hi everybody dr. Mike here in this video I want to talk to you about how our brain controls motor movement or activities now in one of my previous videos I spoke to you about if we were to do a transverse section for the spinal cord and look into the spinal cord bird's-eye view you see a couple of important anatomical structures first of all I said you see all this what we call gray matter deep inside the spinal cord this gray matter is where one year on speaks to the next neuron this is where information is integrated in stats that make sense now on the outside we've got what we call white matter and they are simply pathways or tracks they're the highways in which electrical signals or neurons take now if they're going up to the brain it's going to be sensory information if they're going down and away from the brain it's going to be motor information now in the previous video I spoke to about sensory information that's this side all the information going up to the brain different types now I want to talk to you about motor information coming down from the brain now first thing I want you to see is that you've got pyramidal or extra pyramidal signals coming from the brain what's the difference now pyramidal is this direct signal to specific muscles or muscle groups and it's going to be four predominately conscious movement if we look at extrapyramidal if they're going to be indirect pathways and they're more so for unconscious movement they also finely tune conscious movement now if we look at the pyramidal system these are going to be information coming from the brain for conscious movement and they're both called the corticospinal tracts again they're just the highways Claude echoes refer to the cortex so that means it's coming from the motor cortex if any signal is going to the cortex or coming from the cortex you're going to be consciously aware of it so the lateral and ventral or anterior corticospinal tracts are for conscious motor movement now the lateral corticospinal tract which you can see here this is going to be coming from the motor cortex which is in the precentral gyrus of the frontal lobe okay I'm going to do a separate video on that so don't stress out if I want to move my right arm to draw all right so fine motor movement predominately of my limbs this is going to be the signal for the lateral corticospinal tract if I want to move my right arm it's going to come from my left motor core-tex so it's coming from up here it's going to descend down it's going to cross to the other side Crossing is called decussation and that happens at the medulla that's the lowest part of the brainstem midbrain pons medulla crosses over at the medulla continues down and via this lateral corticospinal tract and then when it's at the level in which it needs to go to my hand to tell it to move alright it jumps down through this grey matter here could the virtual grey horn and jumps out and goes to my arm for riding so that again is fine motor control that is the lateral corticospinal tract the ventral corticospinal tract is not for final movement of the limbs but it's predominately for movement of the trunk and another difference here is that it's actually going to descend down the brainstem and spinal cord down the same side of the brain in which it came down from so it's going down down down down down down down now remember ventral corticospinal tracts here it's going down the same side now when it needs to innervate a part of my trunk that needs to move at the level in which it exits that's where it's going to cross over again to the ventral grey horn and come out and innovate the trunk to move now another thing that you can see is that it's quite small and it also basically stops at the mid thoracic area so if you kept doing these transverse sections down the spinal cord you'd find that the ventral or anterior corticospinal tract is gone by the time you descend down further to from the mid thoracic area okay what about these extrapyramidal tracts firstly the rubra spinal tract which you can see here is very close to that a lateral corticospinal tract and they play a similar role fine motor movement predominately of the limbs now we know that it's on two limbs because two reasons one as we cut down the the spinal cord by the time we get to the cervical region the rubra spinal tract basically disappears that's one indication that just controls the limbs another indication is that if you a blade or put a lesion in this particular area of animals specifically primates you find that they don't have fine motor control of their upper limbs decreased flexion and gripping seems to disappear so we think that we've evolved this rubra spinal tract to be able to climb as we go to the reticulospinal tract which you can see here and the vestibular spinal tract I'll group them together they're there for posture balanced coordinated movement okay so it plays an important role in coming from our vestibular system so this is going to be in the ear balance head movement head position and also posture and coordinated movement both of these together then the tech toe spinal track is again is important for head movement and I moment but also as a reflexive response to visual or auditory cues so if you may hear something and your head it reflexively moves towards it or you see something in your eyes dart in that direction that's going to be in part responsible due to detecto spinal tract so this is a quick overview of motor or descending pathways coming from the brain going down the spinal cord