hi this tutorial is the second in the spinal pathway series and in this video we are going to be discussing the dorsal column medeor lemniscus pathway I'll begin by clarifying that the dorsal column is sometimes called the posterior column as such this pathway is sometimes called the posterior column medior liscus pathway as we saw in the last video the dorsal column which is the ciate and grile facula collectively conveys fine touch and proprioception very quickly there are four nerve endings which may sense fine touch and these begin the pathway they are misner cor pusles pacinian cor pusles rufini endings and Merkel endings now let's talk about the pathway we'll start with two nerve endings which may have any one of those receptors we just spoke about one in the Upper Limb and one in the lower limb the cell bodies for these neurons sit in the dorsal root ganglin just outside the spinal cord we call these neurons pseudo unipolar neurons because they have an axon that runs in two directions this is in contrast with a standard unipolar neuron that has a cell body and just one axon protruding from It Anyway these neurons project from the body to the spinal cord here is a cross-section of the spinal cord and here we have our ciate and grile facula again this is known as the dorsal column the axon from the lower limb travels up through the grile fulus and the axon from the Upper Limb ascends via the CATE fulus obviously these two axons would enter the spinal cord at different levels the lower limb more quarterly and the Upper Limb more rostrally but I've shown them here in the same segment for Simplicity from the spinal cord the pathway ascends through the brain stem so here is a brain stem plus the thalamus which is not considered part of the brain stem so we have the thalamus the midbrain the ponds and the medala oblongata in the medala there are two nuclei which are the targets for the dorsal column a nucleus is a discrete collection of cell bodies within the central nervous system these two are named the CATE nucleus and the gracile nucleus and the CATE fulus and the grile fulus project to each respectively the axons of the neurons in the nuclei then continue ascending first they cross over to the other side of the brain stem this is known as a decoation here the tract is known as the internal aru fibers because in a cross-section they Arc across the brain stem then fin finally through the rest of the brain stem these fibers are known as the medial liscus finally they syapse onto a nucleus in the thalamus known as the ventral posterolateral nucleus which in turn sends projections to the post Central gyrus in the cortex the post Central gyrus is the primary sensory area of the brain so in total there are three neurons in this pathway the first is in the dorsal root gangion the second is in the ciate OR grile nucleus and the third is in the ventral posterolateral nucleus of the thalamus and that concludes this tutorial on the dorsal column medial liscus pathway in the next tutorial we'll have a look at the spinothalamic tract if you've enjoyed this tutorial please help us produce more by making a donation at www.h handwritten tutorial.com