7/20/2012 CourseIntroduction Review and (Preview), General Grading, Faculty,Organization Resources of the‐‐‐‐‐‐ Nervous System August 6, 2012 Grading: 6 Quizzes 20 Total 20 20 120 20 20 340 20 1 Midterm 100 220 1 Final 120 Grade % points Honors 90 306 High Pass 80 272 Pass 70 238 There will be no rounding up! 305.9999999999999999999999999999999 = a High Pass 1 7/20/2012 2 7/20/2012 Faculty: Mike Dauzvardis, Ph.D Gregory Gruener, MD, MBA John Lee, MD, Ph.D Evan Stubbs, Ph.D Lydia DonCarlos, Ph.D Jorge Asconape, MD Michael Merchut, MD And a host of neurologists, neurosurgeons, and neuropathologists assisting in the 3 small group sessions. Resources: 3 7/20/2012 Use Dr. Merchut’s handouts!!!! Since our “new book” has little clinical content, Dr. Merchut has put together his own extensive handouts relying on the old book and Netter images. Please sleep with these! Also come to the Clinical Correlation sessions given by Dr. Merchut —they are not taped. Also—use the resources on the Neuroscience Website: Labeled sections in the old lab section Self‐Quizzable sections labeled by Mike Leukam and Dauzvardis The big long practical (which I will be constantly updating) Fresh brains and models will be provided in the basement 4 7/20/2012 Have fun and learn 5 7/13/2012 Introduction and General Organization of the Nervous System Neuroscience Chapters 1,3‐‐EOTHB Michael Dauzvardis, Ph.D. Chapter 1: Introduction to the Nervous System THE BRAIN HAS SEVERAL CENTRAL AND PERIPHERAL PARTS CNS = Brain + Spinal Cord Figure 1‐1 Major components of the brain (the spinal cord has been cut off at its junction with the brainstem). A, The left side of a brain; anterior is to the left. B, The right half of a hemisected brain; anterior is to the left. C, A coronal section of a cerebrum, in the plane indicated in B. A, Amygdala; H, hypothalamus; L, lenticular nucleus; M, midbrain; Me, medulla; P, pons; T, thalamus. Downloaded from: StudentConsult (on 11 April 2012 10:17 PM) © 2005 Elsevier 1 7/13/2012 THE BRAIN HAS SEVERAL MAJOR DIVISIONS AND SUBDIVISIONS The Principal Cellular Elements of the Nervous System are Neurons and Glial Cells Node Internode Myelin Dendrites Axons Figure 1‐2 Principal components of a typical neuron. Downloaded from: StudentConsult (on 11 April 2012 10:17 PM) © 2005 Elsevier NEARLY ALL NEURONS FALL INTO ONE OF SIX CATEGORIES: 2 7/13/2012 NEURONS COME IN A VARIETY OF SIZES AND SHAPES, BUT ALL ARE VARIATIONS ON THE SAME THEME GLIA Satellite cells NEURONS Microglia Unipolar Schwann cells Pseudounipolar Oligodendrocytes bipolar Fibrous astrocytes Protoplasmic astrocytes Choroid or ependyma Figure 1‐27 Summary diagram of cell types in the nervous system, showing the distribution of glial cell types in the CNS and PNS. A layer of end‐feet of protoplasmic astrocytes (PA) forms a leaky membrane that covers the surface of the CNS, separating it from the PNS. Other end‐feet of protoplasmic astrocytes are distributed in the gray matter, abutting either neurons or capillaries (Cap). Fibrous astrocytes (FA) are interspersed among nerve fibers in the white matter, many of which are myelinated by oligodendrocytes (Ol). Small microglial cells (M) act as scavengers in response to injury, and ependymal cells (E) line the ventricular cavities (V) of the CNS. Schwann cells and their variants are the principal glial cells of the PNS, forming the myelin of peripheral nerve fibers (S1), enveloping unmyelinated axons (S2), and forming satellite cells (S3) surrounding sensory neurons in peripheral ganglia such as dorsal root ganglia (DRG) and autonomic ganglia (AG). The direction of information flow in various neurons is indicated by arrows. Processes of sensory neurons convey information to the CNS (A), in this case from skin. Information leaves the CNS to reach skeletal muscle directly (B) or to reach smooth muscle and glands (C) after a synapse in an autonomic ganglion. (Based on a drawing in Krstić RV: General biology of the mammal, Berlin, 1985, Springer‐Verlag.) Downloaded from: StudentConsult (on 11 April 2012 11:28 PM) © 2005 Elsevier Moron the Major Six Categories of Neurons: 1. Sensory 2. Motor 3. Preganglionic autonomic 4. Postganglionic autonomic 5. Local Interneurons 6. Projection Figure 1‐3 Categories of neurons in the nervous system, as seen in the spinal cord. Some neurons do not fit comfortably into one of these categories (e.g., rods and cones of the retina), but most do. 1, Sensory neurons, in this case a dorsal root ganglion cell (DRG); 2, motor neurons; 3, preganglionic autonomic neurons; 4, postganglionic autonomic neurons, with cell bodies in autonomic ganglia (AG); 5, local interneurons; 6, projection neurons. Downloaded from: StudentConsult (on 11 April 2012 10:17 PM) © 2005 Elsevier NEURONAL ORGANELLES ARE DISTRIBUTED IN A PATTERN THAT SUPPORTS NEURONAL FUNCTION Key Concepts 3 7/13/2012 MAJOR ORGANELLES OF A TYPICAL NEURON Figure 1‐4 Major organelles of a typical neuron. Downloaded from: StudentConsult (on 11 April 2012 10:17 PM) © 2005 Elsevier SCHWANN CELLS ARE THE