Week One Notes: Structure of the Spinal Cord and Terms (1/12/16-1/14/16)
Week One Notes: Structure of the Spinal Cord and Terms (1/12/16-1/14/16) Neuro 3050
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NEUROSC 3000 - 020
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This 5 page Class Notes was uploaded by alvey.15 Notetaker on Monday January 18, 2016. The Class Notes belongs to Neuro 3050 at Ohio State University taught by Georgia Bishop in Spring 2016. Since its upload, it has received 176 views. For similar materials see Structure and Function of the Nervous System in Neuroscience at Ohio State University.
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Date Created: 01/18/16
Structure and Function Neuroscience Notes: Structure and Function of the Spinal Cord and Terms 1/12/2016 - 1/14/2016, Spring Semester, Dr. Bishop’s class. Notes by Alexandra Alvey. Anatomical Orientation Terms Looking at the brain: Dorsal(anterior)-imagine a dolphin’s dorsal fin on the top of your head. Towards the parietal lobe. Ventral(posterior)- Latin for “belly” the belly of your brain! Towards the Temporal lobe Rostral- towards the frontal lobes Caudal- Latin for “tail” towards the occipital lobe Looking at the spinal cord: Dorsal(anterior)- imagine a dolphin’s fin on a dolphin’s back or your back. Ventral (posterior)- literally towards your belly Rostral- R for rising towards the brain Caudal- C for climbing down towards the feet Sagittal view- S for side view of the brain or side cut. Splits the brain in in to left and right hemispheres. Coronal view- like coronation of a queen. The crown is placed on the head like the cut is made on the crown of the head. Horizontal view- splitting the brain in to top and bottom. Meninges Dura mater is Latin for hard mother. It is the first layer just under the skull and around the spinal cord. The dura mater is clearly visible when the skull is removed and looks like leather because it is made of dense connective tissue. The arachnoid layer is smooth where it attaches to the dura mater and a layer of meshwork (arachnoid trabeculae) continuing down towards the pia mater. The space between the arachnoid and pia mater is called the subarachnoid space and is filled with cerebrospinal fluid (CSF). The arachnoid membrane and subarachnoid space also continues around the spinal cord. CSF provides cushioning for the brain and spinal cord. Pia mater is Latin for soft mother. The pia mater is the thinnest layer of the meninges and contours around the brain and spinal cord. This layer is not distinguishable when the dura mater and arachnoid layer are removed because it is so closely attached to the brain and spinal cord. The dura mater, arachnoid, and pia mater stop at the coccyx level of the spinal cord. Vertebral Column You do not need to memorize the number of vertebrae in the vertebral column but if it helps for further studying there are seven cervical vertebrae (C1-C7), twelve thoracic vertebrae (T1-T12), five lumbar vertebrae (L1-L5), five sacral which are fused together (S1-S5), and three coccygeal vertebrae which are fused together (Co1-Co3) Need to know the spinous process, transverse processes, lamina and body of the vertebrae at the least and identify them on a picture. Reference slide 3 for a picture of the vertebrae. The spinous process on a vertebra is medial (in the middle) of bilateral transverse processes (two processes to the side). The spinous process and transverse processes face dorsal (towards the back) of the body. The body of the vertebrae face ventral (towards the front) of the body. The lamina is the bridge of bone that holds the two transverse processes and the spinous process together. A laminectomy is when a surgeon makes bilateral incisions of the lamina proximal to the transverse processes so that they can remove the dorsal vertebrae to gain access to the spinal cord. The vertebrae are stacked on top of each other. Between every two vertebrae is the intervertebral foramen where the peripheral nerves emerge. Inter means between and when coupled with vertebral the term means “between vertebrae”. Spinal Cord Development The neural tube consists of three layers the endoderm, ectoderm, and mesoderm. The ectoderm will become the brain and spinal cord. The mesoderm will become the skin, muscle, and bone. When the neural tube closes to form the beginnings of the spinal cord and brain the mesoderm separates in to somites but maintains contact with the adjacent areas of the ectoderm. In a fully developed human this results in bands of skin, muscle, and sometimes bone having dermatomes or areas of the body that are innervated by specific nerves in the spinal cord. Dermatomes are most apparent on the trunk of the body. Shingles is an infection of the dorsal root (sensory nerve) supplying a specific area to the body. The pattern of shingles on the patient matches the dermatome precisely and can be mapped back to the dorsal nerve infected. Reference slide 10 for diagrams associated 8 weeks of life- the spinal cord fills the vertebral canal and all three levels of the meninges are anchored at the coccyx. Each dorsal nerve is emerging from their respective vertebral foramen and will stay here throughout development. 