Neuroanatomy: An Illustrated Colour Text - Chapter 1 PDF

COMMONWEALTH OF AUSTRALIA WARNING This material has been reproduced and communicated to you by or on behalf of University of Tasmania in accordance with section 113P of the Copyright Act 1968 (Act). The material in this communication may be subject to copyright under the Ac...

COMMONWEALTH OF AUSTRALIA WARNING This material has been reproduced and communicated to you by or on behalf of University of Tasmania in accordance with section 113P of the Copyright Act 1968 (Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice Course of Study: (CXA740) Neurological Physiotherapy Title of work: Neuroanatomy; an illustrated colour text, Sixth edition. (2020) Section: Chapter 1. Introduction and overview pp. 1--31 Author/editor of work: Crossman, A. R.; Neary, David; Crossman, Ben Author of section: A. R. Crossman; David Neary; Ben Crossman Name of Publisher: Elsevier Neuroanatomy AN ILLUSTRATED COLOUR TEXT Neuroanatomy AN ILLUSTRATED COLOUR TEXT Sixth Edition Alan R Crossman PhD DSo Emeritus Professor of Anatomy The University of Manchester Manchester, UK David Neary MD FRCP Honorary Professor of Neuroscience Manchester, UK Illustrated by Ben Crossman MA For additional online content visit StudentConsult.com ELSEVIER ELSEVIER © 2020, Elsevier Limited. All rights reserved. Fifth edition ® Elsevier Limited 2015 Fourth edition © Elsevier Limited 2010 Third edition © Elsevier Limited 2005 Second edition ® Elsevier Limited 2000 First edition © Pearson Professional Limited 1995 The right of Alan Crossman and David Neary to be identified as authors of this work has been asserted by them in accordance with the Copyright, Designs and Patents Act 1988. 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[NEIN] y·vr source for books, IL:IS2EX&LE?] journals and multimedia Lh....ill in the health sciences www.elsevierhealth.com The Working together publisher's policy is to use "Lo Book Aid International to grow libraries in developing countries paper manufactured from sustainable forests www.elsevier.com www.bookaid.org I Printed in China Last digit is the print number: 9 8 7 6 5 4 3 2 1 UNSW APR 0 + 2022 Senior Content Strategist: Jeremy Bowes Senior Content Development Specialist: Kim Benson Project Manager: Julie Taylor LIBRARY Design: Brian Salisbury Illustrator: Ben Crossman Marketing Manager: Deborah Watkins Preface to the sixth edition A basic knowledge of human Although the question "What do I need to The internal anatomy of the central neuroanatomy is an essential prerequisite know?" is anathema to some educators, it nervous system - its nuclei, nerve fibre for medical students about to embark is perfectly understandable. What to tracts and, particularly, their connections upon clinical studies. Without such include and what to leave out is, of course, - cannot always be readily visualised in knowledge it is impossible to understand a matter of judgement. Our approach has dissections, brain sections or scans. As a the myriad of clinical signs and symptoms been to include what we consider to be consequence, clear, uncomplicated and that arise from disorders of the nervous essential material, correlating, wherever explicit illustrations are an absolute system. This book has been designed possible, anatomical structure with necessity. The illustrations have always primarily for medical students, but function and, where applicable, relating it been a strong point of the book - and one neuroanatomy is an important subject also to clinical significance. We believe that the of the features that has attracted most for students of basic neuroscience and of breadth and depth of coverage of the compliments from readers. Since the third many subjects allied to medicine. subject in Neuroanatomy are sufficient to edition, Ben Crossman has been In revising and updating Neuroanatomy enable students to commence their responsible for illustration of the entire for a sixth edition, we have retained our training in clinical neuroscience with book. For this edition, some new figures original intention to produce a relevant, confidence. have been introduced and virtually all of clear, succinct and well-illustrated account Clarity is also of great importance. the figures have been revised to further of the anatomy of the human nervous Neuroanatomy is a complex subject and improve clarity and aesthetic appearance. system. one with which students often find We are grateful to Ben for his artistic Relevance is, perhaps, the most difficulty. We have made every effort, interpretation of our primitive sketches important feature. Neuroanatomy is an therefore, to avoid vagueness, opacity and and his skillful enhancement and extensive subject, and the pace of research ambiguity and to make descriptions and annotation of the photographs of in both the basic and clinical sciences concepts as straightforward as possible. anatomical specimens. means that it is ever-expanding. At the Not only does Neuroanatomy focus same time, students are under pressure and on the essential material but the text AR Crossman neuroanatomy will almost certainly not be is also deliberately succinct and to the D Neary the only subject that they are studying. point. Manchester 2018 Preface to the first edition This book has been written primarily for recommended the development of a nervous system and its disorders. The aim undergraduate medical students. At the system-based core curriculum and has of this book, therefore, is to provide a clear same time, we have borne in mind emphasised the crucial importance of and concise account of the anatomy of the students following other health science integration between basic science and human nervous system in sufficient detail courses where a basic understanding of the clinical medicine. These proposals have to understand its main functions and the nervous system and its major disorders is been welcomed and amplified, with common disorders by which it is affected. required, and also students of basic respect to the teaching of neurology, by the An important feature of the book is the neuroscience, who are invariably intrigued Association of British Neurologists. integration of neuroanatomy with and edified by discussion of the disorders No area of medical science lends itself illustrative clinical material. This has been which afflict the human nervous system. better than neuroscience to such a done in order to show how a knowledge The book has been prepared during a system-based, integrated approach and this of neuroanatomy can help in the period of widespread debate on, and has been the principal philosophy guiding understanding of clinical symptoms and evolution in, the substance and style of the preparation of this book. Neuroscience, also to emphasise those areas of medical education. There are several with all its sub-specialities both basic and neuroanatomy which are particularly driving forces for change, one being the clinical, is an enormous field where the relevant to human neurological disease. recognition that unreasonable and growth of knowledge through research is We have introduced clinical concepts in unnecessary demands are often being exponential. This creates a great challenge the most elementary way to give a broad made of students in the sheer volume of to the medical educator in selecting what outline of the aetiology of nervous disease information which they