The nervous system is a highly specialized network whose principal components are nerves called neurons. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information Neurons are interconnected to each other in complex arrangements and have the property of conducting, using electrochemical signals, and a great variety of stimuli both within the nervous tissue as well as from and towards most of the other tissues. Thus, neurons coordinate multiple functions in organisms. Nervous systems are found in many multicellular animals but differ greatly in complexity between species. [1]
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Nervous system in humans
The human nervous system can be grouped into both with gross anatomy, (which describes the parts that are large enough to be seen with the naked eye,) and microanatomy, (which describes the system at a cellular level. Gross anatomy is the study of Anatomy at the macroscopic level. The naked eye is a Figure of speech referring to human Visual perception that is unaided by enhancing equipment such as a Telescope or Histology (from the Greek = 'tissue' is the study of the microscopic anatomy of cells and tissues of Plants and ) At gross anatomy, the nervous system can be grouped in distinct organs, these being actually stations which the neural pathways cross through. A neural pathway is a Neural tract connecting one part of the Nervous system with another usually consisting of bundles of elongated Myelin -insulated Thus, with a didactical purpose, these organs, according to their ubication, can be divided in two parts: the central nervous system (CNS) and the peripheral nervous system (PNS). In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. The peripheral nervous system ( PNS) resides or extends outside the Central nervous system (CNS which consists of the Brain and Spinal cord. [2]
Central nervous system
- See also: List of regions in the human brain
The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. Anatomical regions of the brain are listed vertically following hierarchies that are standard in Neuroanatomy. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected The CNS is contained within the dorsal cavity, with the brain within the cranial cavity, and the spinal cord in the spinal cavity. The human body consists of the following Body cavities: dorsal body cavity Cranial cavity, enclosed by the Skull and contains the The cranial cavity, or intracranial space, is the space formed inside the Skull. The spinal canal (or vertebral canal or spinal cavity) is the space in Vertebrae through which the Spinal cord passes The CNS is covered by the meninges. The meninges (singular meninx) is the system of membranes which envelops the Central nervous system. The brain is also protected by the skull, and the spinal cord is also protected by the vertebrae. The nervous system can be connected into many systems that can function together. The two systems are central nervous system (CNS) and the peripheral nervous system (PNS).
Peripheral nervous system
The PNS consists of all the other nervous structures that do not lie in the CNS. In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain In the Anatomy of the Brain of Vertebrates, the prosencephalon (or forebrain) is the Rostral -most (forward-most portion of the The telencephalon (tɛlɛnˈsɛfəlɒn cerebrum, or forebrain is the most Anterior or especially in humans most Dorsal region of the In Animal anatomy, the rhinencephalon is a part of the Brain involved with Olfaction. The la amygdalae ( Latin, also la corpus amygdaloideum, singular la amygdala, from Greek el αμυγδαλή grc-Latn amygdalē, 'almond' The hippocampus is a part of the Forebrain, located in the medial Temporal lobe. The neocortex ( Latin for "new Bark " or "new Rind " is a part of the Brain of Mammals It is the outer layer of The lateral ventricles are part of the Ventricular system of the Brain. The diencephalon (or interbrain is the region of the Brain that includes the Thalamus, Hypothalamus, Epithalamus, Prethalamus or The epithalamus is a dorsal posterior segment of the Diencephalon (a segment in the middle of the Brain also containing the Hypothalamus The thalamus (from Greek θάλαμος = room chamber, IPA= /ˈθæləməs/ is a pair and symmetric part of the brain The hypothalamus links the Nervous system to the Endocrine system via the Pituitary gland (hypophysis The subthalamus is a part of the Diencephalon. Anatomy During development the subthalamus is continuous with the Hypothalamus, but is separated by The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. The pineal gland (also called the pineal body, epiphysis cerebri, or epiphysis) is a small endocrine gland in the vertebrate Brain The third ventricle ( ventriculus tertius) is one of four connected fluid-filled cavities comprising the Ventricular system within the human Brain. The brain stem (or brainstem) is the lower part of the Brain, adjoining and structurally continuous with the Spinal cord. In biological anatomy the mesencephalon (or midbrain) comprises the Tectum (or corpora quadrigemini Tegmentum, the ventricular mesocoelia (or "iter" The tectum (Latin roof) is a region of the Brain, specifically the dorsal part of the Mesencephalon (midbrain The cerebral peduncle, by most classifications is everything in the Mesencephalon except the Tectum. Pretectum is a structure located in the Midbrain. It receives binocular input from the Eyes and is involved with the pupillary light reflex. The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains Cerebrospinal The rhombencephalon (or hindbrain) is a developmental categorization of portions of the Central nervous system in Vertebrates. The metencephalon is a developmental categorization of portions of the Central nervous system. The pons (sometimes pons Varolii after Costanzo Varolio) is a structure located on the Brain stem. The cerebellum ( Latin: "little brain" is a region of the Brain that plays an important role in the integration of sensory perception The myelencephalon is a developmental categorization of a portion of the Central nervous system. The medulla oblongata is the lower portion of the Brainstem. It deals with autonomic functions such as breathing and blood pressure The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected The peripheral nervous system ( PNS) resides or extends outside the Central nervous system (CNS which consists of the Brain and Spinal cord. The large majority of what are commonly called nerves (which are actually axonal processes of nerve cells) are considered to be PNS.
