The nervous system is collections of neurons, neuroglia, and nerve fibers specialized to convey signal with great speed and with great accuracy. The nervous system along with the endocrine system forms the major control system of the body. It receives input regarding changes in the internal environment and external environment through the ascending pathways from different parts of the body. And in response the command signals are sent to the effector organs of the body through descending pathways. Between these input and output channels there intervenes the working Brain, an information processing, data storing, decision making machine, the excutent organ of behavior. As in any other organ system of the body the aim of the nervous system also is to maintain the homeostasis of the internal environment. Sub divisions: (1) Central nervous system: Brain and spinal cord. (2) The peripheral nervous system-cranial nerves and spinal nerves. (3) Autonomic nerves system-sympathetic system, parasympathetic system. (4) The Enteric nervous system. On the functional basis the nervous system is classified into: (i) Motor system and (ii) Sensory system. All these divisions are there only for our study and understanding convenience. Actually their functions are interrelated, interdependent and some times overlapping. All these divisions work in a coordinated way to maintain the homeostasis. The structure of neurons, neuroglia and nerve fibres of different types and their properties described. Classifications of nerve fibers, and their diameter size, conduction rate, and their functions are placed in a tabular statement for ready reference and easy understanding. Properties of nerve fibers are described Resting potential, Action potential, and compound action potential are discussed. Nerve conduction, nerve degeneration, neuronal metabolism and electrical reaction of degeneration are described. In this section, chapter two deals with somatic sensation and its logical to begin the study of the nervous systems with sensory receptors for it is here that the stimulus which initiates and controls much activity impinging on the nervous system. All knowledge comes to us through sense organs. Activation of an organism depends on the receipt of stimulation. The receptors are classified into exteroceptors and interoceptors. The structure of the receptors to various and how they respond to various sensations are described. Superficial cutaneous sensations are light touch, light superficial pressure, temperature and pain and their cutaneous receptors namely Meissner’s corpuscles, Merkel’s disc, and basket like nerve endings around the hair follicle and their activity is discussed. Similarly structure of the deep receptors such as muscle spindle, tendon organs of Golgi are described. The muscle spindle structure, its innervation and its important role in stretch reflex is discussed in detail. The properties of receptors such as specificity, adaptation and law of projection are emphasized adequately. In this section, chapter three deals synapse, synaptic transmission and neurotransmitters and their structure, types, mechanisms and components are described. General characteristics of neurotransmitters are described. The well-established neurotransmitter and neurohumors are acetylcholine, norepinephrine, epinephrine, dopamine, serotonin, histamine, substance-P, glycine and gamma amino butyric acid (GABA). Lastly norepinephrine, epinephrine, dopamine, functions or described. Dopomine deficiency giving rise to Parkinson’s disease and; its features are mentioned. GABA and glycine are described as inhibitory transmitters. Finally opioid peptides, enkephalins, endorphins, lymphokines are explained as powerful analgesics and they produce these effects by binding to the opiate receptors. The nervous system functions are carried out principally by means of vast number of reflexes. The reflex action-components are described with aid of diagrams. The reflexes are classified into: (1) Clinical reflexes-superficial, deep and visceral reflexes. (2) Anatomically into: (i) Segmental, (ii) Inter-segmental, and (iii) Supra-segmental reflexes. (3) Physiologically into: (i) Extensor (ii) Flexor reflexes. (4) Conditioned and unconditioned reflexes. (5) Based on the effect of the effector organs—motor reflexes, glandular reflexes or secretary reflexes. The clinical reflexes are discussed in a large tabular statement with all details. Properties of reflex action are described in a very elaborate manner. Stretch reflex and muscle tone are explained. Withdrawal reflex and flexor reflexes described. Lengthening reaction explained. Chapter five deals with the help of color diagrams of the cross section of the spinal cord the grey matter and white matter of the spinal cord explained. In addition this diagram explains the cross section spinal cord to show the location of the ascending and descending tracts. The different ascending systems of tracts are named. Their origin, course, functions and their destination are discussed in a sequential order. Similarly the origin of descending pathways-corticospinal tract, or pyramidal tract and extra pyramidal tracts—there origin, course, destination and functions are described. The meaning of upper motor neuron and lower motor neuron are defined and features are explained with the help of a tabular statement. The clinical conditions associated with spinal cord-complete section are cord giving rise to paraplegia, Hemisection of cord, Tabes dorsalis and sphingomyelin are discussed. Chapter six dealt with receptor organs for various sensations. For touch or tactile sensation: Meissner’s corpuscles, Merkel’s disc and basket like nerve endings, Pacinian corpuscles and Ruffini’s end organ. Pain has no organized receptor organ. It is received by bare nerve endings. They belong to A-delta and C type of fibers. Pressure receptors are Pacinian corpuscle and Ruffini’s end organ. Vibratory sense is received by more them one receptors-touch receptor and Pecinian corpuscle. Joint sense namely vibration sense, sense of movement and sense of position are described. All afferent impulses both sensory and non-sensory originating from the periphery enter the spinal cord through dorsal nerve root and ascend through afferent or ascending tracts to the higher sensory centers situated in the cerebral cortical areas 3-1-2. Neurophysiology of pain is discussed in detail with adequate diagrams. Visceral pain and referred pain are discussed imparting their clinical importance. In this section chapter seven deals with the