are required to should comprise the core curriculum. It and the link with clinical diagnostic assimilate. This has prompted students, also signifies the potential for future methods. Clinical material has been educators and health professionals alike to advances in the diagnosis, prevention and integrated as closely as possible with the question, across the whole curriculum, the treatment of neurological disease, relevant neuroanatomy. Furthermore, the depth of knowledge which is required by recognised by the designation of the 1990s clinical text has been boxed so that it is the newly-qualified doctor and the means as the 'Decade of the Brain'. readily identifiable and can be easily by which it should be achieved. The Neuroanatomy is the cornerstone upon selected to review or pass over. Each General Medical Council has which is built an understanding of the chapter also contains boxed summaries. Contents Assessment (including Problem-solving) www.studentconsult.com 1 Introduction and overview 1 2 Cells of the nervous system 32 3 Peripheral nervous system 36 4 Autonomic nervous system 46 5 Coverings of the central nervous system 50 6 Ventricular system 55 7 Vasculature of the central nervous system 60 8 Spinal cord 68 9 Brainstem 89 10 Cranial nerves and cranial nerve nuclei 99 11 Cerebellum 113 12 Thalamus 120 13 Cerebral hemisphere and cerebral cortex 127 14 Basal ganglia 142 15 Visual system 150 16 Hypothalamus, limbic system and olfactory system 154 Glossary 164 Index 167  Introduction and overview 1 Neuroanatomical terminology and Grey and white matter, nuclei and tracts 4 Major sensory pathways 20 conventions 2 Decussation of sensory and motor Major motor pathways 21 Components and organisation of the pathways 4 Basic clinical diagnostic principles 23 nervous system 2 Development of the central nervous Aetiology of neurological disease 23 Neurones and neuroglia 2 system 5 Time-course of disease 26 Central and peripheral nervous systems 3 Overview of the anatomy of the central Site of the lesion and clinical Somatic and autonomic nervous nervous system 11 syndromes 26 systems 3 Coverings and blood supply 11 Investigation of neuromuscular Afferent neurones, efferent neurones and Anatomy of the spinal cord 13 disease 30. interneurones 4 Anatomy of the brain 14 The nervous system of all animals functions to detect changes in the process, the human nervous system is the most complex and internal and external environments and to bring about responses in versatile product of evolution. muscles, organs and glands that are appropriate for the preservation Although a great deal is known about how the nervous system of the individual and the propagation of the species. In relatively works, much still awaits elucidation. Indeed, the anatomical, primitive species such functions are focused primarily on: physiological, biochemical and molecular basis of neural function remain areas of intense research activity in both the basic and Maintenance of the internal environment (homoeostasis) clinical sciences. Perception of, and response to, external stimuli/threats The nervous system can be damaged by inherited and Finding food developmental abnormalities, by disease and traumatic injury and Mating by neurodegenerative processes associated with ageing. The With ascent of the evolutionary scale there is, in addition, an prevention, diagnosis and treatment of neurological disorders are, increasing capacity for 'higher functions' of the nervous system, therefore, of immense socio-economic importance. A knowledge such as learning, memory, cognition and, ultimately, of neuroanatomy and its correlation with function and self-awareness, intellect and personality. At the pinnacle of this dysfunction is fundamental to the practice of clinical (Para)sagittal or (para)median plane Coronal or frontal plane Medial - - ~ Posterior Lateral ◄- - - - - ► ◄ Anterior & ·="" --r--~ - ·-~~~-,~ -~-----► Lateral -1, ' e ----- ", ' \ '' I Transverse, horizontal or axial plane Superior > 7 Y Inferior Fig. 1.1 Neuroanatomical terminology for planes, directions and relationships. 2 NEUROANATOMY Anterior Dorsal Cruscerebri '%3 Superior colliculus 2e, "1 Ventral Posterior Fig. 1.2 (A) Transverse histological section of the midbrain in the conventional neuroanatomical orientation and (B) corresponding axial MRI scan in conventional neuroradiological orientation. neurosciences and to the prospect of future advances in the customary to use the terms that are common to all anatomy when prevention and treatment of neurological disorders. describing a position in space and to reserve the terms 'rostral, caudal, dorsal and ventral' for the description of location and Neuroanatomical terminology and direction relative to the long axis of the nervous system. conventions In neuroanatomy, horizontal or transverse sections through the spinal cord and lower part of the brain (brainstem) are usually The formal names given to parts of the body are agreed depicted/orientated with dorsal at the top and ventral at the internationally by the Federative Committee on Anatomical bottom (Fig. 1.2A). The convention in clinical neuroradiology, on Terminology and have been published as the Terminologia the other hand, is that axial images are orientated as if looking Anatomica (1998; Thieme). The names of many structures in the from the subject's feet towards the head, with anterior at the top nervous system have a Greek or Latin origin and are unique to of the image. In sections that contain the brainstem, therefore, the neuroanatomy. Often the name is descriptive of some perceived dorsal aspect of the brainstem is towards the bottom of the image physical characteristic, such as shape (e.g. 'hippocampus', meaning and the ventral aspect is towards the top (Fig. 1.2B). This sea-horse) or colour (e.g. 'substantia nigra', meaning black convention means that left and right are also reversed. substance). Some structures are known by eponyms, usually in recognition of the person who first described them or whose work Components and organisation of the on them was particularly prominent (e.g. circle of Willis; fora men nervous system of Monro). Many of the latter names are considered to be anachronistic, but some remain in common usage. Neurones and neuroglia In anatomy generally, the location and relationships of The basic structural and functional unit of the nervous system is structures are described with reference to three orthogonal planes: the nerve cell or neurone (Figs 1.3, 1.4), of which the human sagittal or median, horizontal or transverse ( called axial in nervous system is estimated to contain about 10. The functions radiology) and coronal or frontal (Fig. 1. 