Microanatomy
The nervous system is, on a small scale, primarily made up of neurons. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information However, glial cells also play a major role. Glial cells, commonly called neuroglia or simply glia (Greek for "glue" are non- Neuronal cells that provide support and nutrition
Neurons
They are the core components of both the central nervous system & peripheral nervous system. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. The peripheral nervous system ( PNS) resides or extends outside the Central nervous system (CNS which consists of the Brain and Spinal cord. Neurons are sensors that send electric messages to the Central Nervous System which send the electric messages back to the neurons telling them how to react, where the messages are finally sent back directly to the brain. These messages travel at a usual pace of 100 meters per second.
Glial cells
Glial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system. Glial cells, commonly called neuroglia or simply glia (Greek for "glue" are non- Neuronal cells that provide support and nutrition Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Homeostasis (from Greek: ὅμος hómos, "equal" and ιστημι istēmi, "to stand" lit Myelin is an electrically-insulating Dielectric Phospholipid layer that surrounds only the Axons of many Neurons It is an outgrowth In the human brain, glia are estimated to outnumber neurons by about 10 to 1. The human brain controls the Central nervous system (CNS by way of the Cranial nerves and Spinal cord, the Peripheral nervous system (PNS [3]
Glial cells provide support and protection for neurons. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information They are thus known as the "glue" of the nervous system. The four main functions of glial cells are to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy pathogens and remove dead neurons. A nutrient is food or chemicals that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious
Physiological division
A less anatomical but much more functional division of the human nervous system is that classifying it according to the role that the different neural pathways play, regardless whether these cross through the CNS or the PNS:
The somatic nervous system is responsible for coordinating the body's movements, and also for receiving external stimuli. "Somatic" redirects here for the musician known as Somatic see Hahn Rowe. It is the system that regulates activities that are under conscious control.
Of digestion, it regulates from the esophagus to the stomach, small intestine and colon.
In turn, these pathways can be divided according to the direction in which they conduct stimuli:
- Afferent system by sensory neurons, which carry impulses from a receptor to the CNS
- Efferent system by motor neurons, which carry impulses from the CNS to an effector
- Relay system by relay neurons (also called interneurons), which transmit impulses between the sensory and motor neurones. Sensory neurons are Neurons that are activated by sensory input (vision touch hearing etc In Vertebrates the term motor neuron (or motoneuron) classically applies to Neurons located in the Central nervous system (or CNS that project An interneuron (also called association neuron, local circuit neuron or relay neuron) is a neuron which connects Afferent neurons and Efferent
However, there are relay neurons in the CNS as well.
The junction between two neurones is called a synapse. Chemical synapses are specialized junctions through which Neurons signal to each other and to non-neuronal cells such as those in Muscles or Glands There is a very narrow gap (about 20nm in width) between the neurons - the synaptic cleft, where an action potential is transmitted from one neuron to a neighboring one. Chemical synapses are specialized junctions through which Neurons signal to each other and to non-neuronal cells such as those in Muscles or Glands They do this by relaying the message with the use of neurotransmitters which the next neuron then receives the electrical signal, known as a nerve impulse. See Chemical synapse for an introduction to concepts and terminology used in this article In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal The nerve impulse is determined by the neurotransmitter to then carry the message to its appropriate destination. These nerve impulses are a change in ion balance in the nerve cell, which the central nervous system can then interpret. The fact that the nervous system uses a mixture of electrical and chemical signals makes it incredibly fast, which is necessary to acknowledge the presence of danger. For example, a hand touching a hot stove. If the nervous system was only comprised of chemical signals, the body would not tell the arm to move fast enough to escape dangerous burns. So the speed of the nervous system is a necessity for life.
