HISTOLOGY OF SENSORY PATHWAYS This histology practical will focus on the components of the sensory pathways For each part of the pathway we will go through the background material and then give you time to complete your practical workbook and annotate your slides in the VM Learning Objectives ➢ Introduction to using the Virtual Microscope ➢ Revise the main features of the spinal cord ➢ Identify the main histological features of the medulla ➢ Study the cortical layers of the somatosensory cortex General organisation of sensory pathways primary sensory area Cerebral cortex sensory association areas polysensory association areas 3 neuron thalamic radiation Thalamus thalamic nuclei 2 neuron lemniscus Nucleus spinal cord, cranial nerve or medulla nuclei central process (axon) 1 neuron Ganglion dorsal root or cranial nerve ganglion peripheral process (dendrite) Periphery Receptor (pain, thermal, tactile, muscle and joint receptors) Sensory pathways Carry information from skin, muscle and joint receptors to the cerebral cortex (conscious) or the cerebellum (unconscious) Conscious information travels from the spinal cord in two main systems: 1. Dorsal column medial lemniscus 2. Anterolateral systems (spinothalamic) Using the Virtual Microscope Log into the Digital slidebox: https://slidebox.bristol.ac.uk/s1167//login ◦ Neuroscience Year 1 course ◦ Introduction to Neuroscience folder ◦ Sensory pathways Open the Spinal cord, upper cervical section Annotate the slide with arrows or boxes as a practice 1. Spinal cord ▪ Primary afferent neurons convey sensory information from the periphery to the spinal cord ▪ These neurons form the dorsal root of the spinal nerves which enter into the dorsal horn ▪ Depending on the pathway the neurons will … ▪ Form the Dorsal Column Medial Lemniscus tract to the medulla ▪ Synapse in the dorsal horn onto second order neurons that will form the Anterolateral tract to the thalamus Sensory pathways at the spinal cord Gracile fasiculus Dorsal column Cuneate fasiculus Dorsal spinocerebellar (proprioception) Fasiculus proprius ventral spinocerebellar (Proprioception) Spinothalamic tract (Pain/temp) Histology of ascending & descending pathways gracile cuneate Dorsal horn Anterolateral system tracts Ventral horn 1. Spinal cord ▪ Answer the questions in your workbook ▪ Annotate your slides in the virtual microscope ▪ Ask questions and use the internet to help you Please note: the images from Tutorial 3 will also be provided after the tutorial at the end of the week 2. Medulla oblongata Second order neurons of the Dorsal Column Medial lemniscus pathway will ….. ▪ Form the arcuate fibres that decussate ▪ Project to the thalamus in the medial lemniscus ▪ Synapse onto third order neurons in the thalamus Primary afferent neurons of the Dorsal Column Medial lemniscus pathway will ….. ▪ form the gracile and cuneate fasciculi ▪ Synapse onto second order neurons in the medulla Histology of ascending & descending pathways gracile cuneate Arcuate fibres Medial lemniscus 2. Medulla oblongata ▪ Answer the questions in your workbook ▪ Annotate your slides in the virtual microscope ▪ Ask questions and use the internet to help you 3. Somatosensory cortex Third order neurons of the Dorsal Column Medial lemniscus pathway will ….. ▪ Form the thalamic radiations (somatosensory radiations) ▪ Project to the somatosensory cortex in the parietal lobe ▪ Synapse onto neurons in the somatosensory cortex 3. Somatosensory cortex Columnar organisation Histology of SENSORY (ascending) pathways SENSORY MOTOR 3. Somatosensory cortex ▪ Answer the questions in your workbook ▪ Annotate your slides in the virtual microscope ▪ Ask questions and use the internet to help you Exam Questions Your histology knowledge will be examined in the spot exam at the end of the unit Some turningpoint questions for you to try …….