1 ). Directions and of the neurone are to receive and integrate incoming information relationships are designated as medial or lateral, superior or from sensory receptors and other neurones and to transmit inferior and anterior or posterior, with reference to the orientation information to other neurones or non-neural structures that are of these planes. There is, however, an additional terminological under neural control (muscles, organs and glands - sometimes complication when describing the brain and spinal cord, as referred to as 'effector organs'). Neuronal structure is highly explained below. specialised to fulfil these functions. Each neurone is a separate In neuroanatomy, the positional/directional terms - rostral, physical entity with a limiting cell membrane. Information is caudal, dorsal and ventral- are also commonly used. These terms passed between neurones at specialised regions called synapses have their origin in embryology and mean, respectively, towards where the membranes of adjacent cells are in close apposition the head end (rostral), tail end (caudal), back (dorsal) and belly (Fig. 1.3). (ventral). If the long axis of the brain and spinal cord were to There is wide diversity in the size and shape of neurones in remain in a straight line during embryological development then, different parts of the nervous system, but all share certain in the adult, rostral would simply equate to superior, caudal to common characteristics. There is a single cell body from which a inferior, dorsal to posterior and ventral to anterior. For all intents variable number of branching processes emerge. Most of these and purposes, this is what happens with the spinal cord but the processes are receptive in function and are known as dendrites. long axis of the brain, on the other hand, undergoes considerable The dendrites possess synapses, sometimes many thousands of distortion and, in particular, the brainstem becomes flexed at them, through which they receive incoming information from several points (see Fig. 1.12). In neuroanatomy, therefore, it is other nerve cells. In sensory neurones, the dendrites may be  Chapter 1 Introduction and overview 3 Dendrites ------Dendrite ---------Cell body Cell body O~L ;-:-~''"' " ""' [AX()[\ Myelin ·ii Terminal DOutOn Nodeof_-----------11} 20um Rawer [l] Presynaptic Fig. 1.4 Pseudocoloured three-dimensional reconstruction of a ending neurone from the hippocampus, imaged by confocal laser scanning microscopy. One of the processes at the base of the neurone is the axon. (Courtesy of Or RA McKinney, Brain Research Institute, University of Zurich, Switzerland.) , » > Synaptic ]> vesicles '/ saw diffuses across the narrow gap between pre- and postsynaptic membranes and binds to specific receptors on the postsynaptic ~ gap(cleft) cell, inducing changes in the membrane potential. The change Postsynaptic may be either to depolarise the membrane, thus moving towards cell the threshold for production of action potentials, or to Fig. 1.3 Schematic representation of the basic structure of the hyperpolarise and, thus, stabilise the cell. neurone and the synapse. The other major cellular components of the nervous system are neuroglial cells, or glia, which outnumber neurones by about an order of magnitude. Unlike neurones, neuroglia do not have a direct role in information processing but they fulfil a number of other roles that are essential for the normal functioning of the further specialised to detect changes in the external or internal nervous system. One type of glial cell (the oligodendrocyte) is environment. One of the processes attached to the cell body is responsible for the production of myelin, a structure high in called the axon (nerve fibre) and this carries information away lipoprotein that ensheathes many axons and greatly increases the from the cell body. Axons are highly variable in length and may speed of conduction of action potentials. divide into several branches, or collaterals, through which information can be distributed to a number of different Central and peripheral nervous systems destinations simultaneously. At the end of the axon, synaptic At a simple anatomical level, the nervous system (Fig. 1.5) is specialisations called nerve terminals (presynaptic endings; divided into the central nervous system (CNS) and the terminal boutons) occur, from which information is transferred, peripheral nervous system (PNS). The central nervous system usually to the dendrites of other neurones. In efferent or motor consists of the brain and spinal cord, lying within the protection neurones, which control non-neural structures such as muscle of the cranium and vertebral column, respectively. It is the most cells, the axon al endings may be further specialised ( e.g. the complex part of the nervous system, containing the majority of neuromuscular junction). nerve cell bodies and synaptic connections. The peripheral Information is coded and distributed within neurones by nervous system constitutes the link between the CNS and changes in electrical charge. The cell membrane of neurones is structures in the periphery of the body, from which it receives polarised, which means that an electrical potential difference (the sensory information and to which it sends controlling impulses. membrane potential) exists across it. In the resting state, this The peripheral nervous system consists of nerves joined to the potential difference (the resting potential) is of the order of brain and spinal cord (cranial and spinal nerves) and their 60-70 millivolts (mV), the inside of the cell being negative with ramifications within the body. Spinal nerves serving the upper or respect to the outside. When a neurone is stimulated or excited lower limbs coalesce to form the brachial or lumbar plexus, above a certain threshold level, there is a brief reversal of the respectively, within which fibres are redistributed into named polarity of its membrane potential, termed the action potential. peripheral nerves. The PNS also includes many peripherally Action potentials are propagated down the axon and invade the located nerve cell bodies, some of which are aggregated within nerve terminals. At most synapses, transmission of information structures called ganglia. between neurones occurs by chemical rather than electrical means. Invasion of nerve terminals by an action potential causes the Somatic and autonomic nervous systems release of specific chemicals (neurotransmitters) that are stored in At a functional level, neurones that are concerned with detecting synaptic vesicles in the presynaptic ending. The neurotransmitter changes in the external environment, or with the control of 4 NEUROANATOMY ~---Afferent nerve ending [B(all ff Afferent neurone A F.-A Cranial nerve Afferent neurone cell body Spinal cord J"t ~I in peripheral ganglion Direction of flow' of nerve impulses ' [pterneuroner Ny/FI!TI] Spinal nerve Grny rnatte,1-1 White matter-:_) 4 Lumbar h] plexus Efferent neurone Efferent nerve ending Fig. 1.6 The general arrangement of afferent, efferent and interneurones. Peripheral nerve egg[ information they cany reaches consciousness, they are also called sensory neurones. Efferent neurones cany impulses away from the CNS and if they innervate skeletal muscle to cause movement, they are also called motor neurones. The vast majority of neurones, however, are located entirely within the CNS and are referred to as interneurones. The terms 'afferent' and 'efferent' are also commonly used to denote the polarity of projections to and from structures within the CNS, even though the projections are entirely contained within the brain and spinal cord. The projections to and from the cerebral cortex, for example, are referred to as cortical afferents and efferents, respectively. Grey and white matter, nuclei and tracts The CNS is a highly heterogeneous structure in terms of the distribution of nerve cell bodies and their processes (Fig. 1.7). Fig. 1.5 Central and peripheral nervous systems. Some regions are relatively enriched in nerve cell bodies (e.g, the central portion of the spinal cord and the surface of the cerebral hemisphere) and are