PRINCIPAL PNS GLIAL CELLS CNS GLIAL CELLS INCLUDE OLIGODENDROCYTES, ASTROCYTES, EPENDYMAL CELLS, AND MICROGLIA SCHWANN CELLS FLATTEN OUT AND BECOME SATELLITE CELLS AS THEY SURROUND A DORSAL ROOT GANGLION Figure 1‐22 Schwann cells flattened out as satellite cells (Sa) surrounding a single dorsal root ganglion cell from a rat. The actual size of the cell is about 20 × 30 μm. The inset at the lower left is a light micrograph of part of a dorsal root ganglion in which the nuclei (arrows) can be seen in flattened satellite cells surrounding individual, much larger dorsal root ganglion cells (arrowhead). (Electron micrograph, from Pannese E: Neurocytology: fine structure of neurons, nerve processes, and neuroglial cells, New York, 1994, Thieme Medical Publishers. Inset, courtesy Dr. Nathaniel T. McMullen, University of Arizona College of Medicine.) Downloaded from: StudentConsult (on 11 April 2012 11:28 PM) © 2005 Elsevier 4 7/13/2012 NINE UNMYELINATED AXONS IN THE DORSAL ROOT ALL SURROUNDED BY A SINGLE SCHWANN CELL Figure 1‐26 Unmyelinated nerve fibers in a dorsal root of a rat. Nine axons, each with the usual complement of microtubules, neurofilaments, and mitochondria, are embedded in a single Schwann cell (S). Even though no myelin is present, seven of the axons are almost completely ensheathed, communicating with the adjacent extracellular spaces only through small clefts (arrows) in the Schwann cell wrapping. The other two axons (*) are partially exposed at the surface of the Schwann cell. (From Pannese E: Neurocytology: fine structure of neurons, nerve processes, and neuroglial cells, New York, 1994, Thieme Medical Publishers.) Downloaded from: StudentConsult (on 13 April 2012 03:23 PM) © 2005 Elsevier MYELINATION IN THE PNS; THE SCHWANN CELL Figure 1‐24 Schematic diagram of the formation of myelin in the PNS. A, A single Schwann cell forms an internode, unrolled from the axon it would normally be wrapped around. The cell is flattened into a two‐membrane‐thick sheet, with cytoplasm (c) remaining only as a thin rim around the periphery and as a few thin fingers extending between the membranes. B, Longitudinal section through the internode resulting from the Schwann cell in A spiraling around the axon. Most of the internode consists of tightly wrapped Schwann cell membranes. Some cytoplasm remains on the surface of the internode near the nucleus, as small pockets near the node, and as Schmidt‐Lanterman incisures. (Redrawn from Krstić RV: Illustrated encyclopedia of human histology, Berlin, 1984, Springer‐Verlag.) Downloaded from: StudentConsult (on 11 April 2012 11:28 PM) © 2005 Elsevier NODES AND INTERNODES Figure 1‐23 Myelin sheaths and nodes of Ranvier in peripheral nerve fibers. A fixed peripheral nerve was teased apart into individual nerve fibers and stained with osmium (a lipophilic stain for membranes). The axon is the central pale area in each fiber, and the myelin sheath stands out on both sides of each axon as a more densely stained area; a few nodes of Ranvier (arrowheads) are visible. The occasional diagonal clefts (arrows) that appear to cross the myelin sheaths are known as Schmidt‐Lanterman incisures; they correspond to thin extensions of Schwann cell cytoplasm that spiral around with the myelinating membranes (see Fig. 1‐24). (Courtesy Dr. Nathaniel T. McMullen, University of Arizona College of Medicine.) Downloaded from: StudentConsult (on 13 April 2012 03:23 PM) © 2005 Elsevier 5 7/13/2012 MYELINATION IN THE CNS: THE OLIGODENDROCYTE Figure 1‐30 Schematic diagram of the formation of myelin in the CNS. A series of processes (p) emanate from an oligodendrocyte, each one giving rise to a flattened expansion that wraps around an axon to form an internode. As in the case of myelin in the PNS (see Fig. 1‐24), most of the internode consists of tightly wrapped membranes, but small rims and fingers of oligodendrocyte cytoplasm (c) are also carried along. (Redrawn from Krstić RV: Illustrated encyclopedia of human histology, Berlin, 1984, Springer‐Verlag.) Downloaded from: StudentConsult (on 11 April 2012 11:28 PM) © 2005 Elsevier ONE BIG OLIGO Figure 1‐31 A single oligodendrocyte (OL) in the spinal cord white matter of a young rat, myelinating two different axons (A1, A2). This cell and its processes stand out because in young rats, like many other young mammals, myelin has not yet developed around many axons. Note that the oligodendrocyte is connected to its myelin sheaths by thin processes; this tenuous connection has been cited as a possible reason for the paucity of remyelination after injury to myelin sheaths in the brain and spinal cord. Scale mark equals 2 μm. (From Waxman SG, Sims TJ: Brain Res 292:179, 1984.) Downloaded from: StudentConsult (on 11 April 2012 11:28 PM) © 2005 Elsevier ANSWER ME THIS! 6 7/13/2012 ANSWERS 1‐b 2‐a 3‐c 4‐b 5‐a 6‐e 7‐f 8‐c 9‐b 10‐f 11‐e 12‐c 13‐g 14‐b Chapter 3 Gross anatomy and General Organization of the Central nervous System The Long Axis of the CNS Bends at The Cephalic Flexure Figure 3‐1 Directions in the CNS.