Extrapyramidal Motor Pathways
Channel: About Medicine
Date: 2018-10-03

The bundles of axons responsible for transmitting subconscious motor impulses are the extrapyramidal tracts. We'll go through the vestibulospinal, reticulospinal and tectospinal tracts in this video.

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A nucleus is a discrete chunk of grey matter, and grey matter is the cell bodies of neurons. 

These cell bodies receive information from neurons that are coming from the inner ear.
They're transmitting info about the head's position in space, from the semicircular canals, through the vestibular nerve.

Having dropped that info here, this neuron's axon heads down in a tract known as the vestibulospinal tract. 

Descending just posterior to the pyramids of the medulla, the axon then fires on the cell body of a lower motor neuron in the anterior horn of the grey matter. 

So that’s the vestibulospinal tract.

It receives info about the head's position and conveys it to muscles of the head and upper limbs, which can adjust our positioning if required.

The reticulospinal tract's up next, for which we will bring this in, the reticular formation. The reticular formation is composed of many nuclei, and spans the medulla to the midbrain. 

Their cell bodies in here, our axons descend in a collection known as the reticulospinal tract. They drop their information on cell bodies, again in the anterior horn, of neurons which head out to muscles in the torso and upper limb. 

The purpose of these messages are to maintain our posture, especially while we’re in motion. 


The tectospinal tract begins in the tectum, which is this part of the pons. The whole back part of the pons is the tectum. 

Now, within the tectum we have these little mounds of grey matter, called colliculi - Latin for ‘mound’ - we have superior colliculi and inferior colliculi. 

The superior colliculus receives visual info, the inferior colliculus, auditory. 
If we see bright, sudden movement, or hear loud, sudden noises - this information is passed down the tectospinal tract to activate muscles of the head, neck, and upper limbs. 

Any sudden movement in response to something you weren’t expecting to see or hear is the work of the tectospinal tract.

In learning neuroanatomy, we can all agree that the language used to describe its components is a hurdle to understanding. There’s a huge amount of new words to learn, but the fact is that the content itself is very simple. You just have to look harder sometimes, to find that simplicity.