24 weeks of life- the vertebral column continues to grow but the spinal cord does not. Spinal cord ends around the first sacral vertebrae. Sensory fibers have established connections in the periphery and dorsal and ventral nerves elongate as the vertebral column continues to grow. Birth- spinal cord ends in lumbar region and nerves elongate. Adult- cord ends in L2 and L3 generally The most important aspect to remember is that dorsal and ventral nerves establish their connections in the vertebral canal at 8 weeks and elongate as the vertebral canal continues to grow. The nerves do not move to different vertebral foramen as the vertebral canal grows! Specialization of the Pia Mater Reference slides 9 and 11 If you were to cut open the meningeal layers to expose the spinal cord you would be able to visibly see the dura and arachnoid layer. The arachnoid trabeculae would not be visible because they are a fine filament that are only visible when the subarachnoid space is filled with CSF. The pia mater is only visible bilaterally (on both sides) to the exposed spinal cord at the denticulate ligament. The denticulate ligament connects all the way to the inner layer of the dura mater down the entire spinal cord. The function of the denticulate ligament is suspension of the spinal cord along with the dura mater and arachnoid. Anatomy of Spinal Cord The spinal cord ends at the conus medullaris around L2-L3 but the pia continues to grow. Remember the pia is a thin layer contouring with the spinal cord so as the pia continues to grow it fills with CSF rather than spinal cord. This layer of the pia that continues to grow is called the filum terminalae and the CSF filled space that starts at L4 and extends to S2 is called the lumbar cistern. The lumbar cistern is the area where it is safe to receive a lumbar puncture because there is less risk of puncturing the spinal cord. Nerve roots continue to grow towards their respective intervertebral foramen past the conus medullaris (end of the spinal cord) and project in to the lumbar cistern. This collection of nerve roots forms the cauda equina or Latin for “horses tail” because it looks like one. The cervical nerves of the spine emerge at the vertebral foramen above the same numbered vertebrae. Example) C2 spinal nerve comes out of the vertebral foramen made by C1 and C2 The lumbar, sacral and coccygeal nerves of the spine emerge at the vertebral foramen below their respective vertebrae. Example) T2 spinal nerve comes out of the vertebral foramen made by T2 and T3. Organization and Function of the Spinal Cord Reference slides 18-35 for images If a horizontal cut is made through the spinal cord, we would not be able to tell the neurons and the axons a part from one another. A Nissl stain stains the neuronal bodies in the butterfly shaped region of gray matter in the center of the spinal cord. A silver fiber stain stains the axonal tracts or white matter that surround the gray matter. If you imagine a coronal line dividing the spinal cord in to a ventral and dorsal side it makes the anatomy and function of the spinal cord easier to understand. The ventral side of the spinal cord consists of two ventral horns of gray matter (neurons and glia) and two ventral columns of white matter (axons and glia). The ventral side of the spinal cord has nerves that carry motor information to the muscles, skin, and organs. On the dorsal side of the spinal cord are the two dorsal gray horns (neurons and glia) and two dorsal white columns (axons and glia). The dorsal side of the spinal cord receives sensory input from the skin, organs, and muscles. There are also two lateral gray horns and two lateral white columns which are responsible for autonomic responses (fight or flight response). A distinguishing feature of the ventral spinal cord is anterior median fissure that runs longitudinally along the spinal cord. On the dorsal (or posterior) side of the spinal cord is the posterior median sulcus. A fissure is a deeper groove than a sulcus thus it is easy to determine the ventral (or anterior) side of the spinal cord. Ganglion- a collection of neurons in the peripheral nervous system (anything outside the spine and brain) Tract- axonal pathways connecting two regions in the CNS. A tract is composed of independent fibers that serve a common function=fasciculus Tract= fasciculus Funiculus- a collection of axonal tracts. More axonal tracts are FUN!!! A collection of fasciculi is called a funiculus. The lateral, dorsal, and ventral white columns that make up the spinal cord are funiculi. The dorsal funiculus receives sensory input from the dorsal root ganglion in the intervertebral foramen. The dorsal funiculus is a combination of ascending tracts that send sensory information to the brain. The ventral funiculus sends motor information to the ventral root and out towards the periphery. This would not be a descending tract because the ventral funiculus is sending information to the peripheral nervous system (PNS) and not the CNS. An example of a descending tract would be from the motor cortex in the frontal lobe to the ventral horn of the spine. This would be called a corticospinal tract because it is traveling from the cortex to the spine. Remember that dorsal root and ventral root axons combine in the intervertebral foramen to form a nerve that innervates the same area in the periphery. The anterior white commissure is located dorsal or anterior to the anterior median fissure. The axons that make up this structure cross to both sides of the spinal cord (right and left areas) to coordinate movement. The left cortex is in control of the right side of the body and the right cortex is control of the left side of the body.
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