[Music] okay so in this part of the tutorial what I'd like to do is introduce you to the idea of the different ascending and descending spinal Pathways so hopefully you will have watched the previous Parts on the spinal Pathways and we'll understand that the ascending tracks carry sensory information from the periphery to the brain and the descending tracks carry information from the brain to the periphery so what we're looking at here is a horizontal section of the cervical spinal cord and you'll recognize the H shaped gray matter in the middle and around it is the white matter and there's various different shapes that you'll see here and these represent the different ascending and descending spinal Pathways so first we'll take a look at the ascending Pathways so we'll look first at the dorsal columns which convey fine touch proception and vibration sense from the periphery up to the brain so you've got the fasiculus gillus which I've highlighted in yellow and you've got the fasiculus catus so just remember that fasiculus means small bundle so the fulus gillus carries information from the lower limb so it has ax on AXS on fibers from the lower limb whereas the fulus catus has fibers from the Upper Limb so the way I remember this is that the letter c is before the letter g in the alphabet so C is higher and your upper limbs are higher than your lower limbs so fulus catus carries fibers from the Upper Limb whereas fulus gracilis carries fibers from the lower limb now how do you remember which one is medial and which one is lateral so in yellow we've got the fasiculus gracilis and in green we've got the fasiculus catus and how to remember this is that your arms are lateral to your legs and you know from the previous pneumonic that the fulus catus carries fibbr from the Upper Limb so because your arms are lateral to your legs the fulus catus is lateral to the fulus gillus in the spinal cord so next we've got the spinothalamic tracts so these have just highlighted in blue and the spinothalamic tracts are also known as the anterolateral tracts as they sit anteriorly and laterally in the spinal cord and some texts will refer to distinct anterior and distinct lateral tracts but almost invariably there is some intermingling of fibers between the anterior and lateral tracts so on this diagram they're represented as one tract so the anterolateral tract is known as the spino thalamic tract and this relays information to theato sensory cortex regarding pain and temperature information and also crude touch so the lateral aspect of the spinothalamic tract carries pain in temperature whereas the anterior spinothalamic tract fibers carry crude touch information so the next ascending pathway is that of the spino cerebella pathways so I've highlighted these both in purple and lighter purple so you've got the dorsal and ventral spino cerebella tracts so these tracts relay information from muscle and joint receptors to the cerebellum and these tracts are examples of the pathways which carry subconsciously processed information whereas the dorsal columns the fasiculus gillus and the fulus ctis and the spinothalamic tracts carry consciously processed information which is processed in the somato sensory cortex so these spino cerebella tracts don't carry information that is consciously processed so they don't have the three neuron sequence which I described in the previous part of the tutorial so basically you've got information coming via these tracts from muscle spindles and spindles and Golgi tendon organs and this information is relayed to the cerebellum and allows for the control of posture and to coordinate muscular movements so now we'll take a look at the descending tract so these descending tracks start in the cerebral cortex and brain stem and descend down the spinal cord to innovate muscles so they are involved in controlling movement muscle tone spinal reflexes and also have um an ability to modulate some of the sensory information which is brought up via the ascending tract so essentially the ascending tra tracks bring in information from the sensory from the environment relating to sensory information and the descending tracts carry information from the center the brain to act in response to this sensory information so it's useful to think of these descending tracts as paramal or extra paramal and paramal just refers to tracks which pass through the medullary pyramids so the paramal tracts are the corticospinal tracts so you've got the lateral corticospinal tracts and the anterior corticos spinal tracts which I've highlighted in Orange so the corticospinal tracts are important to know about because they convey voluntary skilled movements originating from the motor cortices of the brain so the lateral corticos spinal tracts carry most motor information destined for the limbs and it's important in skilled voluntary movement the ventral corticos spinal tract carry axial motor information so the axial muscles are those Central muscles which aren't limb muscles essentially so you may start to notice the significance of the naming of these tracts so remember the descending tracks we talked about the spinothalamic tracts and the spino cerebella tracts you'll notice that the first part of the name of the tract relates to the first where the tract begins and the second part of the name of the tract relates to where that tract ends so spino cerebella it starts in this spinal cord and IT projects the cerebellum and then spinothalamic starts in the spinal cord projects to the thalamus so you know that they are ascending tracts and now we've just talked about the corticos spinal tract so starts in the motor cortex and projects down into the spinal cord so it's a descending tract so there's always Clues and hints in the names so just to cover some of the extra pyramidal tracts you've got the rubos spinal tract which I've highlighted in Red so this originates in the red nucleus of the midbrain tegmentum and uh is responsible for limb flexes and then you've got the tectospinal tract which I've highlighted in light purple here so it's it's seen here kind of intermingled with the medial longitudinal fasiculus but the tectospinal tract originates from the superior calculus of the midbrain so the clues in the name again so the tecto part of this word refers to the tum which consists of the superior calculus and the inferior calculus so fibers from the tectospinal tract mainly terminate in the cervical segment of the spinal cord and carry information respon responsible for movements in response to visual sensory information and then we've got the vestibular spinal tract so this is highlighted in bright pink and this originates in the vestibular nuclear in the ponds and the medulla so you've got a lateral vestibular spinal tract and a medial vestibular spinal tract so highlighted here is the in pink is the lateral vestibular spinal tract so the vestibulo spinal tract receives information from the Bony labyrinths and the cerebellum relating to balance and posture and this pathway allows for the control of extensor motor neurons in in order to maintain posture and then lastly we've got the reticul spinal tract which arises as the name suggests from the reticular formation of both the ponds and the medulla so you've got a medial or Ponto reticular spinal ract which is the one highlighted here in green and then you also have the medular reticular spinal tract which aren't shown here but I'll just draw them on the rough location of these fibers so you'd have the medular reticular spinal tract fibers in this region here so that's the lateral reticular spinal tract and this tract the reticul spinal tract is responsible for reflexes muscle tone and is also involved with the respiratory and circulatory system so that's an overview of the different ascending and descending spinal cord tracts