colliculospinal tract) coordinates head and eye movements and works in parallel to the vestibulospinal tract. This tract is also part of the extrapyramidal system, which is defined as part of the motor system that mediates involuntary actions. This is distinct from the pyramidal system in that it does not involve the motor cortex, but the extrapyramidal system gets its name because the tracts do not travel through the medullary pyramids.
Because we are talking about such a small tract, it often gets labeled in somewhat different places. Frankly this could be for a lot of reasons, but if I had to guess, I would say this is due to the simplification of the tracts. For example, the image below we have labeled the approximate location of the tectospinal tract, however the size and shape of the the tract in the photo is not absolutely correct. That area is actually home to more than just one tract (namely the anterior corticospinal tract). So we do our best, but just know we have highlighted (roughly) the area of the tract and that there are images with it labeled in a slightly different location.
As we mentioned before, the function of the tectospinal tract is to mediate reflex postural movements of the head in response to visual and auditory stimuli. It originates (as the name of the tract implies) at the midbrain tectum (latin for roof) it is literally the top (roof) of the fourth ventricle, below is an image showing the tectum in relation to other landmarks of the midbrain. The tectum is involved in reflexes in response to visual or auditory stimuli.
It is responsible for motor impulses that arise from one side of the midbrain to muscles on the opposite side of the body (contralateral). The tract descends to the cervical spinal cord to terminate in Rexed laminae VI, VII, and VIII to coordinate head, neck, and eye movements, primarily in response to visual stimuli. The Tectospinal tract receives information from the retina and cortical visual association areas. In response to visual stimuli, the tectospinal tract mediates reflex movements. It is able to orientate the head/trunk towards auditory stimuli or visual stimuli.
This of course is easily confused with the spinotectal tract, this isn’t the first confusing tract name we’ve come across either. The difference here is the spinotectal tract is actually thought to exist. In fact, we are fairly certain this is a thing and it originates in the spinal cord (again, as the name implies) and terminates at the midbrain, making this an afferent tract unlike the tectospinal tract which is efferent. This tract is thought to be involved in some aspect of pain perception, although we aren’t totally sure! That’s kind of weird, right?
That is the basics of the tectospinal tract (and even the bonus spinotectal tract). We may have to start talking more about the state of research now that we’ve pretty much covered the basics. We did manage thirty-five days of spinal info, so that isn’t too bad. I’m not quite sure what will happen tomorrow since I am juggling quite a bit of other writing duties now, but I’ll figure something out.
Until next time, don’t stop learning!