methods of localization of functions of cerebral cortex are narrated. Each lobe and the important functional areas in these lobs are detailed. The Frontal lobe: areas –4, 4 s, 6, 8, and 44 are described and their motor functions. Prefrontal lobe: areas -9, 12, 13, 14, 24 s, 32, and 47. There function in maintenance and development of normal personality, behavior and intellect are detailed. Parietal Lobe areas -3, -1, -2, 5, and 7 these are mainly concerned with sensory perception. Occipital lobe: area 17, 18, 19. These are concerned with vision. Temporal lobe: area 41, 42, 20, 21, 22. These are mainly involved in hearing. In this section, chapter 8 described names of a few pioneer workers who contributed to the knowledge of Limbic system and their components are given. The important limbic circuits-Amygdala connections and Hippocampus circuits are given in a diagram and their functions are discussed in details. In this chapter nine, is concerned with somatic motor functions. These are affected ultimately by skeletal or voluntary muscle. The upper motor neurons of both pyramidal and extrapyramidal systems arising from all levels central nervous systems: cortex, basal ganglia, midbrain, pons, medulla and medulla end in the spinal cord anterior horn cells which form the common final pathway for motor activity. Components of the extra pyramidal system and its connection are given in a diagram. Clinical conditions related to motor activity are discussed. In this chapter ten cerebellum, after describing the functional classification of cerebellum, its histology is described. The connections of neocerebellum, paleocerebellum and archicerebellum connection are described with the help of diagrams. The archicerebellum by its connections with vestibular nucleus and vestibular apparatus constitute an important mechanism in the maintenance of equilibrium. Paleocerebellum by its dorsal and ventral spinocerebellar tracts connected with spinal cord there by it plays an important role in the regulation of muscle tone. Neo cerebellum by its connections with neo cerebral cortex plays an important role in the regulation of coordination of voluntary movements. The important features of cerebellar lesion are described. In this section, Chapter eleven, muscle tone forms the basis for posture and posture provides a suitable background for the performance of the movements. Stretch reflex is myotatic reflex and its importance in muscle tone is explained. Muscle spindle and its innervation are dealt in detail. The various Postural reflexes are given in detail in a tabular statement for ready reference. Structure of the vestibular apparatus is described with an aid by the diagram. Vestibular nucleus its connections with both afferents and afferents are discussed. The role in the maintenance of equilibrium is explained. Clinical aspects: Motion sickness, Nystagmus, vertigo and Mennier’s disease are discussed. In this section chapter twelve dealt with thalamus and hypothalamus. The difficult subject of thalamic nuclear classification is made very simple by a supporting diagram with description of their afferent and efferent connections. Sensory function and its involvement in arousal and alerting reactions, its role in motor functions are explained. Clinical features of thalamic lesions are listed out. Hypothalamic nuclear divisions their afferent and efferent connection are described with supporting diagram. Hypothalamic functions: control of autonomic nervous system, regulation of body temperature, regulation of food intake regulation of endocrine functions, its role in sleep and the regulation of the circadian rhythm are discussed in detail. Clinical syndromes related to Hypothalamus are mentioned. In this section, chapter 13: Brain stem reticular formation (BSRF) components are discussed by the diagrams. Functional importance of reticular formation in consciousness and sleep-waking cycle, in conditioning and learning, its role in selective attention and sensory inattention, in the control of muscle tone and posture, in the control of visceral functions and in the control of neuroendocrine functions are enumerated adequately. Sleep-theories of sleep are explained. Different stages of sleep and their genesis is described. The genesis of electrical activity of brain, the methods recording EEG and the different normal EEG patterns are discussed. EEG patterns during different phases of sleep are given in diagram. The different uses of EEG in localizing tumour, hematoma, in epilepsy and to locate brain death are discussed. Chapter fourteen, autonomic nervous system is discussed under the following headings: (i) Organization, and its divisions, (ii) Parasympathetic and sympathetic biberes distributions to different organs, and (iii) Transmitters involved in there functions. The receptors responding to the neurotransmitters and their effects are discussed adequately. Diseases associated with ANS-Horner’s syndrome, Reynaud’s disease, Hirsch Prung’s disease are described. In this chapter fifteen: Speech, learning and memory are considered as higher functions of human beings. Cortical areas involved and organization of speech are given in the form of a diagram. The cortical areas involved in speech mechanism are motor area for speech (Brocas area) Wernicke’s are discussed in detail. The fact that the left cerebral hemisphere is the dominant hemisphere is very much emphasis. The speech disorder—aphasia is discussed. The conditioned reflexes and unconditioned reflexes are defined and differentiated. Conditioned reflexes form the vital part in the learning process is listed out. The relationship between conditioned reflexes and learning mentioned and their processes of learning and memory formation are discussed. Learning essentially consists of formation of new neuronal circuits and electrical activity in them besides structural changes. Memory and learning are like two sides of the coin. How memory is formed is explained. The processes involved in memory formation, registration, retention or storage and recall are well explained. The types of memory-short term memory, lung-term memory, are discussed at length. Role of Hippocampus in learning and memory and temporal cortical areas 20, 21, and 22, as storage sites are described. Clinical aspects – different types of Amnesia and Alzeimer’s disease are described. In this chapter 16: Cerebrospinal fluid—its circulation, composition and formation are discussed. Lumbar puncture procedure and its uses are described. Blood-brain-barrier mechanism and its usefulness are explained.