| Physiological division | Somatic nervous system | Afferent system | ||
| Efferent system | ||||
| Autonomic nervous system | Sympathetic | Afferent system | ||
| Efferent system | ||||
| Parasympathetic | Afferent system | |||
| Efferent system | ||||
Development
Some landmarks of embryonic neural development include the birth and differentiation of neurons from stem cell precursors, the migration of immature neurons from their birthplaces in the embryo to their final positions, outgrowth of axons from neurons and guidance of the motile growth cone through the embryo towards postsynaptic partners, the generation of synapses between these axons and their postsynaptic partners, and finally the lifelong changes in synapses which are thought to underlie learning and memory. "Somatic" redirects here for the musician known as Somatic see Hahn Rowe. In the Nervous system, afferent neurons --otherwise known as sensory or receptor Neurons -carry nerve impulses from receptors or sense In the Nervous system, efferent nerves – otherwise known as motor or effector Neurons – carry nerve impulses away from the &trade The autonomic nervous system ( ANS) (or visceral nervous system) is the part of the Peripheral nervous system that acts as a Control The Sympathetic Nervous System ( SNS) is a branch of the Autonomic nervous system along with the Enteric nervous system and Parasympathetic nervous In the Nervous system, afferent neurons --otherwise known as sensory or receptor Neurons -carry nerve impulses from receptors or sense In the Nervous system, efferent nerves – otherwise known as motor or effector Neurons – carry nerve impulses away from the The parasympathetic Nervous system ( PSNS) is a division of the Autonomic nervous system (ANS along with the Sympathetic nervous system In the Nervous system, afferent neurons --otherwise known as sensory or receptor Neurons -carry nerve impulses from receptors or sense In the Nervous system, efferent nerves – otherwise known as motor or effector Neurons – carry nerve impulses away from the The study of neural development draws on both Neuroscience and Developmental biology to describe the cellular and molecular mechanisms by which complex Nervous An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular In Developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized Cell type. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information Stem cells are cells found in most if not all multi-cellular Organisms. Cellular migration is the movement of cells in the body to their proper position An axon or nerve fiber is a long slender projectionof a nerve cell or Neuron, that conducts electrical impulses away from the neuron's Cell Axon guidance (also called axon pathfinding) is a subfield of Neural development concerning the process by which Neurons send out Axons to reach A growth cone is a dynamic Actin -supported extension of a developing Axon seeking its synaptic target Chemical synapses are specialized junctions through which Neurons signal to each other and to non-neuronal cells such as those in Muscles or Glands In Neuroscience, synaptic plasticity is the ability of the connection or Synapse, between two Neurons to change in strength.
Importance
Many people have lost basic motor skills and other skills because of spinal cord injuries. If this portion is damaged, the biggest nerve and the most important one gets damaged. This leads to paralysis or other permanent damage.
Abilities
The nervous system is able to make basic motor skills and other skills possible. The basic 5 senses of texture, taste, sight, smell, and hearing are powered by the nervous system. Senses are the physiological methods of Perception. The senses and their operation classification and theory are overlapping topics studied by a variety of fields If disabled, basic motor skills may be lost.
Non-humans
Vertebrates
The nervous system of all vertebrate animals, is often divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord.