referred to as grey matter. Conversely, other regions contain mostly nerve processes (usually axons). These are movement, are collectively referred to as the somatic nervous often myelinated (ensheathed in myelin), which confers a paler system. Neurones that detect changes in, and control the activity coloration = hence the term white matter. Nerve cell bodies with similar anatomical connections and of, the viscera are collectively referred to as the autonomic nervous system. Somatic and autonomic components are present functions ( e.g. the motor neurones innervating a group of related in both the central and peripheral nervous systems. The muscles) tend to be located together in groups called nuclei. autonomic nervous system is divided into two anatomically and Similarly, nerve processes sharing common connections and functions tend to follow the same course, running in pathways or functionally distinct parts, namely the sympathetic and parasympathetic divisions, which generally have opposing tracts (Fig. 1.7 and see Fig. 1.23). (antagonistic) effects on the structures that they innervate. The Decussation of sensory and motor pathways autonomic nervous system innervates smooth muscle, cardiac It is a general principle of the organisation of the CNS that muscle and secretory glands. It is an important part of the pathways conveying sensory information to a conscious level (the homeostatic mechanisms that control the internal environment of cerebral hemisphere) cross over, or decussate, from one side of the body. the CNS to the other. The same is true of descending pathways Afferent neurones, efferent neurones and from the cerebral hemisphere that control movement. Therefore in interneurones general, each cerebral hemisphere perceives sensations from, and controls the movements of, the opposite ( contralateral) side of the Nerve cells that carry information from peripheral receptors to the CNS are referred to as afferent neurones (Fig. 1.6). If the body.  Chapter 1 Introduction and overview 5 I Subcortical nuclei ------ Ascending and descending tracts Cerebral hemisphere Grey matter (Cerebral cortex) Midbrain White matter Pons }[Q[[)S[Q[[) [\[ell[a Fig. 1.7 Coronal section through the brain illustrating the distribution of grey and white matter. The section has been stained by Mulligan's technique, which colours grey matter blue, leaving white matter relatively unstained. Components and organisation of the nervous system Development of the central The structural and functional and spinal nerves and their nervous system unit of the nervous system is the ramifications. nerve cell, or neurone. Neurones The autonomic nervous system By the beginning of the second week of human embryonic have a resting membrane development, three germ cell layers become established: ectoderm, (ANS) innervates visceral potential of about -70 mV structures and is important in mesoderm and endoderm. Subsequently, these each give rise to A neurone receives information homoeostasis of the internal particular tissues and organs in the adult. The ectoderm gives rise primarily through its dendrites environment. to the skin and the nervous system. The mesoderm forms skeletal, and passes this on by action Individual neurones may be muscular and connective tissues. The endoderm gives rise to the potentials, which are carried defined as either afferent or away from the cell body by the alimentary, respiratory and genitourinary tracts. efferent with respect to the axon. The process of formation of the embryonic nervous system is CNS, or as interneurones. Information is passed between referred to as neurulation. During the third week of embryonic Within the CNS, areas rich in neurones at synapses by development, the dorsal midline ectoderm undergoes thickening either nerve cell bodies or nerve release of neurotransmitters to form the neural plate (Figs 1.8, 1.9). The lateral margins of the fibres constitute grey or white from presynaptic terminals; matter, respectively. neural plate become elevated, forming neural folds on either side these act upon receptors in the postsynaptic membrane to Clusters of cell bodies with of a longitudinal, midline depression, called the neural groove. cause either depolarisation or similar functions are known as The neural folds then become apposed and fuse together, thus hyper polarisation of the nuclei. sealing the neural groove and creating the neural tube. Some cells post synaptic cell. from the apices of the neural folds become separated to form Tracts, or pathways, of nerve Neuroglial cells are more fibres link together distant groups lying dorsolateral to the neural tube. These are known as numerous than nerve cells and regions. the neural crests. The formation of the neural tube is complete by have roles other than Generally, ascending sensory about the middle of the fourth week of embryonic development. information processing. pathways and descending Enormous growth, distortion and cellular differentiation occur The nervous system is divided motor pathways in the CNS during the subsequent transformation of the neural tube into the into the central nervous system decussate along their course, (CNS), which consists of the so that each side of the brain is adult CNS. This is maximal in the rostral part, which develops brain and spinal cord, and the functionally associated with the into the brain, the caudal portion becoming the spinal cord. The peripheral nervous system contralateral half of the body. central cavity within the neural tube becomes the central canal of (PNS), which consists of cranial the spinal cord and the ventricles of the brain. The neural crests form the sensory ganglia of spinal and cranial nerves, and also the autonomic ganglia. 6 NEUROA Ectoderm Mesoderm '-------Endoderm ~---- Neural plate Neural fold li~~-- Neural groove l Neural crest Neural tube mw"if. L »ie ",""a»ibis\5"",",,rdii I ctron rog ' sot tran b O +ir illustrating the : Fig. 1.9 from the embryonic - --. Schematic representation ·i ectoderm.. o f the formation of the neural tube ogggg""z, through the (Courtesy o ors to bottom) in formation o biology and Anatomy, S hool of Medicine, University of Utah c a  Chapter 1 Introduction and overview 7 As development continues, a longitudinal groove, the sulcus basic developmental pattern can still easily be recogn.ised in the limitans, appears on the inner surface of the lateral walls of the adult spinal cord (Fig. 1.10B). embryonic spinal cord and caudal part of the brain (Fig. 1. lOA). Further differentiation distinguishes seven neuronal cell The dorsal and ventral cell groupings thus delineated are referred groupings within the alar and basal plates (Fig. 1.11). These are to as the alar plate and the basal plate, respectively. Nerve cells arranged in discontinuous longitudinal columns, based on their that develop within the alar plate have predominantly sensory anatomical connections and physiological roles: functions, while those in the basal plate are predominantly motor. Special somatic afferent: associated with the developing inner ear Further development also brings about the differentiation of and ultimately receiving auditory and vestibular input. grey and white matter. The grey matter is located centrally around General somatic afferent: receiving general sensory input from the central canal, with white matter forming an outer coat. This the periphery. Special visceral afferent: