This chapter reviews the three types of cellular repair in the adult nervous system, in addition to the functional reorganization of surviving neurons and circuits that typically follows brain damage. The first and most effective is the regrowth of severed peripheral axons either from peripheral sensory neurons or central motor neurons, usually via the peripheral nerve sheaths once occupied by their forerunners. A second, and far more limited, type of repair is local sprouting or longer extension of axons and dendrites at sites of traumatic damage or degenerative pathology in the brain or spinal cord. A third type of repair is generation of new neurons in the adult brain. In most mammals, the olfactory bulb and the hippocampus are the only sites of adult neurogenesis in the central nervous system (CNS).
Chapter
Repair and Regeneration in the Nervous System
Edited by George J. Augustine, Jennifer Groh, Scott Huettel, Anthony-Samuel LaMantia, Leonard E. White, and Dale Purves,
Chapter
Nerve cells and their connections
This chapter examines the nervous system. The nervous system is adapted to provide rapid and discrete signalling over long distances. It is divided into the central nervous system (CNS) comprising the brain and spinal cord, and the peripheral nervous system comprising the peripheral nerves, the enteric nervous system, and autonomic nervous system. The chapter describes the two main types of cells that make up the nervous system: the nerve cells or neurons and the satellite cells. The chapter clarifies that the satellite cells in the brain and spinal cord are called glial cells or neuroglia, while elsewhere they have different names, such as Schwann cells, Müller cells, or pituicytes. The neurons are the fast-signalling elements of the nervous system.
Chapter
Introduction to the nervous system
This chapter focuses on the nervous system. This includes motor control and the basis of sensation. It outlines the organization of the nervous system and the nature of its constituent cells. The nervous system may be divided into five main parts: the brain, the spinal cord, peripheral nerves, the autonomic nervous system, and the enteric nervous system. The chapter discusses how the brain and spinal cord constitute the central nervous system (CNS), while the peripheral nerves, autonomic nervous system, and enteric nervous system make up the peripheral nervous system. The autonomic nervous system is the part of the nervous system that is concerned with the innervation of blood vessels and the internal organs, which includes the autonomic ganglia that run parallel to the spinal column and their associated nerves.
Chapter
General principles of sensory physiology
This chapter explores how people can smell the air, taste food, feel the earth under their feet, hear, and see what is around them. These all require some means of converting the physical and chemical properties of the environment into nerve impulses. Once a change in the environment is identified, the central nervous system (CNS) can determine the appropriate response and initiate the required course of action. The chapter reviews the process by which specific properties of the environment become encoded as nerve impulses called sensory transduction, which is carried out by specialized structures called sensory receptors. The chapter discusses the general principles that are involved in forming sensations. These sensations are a normal part of life. Different sensory receptors are specialized to respond to particular environmental factors.
Chapter
Cholinergics, anticholinergics, and anticholinesterases
This chapter describes drugs that have an effect on the cholinergic nervous system, citing several clinically important drugs that act on the peripheral and the central nervous system (CNS). It examines the involvement of CNS with nerves through the use of the neurotransmitter acetylcholine as a chemical messenger. It also covers drugs that influence the activity of motor nerves, which take messages from the CNS to various parts of the body, such as skeletal muscle, smooth muscle, cardiac muscle, and glands. The chapter details how motor nerves innervate skeletal muscle, nerves that synapse with other nerves in the peripheral nervous system, and the parasympathetic nerves innervating cardiac and smooth muscle. It reviews two types of cholinergic receptor: muscarinic receptors that are present in smooth and cardiac muscle and nicotinic receptors that are present in skeletal muscle and in synapses between neurons.
Chapter
Nervous System Organisation and Biological Clocks
This chapter examines the correlation between the organisation of the nervous system and biological clocks. It cites how the organisation of behavioural adaptation results from the function of the nervous system. The organisation of neurons into functional nervous systems allows for the complexity of neural control of animal physiology and behaviour. The chapter cites the central nervous system (CNS) and peripheral nervous system (PNS) as the major division in the nervous system in most animals. It explains how biological clocks endow animals with an intrinsic temporal organisation, which is a timed pattern of change in physiology or behaviour independent from a change in environment.
Chapter
Touch and Proprioception
Edited by George J. Augustine, Jennifer Groh, Scott Huettel, Anthony-Samuel LaMantia, Leonard E. White, and Dale Purves,
This chapter highlights the somatosensory system. The somatosensory system is arguably the most diverse of the sensory systems, mediating a range of sensations—touch, pressure, vibration, limb position, heat, cold, itch, and pain—that are transduced by receptors within the skin, muscles, or joints and conveyed to a variety of central nervous system (CNS) targets. Not surprisingly, this complex neurobiological machinery can be divided into functionally distinct subsystems with different sets of peripheral neurons that possess complex end organs and transmit somatosensory information through multiple central pathways. One subsystem transmits information from cutaneous mechanoreceptors and mediates the sensations of fine touch, vibration, and pressure. Another originates in specialized receptors that are associated with muscles, tendons, and joints and is responsible for proprioception—our ability to sense the position of our own limbs and other body parts in space.