Worms
Planaria, a type of flatworm, have dual nerve cords running along the length of the body and merging at the tail and the mouth. Planaria are nonparasitic Flatworms (which make great pets of the biological family Planariidae, belonging to the order Seriata. The flatworms (Phylum Platyhelminthes from the Greek πλατύ platy, meaning "flat" and ἕλμινς (root ἑλμινθ- helminth- The ventral nerve cords make up the Nervous system of some phyla of the Invertebrates particularly within the Nematodes Annelids and These nerve cords are connected by transverse nerves like the rungs of a ladder. These transverse nerves help coordinate the two sides of the animal. In Mathematics and its applications a coordinate system is a system for assigning an n - Tuple of Numbers or scalars to each point Two large ganglia at the head end function similar to a simple brain. In Anatomy, a ganglion (pl ganglia) is a tissue mass. Neurology In neurological contexts ganglia are composed mainly of Photoreceptors on the animal's eyespots provide sensory information on light and dark. Photoreceptor can refer to In anatomy/cell biology Photoreceptor cell: a photosensitive cell most commonly referring to a specialized type of neuron
The nervous system of the roundworm Caenorhabditis elegans has been mapped out to the cellular level. The nematodes or roundworms ( Phylum Nematoda from Greek (nema "thread" + -ode "like" are one of the most common Caenorhabditis elegans (ˌsiːnoʊræbˈdaɪtɪs ˈɛlɪgænz is a free-living Nematode (roundworm about 1 mm in length which Every neuron and its cellular lineage has been recorded and most, if not all, of the neural connections are known. Fate mapping is a technique that is used to show how a cell or tissue moves and what it will become during normal development In this species, the nervous system is sexually dimorphic; the nervous systems of the two sexes, males and hermaphrodites, have different numbers of neurons and groups of neurons that perform sex-specific functions. Sexual dimorphism is the systematic difference in form between individuals of different Sex in the same Species. A hermaphrodite is an organism having both male and female reproductive organs In C. elegans, males have exactly 383 neurons, while hermaphrodites have exactly 302 neurons [1]
Arthropoda
Arthropods, such as insects and crustaceans, have a nervous system made up of a series of ganglia, connected by a ventral nerve cord made up of two parallel connectives running along the length of the belly [2]. Arthropods are Animals belonging to the Phylum Arthropoda (from Greek ἄρθρον arthron, " Joint " Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting In Anatomy, a ganglion (pl ganglia) is a tissue mass. Neurology In neurological contexts ganglia are composed mainly of The ventral nerve cords make up the Nervous system of some phyla of the Invertebrates particularly within the Nematodes Annelids and Typically, each body segment has one ganglion on each side, though some ganglia are fused to form the brain and other large ganglia [3]. In Anatomy, a ganglion (pl ganglia) is a tissue mass. Neurology In neurological contexts ganglia are composed mainly of
The head segment contains the brain, also known as the supraesophageal ganglion. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain In the insect nervous system, the brain is anatomically divided into the protocerebrum, deutocerebrum, and tritocerebrum. Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Immediately behind the brain is the subesophageal ganglion, which is composed of three pairs of fused ganglia. Insects The subesophageal ganglion of insects is composed of three pairs of fused Ganglia. It controls the mouthparts, the salivary glands and certain muscles. The mouthparts of Arthropods have evolved into a number of forms each adapted to a different style or mode of feeding The salivary glands in mammals are exocrine glands that produce saliva Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the
Many arthropods have well-developed sensory organs, including compound eyes for vision and antennae for olfaction and pheromone sensation. Senses are the physiological methods of Perception. The senses and their operation classification and theory are overlapping topics studied by a variety of fields Antennae (singular antenna) are paired Appendages connected to the front-most segments of Arthropods In Crustaceans they are Olfaction (also known as olfactics or smell) refers to the Sense of smell. A pheromone (from Greek φέρω phero "to bear" + ‘ορμόνη " Hormone " is a Chemical that triggers a natural The sensory information from these organs is processed by the brain.
Development
Neural development in most species have many similarities neural development in humans. The study of neural development draws on both Neuroscience and Developmental biology to describe the cellular and molecular mechanisms by which complex Nervous The study of neural development draws on both Neuroscience and Developmental biology to describe the cellular and molecular mechanisms by which complex Nervous
References
- ^ "Nervous System". Columbia Encyclopedia. Columbia University Press. Retrieved on 4/1/08.
- ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall, 132-144. ISBN 0-13-981176-1.
- ^ sfn.org Society for Neuroscience, 2000
External links
- Neuroscience for Kids
- The Human Brain Project Homepage
- Kimball's Biology Pages, CNS
- Kimball's Biology Pages, PNS
en:Nervous system
Dictionary
nervous system
-noun
- (neuroanatomy) The system which coordinates the activity of the muscles, monitors the organs, constructs and processes input from the senses, and initiates actions. In vertebrates it consists of the brain, the brainstem, the spinal cord, nerves, and ganglia.
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