subserving the sense of taste. General visceral afferent: receiving afferent input from the viscera. Afferent neurone General visceral efferent: composed of preganglionic autonomic \ Alar plale efferents. Slug [inia[Sf[ Branchial efferent: containing motor neurones to muscles --1-'-----1---Basal plate derived from branchial (pharyngeal) arches. Somatic efferent: containing motor neurones to somatic muscles. Efferent neurone During embryonic development, the rostral portion of the neural tube undergoes massive differentiation and growth to form the brain (Fig. 1.12). By about the fifth week, three so-called primary brain vesicles can be identified: the prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain). The longitudinal axis of the developing CNS I Dorsal horn (neuraxis) does not remain straight but is bent by a midbrain or g \ Central canal cephalic flexure, occurring at the junction of midbrain and forebrain, and a cervical flexure between the brain and the spinal 7 Ventral horn I cord. Efferent neurone?3 ' By the seventh week, further differentiation distinguishes five (ventral root of l/hite matter secondary brain vesicles produced by division of the spinal nerve) prosencephalon into the telencephalon and diencephalon and ® division of the rhombencephalon into the metencephalon and myelencephalon. The junction between the latter is marked Fig. 1.10 Schematic representation of transverse sections through (A) the developing neural tube and (B) the adult spinal cord. Neuronal by an additional bend in the neuraxis, called the pontine connections with peripheral structures are illustrated only on one side. flexure. Special somatic afferent------~~ General somatic afferent-----~ Special visceral afferent--------/-___,/__ , General visceral afferent-------1---+-+- General visceral efferent-------1----++ [3[a\Ch\al[[010' f < 59[)3[[Cg[[erg[' (- Fig. 1.11 Schematic transverse section through the developing nervous system showing the arrangement of afferent and efferent cell groupings. The colour coding is recapitulated in Fig. 10.2, which illustrates the arrangement of cranial nerve nuclei in the adult brainstem, and in Table 10.1 which describes the components and functions of the cranial nerves..  r 8 NEUROANATOMY Mesencephalon rD Developmental anomalies Prosencephalon Disorders of development disrupt the normal growth and structural organisation of the spinal cord and brain. Because the nervous system is derived from embryonic ectoderm, these developmental anomalies }> Rhombencephalon also involve the coverings of the nervous system (skin and bone). In Cephalic flexure anencephaly, the brain and skull are minute and the infant does not usually survive. In spina bifida, the lower spinal cord and nerve roots are underdeveloped and may lie uncovered by skin or the bony spine 'SDI[\al CO[] on the infant's back (meningomyelocele). Such infants are left with withered, paralysed and anaesthetic lower limbs together with incontinence of the bowel and bladder. As the brain develops, its central cavity also undergoes considerable changes in size and shape, forming a system of Diencephalon----- ) Mesencephalon chambers or ventricles (Fig. 1.13 and see Fig. 1.23), which contain cerebrospinal fluid. Telencephalon Parallels have been drawn between the embryological development of the brain and the major changes that the brain Metencephalon has undergone during ascent of the phylogenetic, or evolutionary, scale from simple to more complex animals. Although this is certainly an oversimplification, the concept does have the Cephalic fiexure-----~ Myelencephalon educational merit of introducing some of the principal parts of Cervical flexure Spinal cord the brain, and their relationships to one another, in a graphic and e» memorable way (Fig. 1.13). The simplest of chordate animals (e.g. amphioxus), from which Fig. 1.12 The early development of the brain. (A) The primary brain vesicles at about 4 to 5 weeks and (B) the secondary brain vesicles at the vertebrates evolved, possess a dorsal tubular nerve cord that is about 7 to 8 weeks. reminiscent of the neural tube of the developing mammalian embryo. During phylogeny, the rostral end of the tubular nervous system has undergone enormous modification and change; consequently, the adult human brain bears little obvious similarity to its evolutionary ancestors. Regional specialisation has been an important theme in the evolution of the brain and this is especially obvious in relation to Table 1.1 Embryonic development of the brain. the senses and in movement control. Long ago in phylogeny, Primary brain vesicles Secondary Derivatives in brain vesicles mature brain centres devoted to these functions developed as expansions or Prosencephalon (forebrain) Telencephalon Cerebral hemisphere outgrowths from the dorsal aspect of the simple tubular brain Diencephalon Thalamus (Fig. 1.13). In form, they consisted of an outer cortex of nerve cell Mesencephalon (midbrain) Mesencephalon Midbrain bodies with an underlying core of nerve fibres. Bilaterally paired Rhombencephalon (hindbrain) Metencephalon Pons, cerebellum centres developed in relation to the senses of smell, vision and Myelencephalon Medulla oblongata hearing, and a symmetrical, midline centre developed in association with vestibular function and the maintenance of equilibrium. Each of these centres underwent subsequent evolutionary change, but this was most evident in the rostral, 'olfactory', part of the brain, which developed into the massive cerebral hemispheres (Figs 1.14, 1.15). During this process, known as prosencephalisation, the cerebral hemispheres Some of the names of the embryological subdivisions of the came to take on an executive role in many areas of brain function. brain are commonly used for descriptive purposes and it is, For example, the highest level for the perception and therefore, useful to know the parts of the mature brain into which interpretation of input from all sensory modalities eventually they subsequently develop (Table 1. 1 ). Of the three basic divisions became localised in the cortical surface of the cerebral of the brain, the prosencephalon or forebrain is by far the largest. hemispheres, as did the highest level for voluntary motor control, It is also referred to as the cerebrum. Within the cerebrum, the This is reflected by the fact that only a small proportion of the telencephalon undergoes the greatest further development and adult human cerebral hemisphere remains devoted to olfactory gives rise to the two cerebral hemispheres. These consist of an function. outer layer of grey matter (the cerebral cortex) and an inner mass The process of prosencephalisation meant that the other of white matter, within which various groups of nuclei lie buried integrative centres became progressively subservient to the cerebral (the largest being the corpus striatum). The diencephalon consists hemispheres. For example, those for vision and hearing underwent largely of the thalamus, which contains numerous cell groupings relatively little further development and fulfil largely automatic, and is intimately connected with the cerebral cortex. The reflex functions in the human brain. They may still be identified, mesencephalon, or midbrain, is relatively undifferentiated (it still however, as four small swellings on the dorsal surface of the retains a central tube-like cavity surrounded by grey matter). The midbrain: the corpora quadrigemina or superior and inferior metencephalon develops into the pons and overlying cerebellum, colliculi (Figs 1. 