Chapter
Early Brain Development
Edited by George J. Augustine, Jennifer Groh, Scott Huettel, Anthony-Samuel LaMantia, Leonard E. White, and Dale Purves,
This chapter explores early brain development. The elaborate architecture of the adult brain is the product of cell-to-cell signals, genetic instructions, and their consequences for stem cells that are set aside in the embryo during the earliest steps of development to generate the entire nervous system. These events include the establishment of the primordial central and peripheral nervous systems, the initial formation of the major brain regions, the generation of multiple classes of neurons and glial cells from undifferentiated neural stem or progenitor cells, and the migration of neurons or their immediate precursors from sites of generation to their final positions. These processes set the stage for the subsequent local differentiation of dendrites, axons, and synapses, as well as the growth of long-distance axon pathways and synaptic connections. When any of these processes goes awry, the consequences can be disastrous.
Chapter
Development of the nervous system
This chapter discusses the development of the nervous system. It recognizes the complexity of the nervous system in comparison to all the organ systems in the animal embryo. Moreover, the chapter mentions the divide between the central nervous system (CNS) and peripheral nervous system (PNS). It explores the different types and connections of neurons. In addition, the chapter explains how the nervous system is superficially similar to other developmental systems, except that it involves the acquisition of individual cell identities. It looks into how neural activity plays a major role in refining connections, such as those between the eye and the brain.
Chapter
Nerves: the cells of the central and peripheral nervous systems
Rosalind King and Richard Mathias
This chapter focuses on the cells that make up the structures of the nervous system, and looks at how they act together to facilitate all the functions of human life. The nervous system is often thought of as having two main components. The central nervous system (CNS) comprises the brain and spinal cord. From the CNS, nerve fibres project to the receptors and effectors in every other organ and tissue throughout the body, forming the peripheral nervous system (PNS). The chapter then describes the cells that make up the nervous system and their functions, looking at neurons and glial cells. It also explains the mechanisms of neuronal communication and outlines the arrangement and integration of the central and peripheral nervous systems.
Chapter
Vision
Edited by George J. Augustine, Jennifer Groh, Scott Huettel, Anthony-Samuel LaMantia, Leonard E. White, and Dale Purves,
This chapter describes the human visual system and its capacity to detect visible light. Not only must it be capable of collecting and conveying information about object location, size, color, texture, and motion, but it operates over a wide range of luminance values and stimulus intensities. The chapter assesses how the eye, the sensory organ of the visual system, collects and focuses visible light onto a light-sensitive layer of central nervous system (CNS) tissue; how photoreceptive cells transduce light energy into electrical signals that can be processed and transmitted by neurons; and how specialized circuits among neurons in the retina extract information about features in the visual scene and transmit it to the brain. It also considers how visual centers in the brain integrate feature-specific information to facilitate object recognition and visually guided behaviors. In addition, the chapter looks at the importance of coordinated eye movements.
Chapter
Embryo origami
This chapter explores the fascination of embryo origami. It provides an overview of the process of gastrulation, organogenesis, neurulation, and differentiation. Embryo origami occurs as the embryo develops, and a single cell transforms into sheets of cells to form complex three-dimensional organisms complete with tissues, organs, and organ systems. The chapter considers the intricacy of cell movements relative to one another that are used both during gastrulation and during the formation of the central nervous system. It explains that the differentiation of cells is often induced by complex patterns of epigenetic modification that radically alter gene expression patterns within the differentiating cells.
Chapter
Neurons, nerves and nervous systems
This chapter evaluates the nervous systems in animals. All animals except Placozoa and Porifera (sponges) have a well-defined nervous system, which is the main means of communication between the animal and the outside world. Animals with bilateral symmetry have a central and a peripheral nervous system. The central nervous system (CNS) in invertebrates is organized in ganglia close to sensory structures, while the CNS in vertebrates consists of the brain and the spinal cord. The chapter then looks at the ionic basis of electrical activity in neurons, before considering how neurons communicate with each other. Signal transmission between neurons takes place at synapses, which are of two types: electrical synapses and chemical synapses.
Chapter
Integration of the respiratory and circulatory systems
This chapter studies the integration of the respiratory and circulatory systems in animals. The activity of the respiratory pumps is produced within the central nervous system by a network of oscillating neurons: a central rhythm (pattern) generator. Meanwhile, the rhythmic activity of the circulatory pumps (hearts) is produced in most groups of animals by myogenic pacemakers. The control of the pumps and the diameters of peripheral blood vessels in many circulatory systems rely on sensory information from chemoreceptors and mechanoreceptors. The chapter then looks at the generation of respiratory rhythm and control of the respiratory system, before considering the generation of the cardiac rhythm and control of the cardiovascular system. It also examines the location of terminations of the respiratory and cardiovascular sense organs in the central nervous system.
