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Meningeal Coverings of the Brain and Spinal Cord

The meninges form a major part of the mechanical suspension system of the CNS, necessary to keep it from self-destructing as we move through the world. In addition, one layer of the meninges participates in the system of barriers that effectively isolates the extracellular spaces in the nervous system from the extracellular spaces in the rest of the body. There Are Three Meningeal Layers: The Dura…

Development of the Nervous System

Understanding a little bit about the embryology of the brain helps clarify the way it's put together in adults. The central nervous system (CNS) starts out as a simple ectodermal tube that develops some folds and bulges. The cavity of the tube persists as the ventricles, and the folds and bulges determine the shape and layout of many parts of the CNS. The Neural Tube and…

Introduction to the Nervous System

The brain seems bewilderingly complex the first few times you look at it. One way to ease the bewilderment is to have an overview of some vocabulary and organizing principles, which the first three chapters of this book attempt to provide. Chapter 1 is a quick introduction to the parts of the nervous system and the cells that make it up, Chapter 2 is an overview…

Hypothalamus, limbic system and olfactory system

In order to survive, there must be continual biochemical and physiological adjustments to preserve the internal environment of the body in a balanced and stable state (homeostasis). Interoceptor signals from the internal organs and body fluids initiate homeostatic responses to achieve this end and the hypothalamus is the structure responsible for orchestrating the task. Exteroceptive information concerning the outside world strongly influences behaviour. This is relatively…

Basal ganglia

Within the cerebral hemisphere lie a number of nuclear masses. Apart from the thalamus ( Chapter 12 ), the most prominent of these are the caudate nucleus , putamen and globus pallidus, which lie in close proximity to the internal capsule and are collectively referred to as the basal ganglia, basal nuclei or corpus striatum ( Figs 14.1 , 14.2 ; see also Figs 13.3 –…

Cerebral hemisphere and cerebral cortex

The cerebral hemisphere is derived from the embryological telencephalon ( Chapter 1 ). It is the largest part of the forebrain and it reaches the greatest degree of development in the human brain. Superficially, the cerebral hemisphere consists of a layer of grey matter, the cerebral cortex, which is highly convoluted to form a complex pattern of ridges ( gyri ; singular, gyrus ) and furrows…

Thalamus

Rostral to the midbrain lies the forebrain (prosencephalon, cerebrum; see Fig. 1.13 ). The forebrain consists of the bilaterally paired diencephalon and cerebral hemisphere on each side and is by far the largest derivative of the three basic embryological divisions of the brain. The diencephalon is continuous with the rostral part of the midbrain and lies between the brainstem and the cerebral hemisphere. From dorsal to…

Cerebellum

The cerebellum is the largest part of the hindbrain. It originates from the dorsal aspect of the brainstem and overlies the fourth ventricle. The cerebellum is connected to the brainstem by three stout pairs of fibre bundles, called the inferior , middle and superior cerebellar peduncles ( Figs 11.1, 11.4 ; see also Fig. 9.1, Fig. 9.2, Fig. 9.3 ); these join the cerebellum to the…

Cranial nerves and cranial nerve nuclei

There are 12, bilaterally paired, cranial nerves. These carry afferent and efferent nerve fibres between the brain and peripheral structures, principally of the head and neck. The cranial nerves are individually named and numbered (Roman numerals I–XII) according to the rostrocaudal sequence in which they attach to the brain ( Fig. 10.1 and Table 10.1 ): I olfactory II optic III oculomotor IV trochlear V trigeminal VI abducens VII facial VIII vestibulocochlear IX glossopharyngeal X vagus…

Brainstem

The brainstem consists of the medulla oblongata, pons and midbrain. The archaic term ‘bulb’ is applied to the brainstem in compound anatomical names given to nerve fibres originating from, or terminating in, the brainstem (e.g. ‘corticobulbar’ refers to axons that arise in the cerebral cortex and terminate in the brainstem). It is also used clinically to denote the medulla in such terms as ‘bulbar palsy’ and…

Spinal cord

The spinal cord and its associated spinal nerves are of immense functional importance. These structures act to: Receive afferent fibres from sensory receptors of the trunk and limbs Control movements of the trunk and limbs Provide autonomic innervation for most of the viscera The internal organisation of the cord permits many functions to operate in an automatic or reflex fashion. In addition, extensive connections with the…

Coverings of the central nervous system

The central nervous system (CNS) is supported and protected by bone and membranous coverings. The brain is located within the cranial cavity of the skull and the spinal cord lies in the vertebral, or spinal, canal within the vertebral column, or spine. Within their bony coverings, the brain and spinal cord are invested by three concentric membranous envelopes. The outermost membrane is the dura mater, the…

Peripheral nervous system

The peripheral nervous system consists of sensory and motor nerve endings, peripheral nerve trunks, plexuses and ganglia, which link the CNS with other parts of the body. Most of the neurones in the peripheral nervous system are, therefore, either afferent or efferent with respect to the CNS. Nerve endings include sensory receptors, that detect changes in the internal and external environments, and efferent endings, which control…

Cells of the nervous system

The functional unit of the nervous system is the nerve cell or neurone. These cells are highly specialised for the encoding, conduction and transmission of information. Neuroglial cells, or glia, are present in the nervous system in even larger numbers than neurones. Glia do not take part directly in information processing but are, nonetheless, crucial for normal neural function. Other cells are also present in the…

Introduction and overview

The nervous system of all animals functions to detect changes in the internal and external environments and to bring about responses in muscles, organs and glands that are appropriate for the preservation of the individual and the propagation of the species. In relatively primitive species such functions are focused primarily on: Maintenance of the internal environment (homoeostasis) Perception of, and response to, external stimuli/threats Finding food…