13, 1.14, 1. 15). The motor centre near the caudal while the myelencephalon forms the medulla oblongata end of the brain developed into the cerebellum (Figs 1. 13, 1.14, (medulla). The medulla, pons and midbrain are collectively 1.15), which retains a central role in the maintenance of referred to as the brainstem (Fig. 1. 13). equilibrium and the coordination of movement.  Chapter 1 Introduction and overview 9 __________ Cerebral hemisphere r+----~-1'----------- lnterventricular foramen ------Third ventricle o L-------- Globus pallidus -------Thalamus l:ateral ventricle Forebrain / ______ Superior colliculus = Inferior colliculus ] 7 Cerebral aqueduct ' -----Cerebellum Pees~ ------Fourth ventricle Brainstem Central canal Spinal cord Fig. 1.13 Schematic representation of the major subdivisions and landmarks of the brain.  ,, 10 NEUROANATOMY Cerebellum Pineal gland Cerebral hemisphere Inferior colliculus Superior colliculusf,f/, Corpus callosum ----f-:--:::l.F:'t--:IW..:.- Thalamus ; } Hypothalamus ---~"c-''"' Midbrain ---------~ ® Cerebellum Cerebral hemisphere ~---- Great longitudinal fissure ~k---- Cerebral hemisphere ~~::c--~--"IIH..--- Hypothalamus ff®h} Midbrain ~~~-t:fflt:W::-::---.f'---Medulla /iiihEEit Cerebellum © Cerebellum Fig. 1.14 Photographs of the brain. (A) Lateral aspect; (B) median sagittal section; (C) superior aspect; (D) inferior aspect.  Chapter 1 Introduction and overview 11 ~---- Thalamus Corpus callosum -------~ Pineal gland lnterventricular foramen ------ ' Superior and inferior colliculi [lypO[ala[US l > Q Cerebellum [pfundibulum=7 Fourth ventricle Midbrain ____, Cerebral aqueduct -4-----------Medulla (ereb(a][e[[SD/0[0 p4 [nfundibUlumafISIg [ L from hypothalamus ® Fig. 1.15 Principal subdivisions and some important landmarks in the mature brain. (A) Median sagittal section; (B) inferior aspect. Cranial nerves are indicated in yellow. Overview of the anatomy of the central surrounds the brain and spinal cord like a loose-fitting bag nervous system (Fig. 1.17). The spinal dura and much of the cranial dura are separate from the periosteum, which forms the inner lining of the Coverings and blood supply surrounding bones. At certain locations, however, such as on the The brain and spinal cord are supported and protected by the floor of the cranial cavity, the dura and periosteum are fused and bones of the skull and vertebral column, respectively. Within these the cranial dura is tightly adherent to the interior surface of the bony coverings, the CNS is entirely ensheathed by three concentric skull. In addition, two large sheets (or reflections) of dura project layers of membranes, called the meninges (Fig. 1.16). The into the cranial cavity, incompletely dividing it into compartments outermost membrane is the dura mater, a tough, fibrous coat that (Fig. 1.18). One of these, the falx cerebri lies in the sagittal plane  ? 12 NEUROANATOMY Skin Dura mater Bone Dura mater Arachnoid mater Trabeculae Pia mater Cerebral cortex Spinal nerve Blood vessel roots ensheathed in dura White matter Fig. 1.16 A section through the skull, illustrating the relationships between the meninges and the CNS. lb-±->Epidural SDaCe between the two cerebral hemispheres. Its free border lies just above the corpus callosum. The other dural sheet, the tentorium cerebelli, is oriented approximately horizontally, lying beneath the occipital lobes of the cerebral hemispheres and above the cerebellum. The tentorium cerebelli is continuous with the posterior part of the falx cerebri. The dura mater can be regarded as consisting of two layers. These are fused together except in certain locations, where they become separated to form spaces, the dural venous sinuses, which serve as channels for the venous drainage of the brain. Important dural sinuses occur: On the floor of the cranial cavity Along the lines of attachment of the falx cerebri and ten tori um cerebel Ii to the interior of the skull ( superior sagittal sinus, Fig. 1.17 Dorsal (posterior) aspect of the vertebral column after laminectomy to expose the vertebral canal and dura mater enclosing Fig. 1. 18; transverse sinus, see Figs 7.9, 7.10) the spinal cord. Along the line of attachment of the falx cerebri and ten tori um cerebelli to one another (straight sinus, see Figs 7.9, 7.10) Beneath the dura lies the arachnoid mater, the two being separated by a thin subdural space. The arachnoid is a Coverings and blood supply of the central translucent, collagenous membrane that, like the dura, loosely nervous system envelops the brain and spinal cord. The innermost of the The brain and spinal cord are Beneath the arachnoid mater meninges is the pia mater, a delicate membrane of microscopic invested by three meningeal lies the subarachnoid space in thickness that is firmly adherent to the surface of the brain and layers: the dura mater, which cerebrospinal fluid (CSF) spinal cord, closely following their surface contours. Between the arachnoid mater and pia mater. circulates. arachnoid and pia is the subarachnoid space through which Two sheets of cranial dura The brain is supplied with blood cerebrospinal fluid (CSF) circulates. mater, the falx cerebri and by the internal carotid and tentorium cerebelli, incompletely vertebral arteries. The brain is supplied with arterial blood by the internal carotid divide the cranial cavity into and vertebral arteries, which anastomose to form the circulus The spinal cord is supplied with compartments. arteriosus (circle of Willis) on the base of the brain. The spinal blood by vessels that arise from The cranial dura mater contains the vertebral arteries, reinforced cord is supplied by vessels arising from the vertebral arteries, dural venous sinuses, which act by radicular arteries derived reinforced by radicular arteries derived from segmental vessels. as channels for the venous from segmental vessels. The arteries and veins serving the CNS run for part of their course drainage of the brain. within the subarachnoid space (Fig. 1.16). The meninges are supplied by a number of vessels, the most significant intracranial one being the middle meningeal artery, which ramifies extensively between the skull and dura mater overlying the lateral aspect of the cerebral hemisphere.  Chapter 1 Introduction and overview 13 tr>Falx cereDrI Superior sagittal sinus " Corpus callosum tt! Tentorium cerebelli (containing straight sinus) " Cerebellum } Brain$teI. Fig. 1.18 Parasagittal section of the head showing the disposition of the falx cerebri and tentorium cerebelli. Anatomy of the spinal cord separation of cell bodies from nerve fibres confers a characteristic The spinal cord lies within the vertebral (spinal) canal of the '1-1' - or 'butterfly'- shape to the central core of grey matter that vertebral column and is continuous rostrally (superiorly) with the surrounds the central canal. Four projections of the central grey medulla oblongata of the brainstem (Fig. 1.19). The spinal cord matter extend dorsolaterally and ventrolaterally towards the lines receives information from, and controls, the trunk and limbs. This of attachment of the dorsal and ventral roots of the spinal nerves. is achieved through 31 pairs of spinal nerves that are attached to These projections are known as the dorsal (posterior) horns and the cord at intervals along its length and which contain afferent ventral (anterior) horns, respectively. The dorsal horn is the site and efferent nerve fibres connecting with structures in the of termination of numerous afferent neurones, conveying periphery. Near to the cord, the spinal nerves divide into dorsal impulses from sensory receptors throughout the body, and is the (posterior) and ventral (anterior) roots, which attach to the cord site of origin of ascending pathways carrying sensory impulses to along its dorsolateral and ventrolateral borders, respectively the brain. The ventral horn contains motor neurones that (Fig. 1.20). The dorsal roots carry afferent nerve fibres, the cell innervate skeletal muscle. In addition, at thoracic and upper bodies of which are located in dorsal root ganglia. The ventral lumbar levels of the cord only, another, smaller, collection of cell roots carry efferent nerve fibres, the parent cell bodies of which lie bodies comprises the lateral horn. This contains preganglionic within the spinal grey matter. Spinal nerves leave the vertebral neurones belonging to the sympathetic division of the autonomic canal through small apertures, called intervertebral foramina, nervous system (Chapter 4). which are located between adjacent vertebrae. Because of the The periphery of the spinal cord consists of white matter that difference in the rates of growth of the spinal cord and vertebral contains longitudinally running nerve fibres. These are organised column during development, the spinal cord in the adult does not into ascending tracts and descending tracts. Ascending tracts extend for the full length of the vertebral canal, but ends at carry information derived from the trunk and limbs to the brain. approximately the level of the intervertebral disc between L1 and Descending tracts are the means by which the brain controls the L2 vertebrae. The lumbar and sacral spinal nerves, therefore, activities of neurones in the spinal cord (Fig. 1.21). The principal descend in a leash-like arrangement, called the cauda equina ascending tracts are the dorsal columns (fasciculus gracilis and (Fig. 1.19), to reach their exit foramina. fasciculus cuneatus), which carry.fine touch and proprioception, The spinal cord is a relatively undifferentiated structure the spinothalamic tracts, which carry pain, temperature, coarse compared with the brain. Consequently, the basic principles of touch and pressure, and the spinocerebellar tracts, whim carry organisation, established early in embryonic development, can information from muscle and joint receptors to the cerebellum. still be readily identified even in the adult human spinal cord Among the descending tracts, one of the most important is the (Fig. 1.20). The spinal cord is approximately cylindrical in shape, lateral corticospinal tract, which controls skilled voluntary containing at its centre a vestigial central canal. The relative movements.  [)gISal COlUITTS r 4 LB± +oso Spinocerebellar, Lateral corticospinal tracts tract Spinothalamic khh>Dorsal TOO'S Of tracts spinal nerve Fig. 1.21 Transverse section through the spinal cord showing the locations of the principal ascending and descending nerve fibre tracts. Ascending tracts are only depicted on the left side and descending only on the right, although both occur bilaterally. Anatomy of the spinal cord The spinal cord lies within the Within the grey matter, the vertebral canal. It bears 31 dorsal horn contains sensory pairs of spinal nerves through neurones, the ventral horn which it receives fibres from, contains motor neurones and and sends fibres to, the the lateral horn contains periphery. preganglionic sympathetic neurones. Near the cord, spinal nerves @i4 SpIhal COTOp divide to form dorsal and Within the white matter run ventral roots; dorsal roots carry ascending and descending afferent fibres with cell bodies in nerve fibre tracts, which link the dorsal root ganglia, and ventral spinal cord with the brain. roots carry efferent fibres. The principal ascending tracts The spinal cord consists of a are the dorsal columns, the central core of grey matter, spinothalarnic tracts and the containing nerve cell bodies, spinocerebellar tracts. The and an outer layer of white corticospinal tract is an matter containing nerve fibres. important descending tract. Anatomy of the brain [pg+pl Cauda equina Major features and landmarks The brain is dominated by the cerebral hemispheres (Figs 1.14, 1.15, 1.22). These have a highly convoluted outer mantle of grey matter, the cerebral cortex, and an inner core of white matter, within which are located further masses of grey matter. Certain of Fig. 1.19 Dorsal (posterior) aspect of the spinal cord in situ. This is the the surface convolutions of the cerebral hemisphere have specific same specimen as shown in Fig. 1.17.The dura mater/arachnoid mater have sensory or motor functions, as described below. The two cerebral been incised longitudinally to expose the spinal cord and spinal nerve roots lying within the subarachnoid space. hemispheres are incompletely separated by a deep cleft, the great longitudinal fissure. The fissure is occupied by the falx cerebri and in its depths lies the corpus callosum, containing commissural nerve fibres that run between corresponding regions Dorsal root r Dorsal horn ganglion of the two hemispheres. The brainstem can be seen clearly when the brain is viewed Dorsal root from its inferior aspect, although the relationships of the of spinal nerve midbrain with other brain regions are best illustrated in sagittal section (Fig. 1.14B). The brainstem is the origin of 10 of the 12 pairs of cranial nerves (IHI-XII). Dorsal (posterior) to the Spinal nerve - brainstem is located the cerebellum. The tentorium cerebelli lies Ventral root of spinal nerve l» Ventral horn between the cerebellum and the posterior part of the cerebral hemispheres (occipital lobes). Ventricular system The highly simplified plan of the basic brain, described above Central Canal (Fig. 1.13), is a useful one on which to consider the general Fig. 1.20 Schematic diagram of a transverse section through the disposition of the ventricular system (Figs 1.15, 1.23). As the spinal cord, showing the attachment of spinal nerve roots and the central canal of the spinal cord is followed rostrally towards the arrangement of grey and white matter. brainstem, it moves progressively in a dorsal direction, eventually " opening out to form a shallow, rhomboid-shaped depression on the dorsal surface of the medulla and pons (the hind brain portion of the brainstem) beneath the cerebellum. The cavity thus formed is the fourth ventricle.  Chapter 1 Introduction and overview 15 Corpus callosum lnterventricular foramen---~ Thalamus Cerebral aqueduct Hypothalamus ! Midbrain Fourth ventricle Pons Cerebellum Medulla Fig. 1.22 Sagittal magnetic resonance image (MRI) of the head. The thalamus and hypothalamus form the upper and lower parts, respectively, of the lateral wall of the third ventricle. (Courtesy of Professor A Jackson, Wolfson Molecular Imaging Centre, University of Manchester, Manchester, UK.) lnterventricular foramen ------------- ~---- Body of lateral ventricle Anterior horn of lateral ventricle ---------~ Posterior horn of [hjr]ye['[[ClQhj lateral ventricle laInferior horn of teral ventri cle ' Cerebral aqueduct F Fourth ventricle ; Fig. 1.23 The cerebral ventricular system. At the rostral border of the pons, the walls of the fourth Brainstem ventricle converge, forming once again a narrow tube, the cerebral The large cerebral hemispheres obscure many other structures aqueduct. The cerebral aqueduct dives into the substance of the from view, but the brainstem can be seen clearly on both a brainstem, running the length of the midbrain beneath the median sagittal section and an inferior view of the brain inferior and superior colliculi. At the junction of midbrain and (Figs 1.14, 1.15). The brainstem consists of the medulla forebrain, the aqueduct opens into the third ventricle, a slit-like oblongata, pons and midbrain. chamber, narrow from side to side but extensive in dorsoventral The brainstem forms only a small proportion of the entire brain and rostrocaudal dimensions. The lateral walls of the third but it is crucially important. Through it pass all of the ascending ventricle are formed by the thalamus and hypothalamus of the and descending nerve fibre tracts linking the brain and spinal cord diencephalon. Near the rostral end of the third ventricle, a small (Fig. 1.24). These tracts carry sensory information from, and aperture, the interventricular foramen (foramen of Monro), control the movement of, the trunk and limbs. The brainstem also communicates with an extensive chamber, the lateral ventricle, contains the sites of origin and termination of most of the cranial within each cerebral hemisphere. The ventricular system contains nerves, through which the brain innervates the head. Moreover, cerebrospinal fluid (CSF), which is secreted by the choroid plexus within the brainstem lie centres that control the vital functions of (Chapter 6). breathing, the circulation of blood and the level of consciousness.  », g a 16 NEUROANATOMY. ·. · ; rr \/eSDUlaf TUClel Hypoglossal nucleus ~--- Inferior cerebellar peduncle Medial lemniscus g!LE'I Pyraff)[(] Fig. 1.24 Transverse section through the brainstem at the level of the medulla oblongata. The section has been stained by the Weigert-Pal method. Areas rich in nerve fibres stain darkly, while areas rich in cell bodies are relatively paler. The pyramid is a tract that contains descending motor fibres running from the cerebral cortex to the spinal cord. The medial lemniscus is a tract consisting of ascending axons carrying sensory information from the limbs to higher centres in the brain. The inferior cerebellar peduncle contains spinocerebellar fibres carrying information from joints and muscles to the cerebellum. The vestibular nuclei are the site of termination of the vestibular nerve, which carries information from the inner ear regarding the position and movement of the head. The hypoglossal nucleus is the site of origin of hypoglossal nerve fibres that innervate the muscles of the tongue. The medulla oblongata is continuous caudally with the spinal the surface. The cerebellum is concerned with the coordination of cord and extends rostrally as far as the pons. The ponto-medullary movement and it operates at an entirely unconscious level. junction can be seen clearly on inferior or sagittal views since the Rostral to the pons is located the relatively small midbrain. On ventral part of the pons forms a prominent bulge on the surface its dorsal surface can be seen the rounded eminences of the of the brainstem. In sagittal section (Figs 1.14B, 1.15A), the superior and inferior colliculi, beneath which runs the cerebral lumen of the fourth ventricle is apparent between the pons and aqueduct (Figs 1.13, 1.14, 1.15). medulla ventrally and the cerebellum dorsally, into the latter of which its tent-shaped roof extends. Diencephalon and cerebral hemispheres Cranial nerves Rostral to the brainstem lies the forebrain, which consists of the The brain directly receives sensory information from, and controls diencephalon and the cerebral hemispheres. The diencephalon and the activities of, peripheral structures, principally of the head and cerebral hemisphere on each side of the brain are to a large extent neck. Afferent and efferent nerve fibres run in 12 bilaterally paired physically separate from their counterparts on the other side, cranial nerves, which are identified by individual names and by although important cross-connections do exist, as described below. Roman numerals !-XII. Certain of the cranial nerves contain only The two sides of the diencephalon are separated by the lumen of sensory or only motor nerve fibres but the majority contain a the third ventricle, of which they constitute the lateral walls. mixture, as is the case with spinal nerves,. The first two cranial The diencephalon consists of four main divisions: in a nerves (I olfactory, II optic) attach directly to the forebrain, whilst dorsoventral direction, these are the epithalamus, thalamus, the others attach to the brainstem. Within the brainstem lie a subthalamus and hypothalamus. The epithalamus is small and number of nerve cell body groupings called the cranial nerve its most notable component is the pineal gland, which lies in the nuclei. These are the sites of termination of sensory fibres, and the midline, immediately rostral to the superior colliculi of the origin of the motor fibres, that run in the cranial nerves ( e.g. midbrain (Figs 1.14B, 1.15A), The thalamus is by far the largest Figs 1.24, 10.2)., part of the diencephalon and it forms much of the lateral wall of the third ventricle. The thalamus plays an important part in Cerebellum sensory, motor and cognitive functions and it has extensive The cerebellum is attached to the brainstem by a large mass of reciprocal connections with the cerebral cortex. The subthalamus nerve fibres that lie lateral to the fourth ventricle on either side is a small region lying deep to the ventricular wall. It contains the (see Fig. 9.1). The mass is split nominally into three parts: the subthalamic nucleus, which is closely related functionally to the inferior, middle and superior cerebellar peduncles. These carry basal ganglia (Chapter 14). The hypothalamus forms the lower nerve fibres between the medulla, pons and midbrain, respectively, part of the walls, and the floor, of the third ventricle. It is a and the cerebellum. complex and highly important region because of its involvement The cerebellum consists of an outer layer of grey matter, the in the autonomic nervous system (Chapter 4), the limbic system cerebellar cortex, surrounding a central core of white matter and the neuroendocrine system (Chapter 16). From the ventral (Fig. 1.14B). The cortical surface is highly convoluted to form a aspect of the hypothalamus in the midline arises the regular pattern of narrow, parallel folds, or folia. The cerebellar infundibulum or pituitary stalk (Fig. 1.15A), to which is attached white matter consists of nerve fibres running to and from the the pituitary gland. cerebellar cortex. The white matter has a characteristic branching, The cerebral hemisphere is by far the largest part of the brain. tree-like arrangement in section, as its ramifications reach towards Like the cerebellum, it consists of an outer layer, or cortex, of grey  Chapter 1 Introduction and overview 17 --"---------Cerebral cortex '/if\/f[[@ [[)Q[[Q[ Great longitudinal JC fissure Lateral ventricle \/) 1 Corpus callosum Caudate nucleus [LL..,..,,,-----Lateral fissure [pternal Capsule 77] ( /Hypothalamus Globus pallidus---~ Temporal lobe Fig. 1.25 Coronal section through the cerebral hemisphere.