A report on Nervous system

The human nervous system
Diagram showing the major divisions of the vertebrate nervous system.
Horizontal section of the head of an adult female human, showing skin, skull, and brain with gray matter (brown in this image) and underlying white matter
Nervous system of a bilaterian animal, in the form of a nerve cord with segmental enlargements, and a "brain" at the front
Area of the human body surface innervated by each spinal nerve
Earthworm nervous system. Top: side view of the front of the worm. Bottom: nervous system in isolation, viewed from above
Internal anatomy of a spider, showing the nervous system in blue
Major elements in synaptic transmission. An electrochemical wave called an action potential travels along the axon of a neuron. When the wave reaches a synapse, it provokes release of a small amount of neurotransmitter molecules, which bind to chemical receptor molecules in the membrane of the target cell.
Illustration of pain pathway, from René Descartes's Treatise of Man
Simplified schema of basic nervous system function: signals are picked up by sensory receptors and sent to the spinal cord and brain, where processing occurs that results in signals sent back to the spinal cord and then out to motor neurons
Layers protecting the brain and spinal cord.

Highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body.

- Nervous system
The human nervous system

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The brain of a common chimpanzee

Brain

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The brain of a common chimpanzee
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Neurons generate electrical signals that travel along their axons. When a pulse of electricity reaches a junction called a synapse, it causes a neurotransmitter chemical to be released, which binds to receptors on other cells and thereby alters their electrical activity.
Nervous system of a generic bilaterian animal, in the form of a nerve cord with segmental enlargements, and a "brain" at the front.
Fruit flies (Drosophila) have been extensively studied to gain insight into the role of genes in brain development.
The brain of a shark.
The main subdivisions of the embryonic vertebrate brain (left), which later differentiate into structures of the adult brain (right).
The main anatomical regions of the vertebrate brain, shown for shark and human. The same parts are present, but they differ greatly in size and shape.
Brain of a human embryo in the sixth week of development.
Brain electrical activity recorded from a human patient during an epileptic seizure.
Model of a neural circuit in the cerebellum, as proposed by James S. Albus.
Diagram of signal processing in the auditory system.
Cross-section of a human head, showing location of the hypothalamus.
Components of the basal ganglia, shown in two cross-sections of the human brain. Blue: caudate nucleus and putamen. Green: globus pallidus. Red: subthalamic nucleus. Black: substantia nigra.
The Human Brain Project is a large scientific research project, starting in 2013, which aims to simulate the complete human brain.
Design of an experiment in which brain activity from a monkey was used to control a robotic arm.
Illustration by René Descartes of how the brain implements a reflex response.
Andreas Vesalius' Fabrica, published in 1543, showing the base of the human brain, including optic chiasma, cerebellum, olfactory bulbs, etc.
Drawing by Santiago Ramón y Cajal of two types of Golgi-stained neurons from the cerebellum of a pigeon.
Gulai otak, beef brain curry from Indonesia

A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.

Schematic diagram showing the central nervous system in yellow, peripheral in orange

Central nervous system

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Schematic diagram showing the central nervous system in yellow, peripheral in orange
Dissection of a human brain with labels showing the clear division between white and gray matter.
Diagram of the columns and of the course of the fibers in the spinal cord. Sensory synapses occur in the dorsal spinal cord (above in this image), and motor nerves leave through the ventral (as well as lateral) horns of the spinal cord as seen below in the image.
Different ways in which the CNS can be activated without engaging the cortex, and making us aware of the actions. The above example shows the process in which the pupil dilates during dim light, activating neurons in the spinal cord. The second example shows the constriction of the pupil as a result of the activation of the Eddinger-Westphal nucleus (a cerebral ganglion).
A map over the different structures of the nervous systems in the body, showing the CNS, PNS, autonomic nervous system, and enteric nervous system.
Schematic image showing the locations of a few tracts of the spinal cord.
Reflexes may also occur without engaging more than one neuron of the CNS as in the below example of a short reflex.
Diagram depicting the main subdivisions of the embryonic vertebrate brain, later forming forebrain, midbrain and hindbrain.
Development of the neural tube

The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord.

An axon of a multipolar neuron

Axon

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Long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action potentials away from the nerve cell body.

Long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action potentials away from the nerve cell body.

An axon of a multipolar neuron
A typical myelinated axon
A dissected human brain, showing grey matter and white matter
Detail showing microtubules at axon hillock and initial segment.
TEM of a myelinated axon in cross-section.
Cross section of an axon: (1) Axon (2) Nucleus 
(3) Schwann cell (4) Myelin sheath (5) Neurilemma
(A) pyramidal cell, interneuron, and short durationwaveform (Axon), overlay of the three average waveforms;
(B) Average and standard error of peak-trough time for pyramidal cells interneurons, and putative axons;
(C) Scatter plot of signal to noise ratios for individual units againstpeak-trough time for axons, pyramidal cells (PYR) and interneurons (INT).
Axon of nine-day-old mouse with growth cone visible

Axons are the primary transmission lines of the nervous system, and as bundles they form nerves.

Drawing by Santiago Ramón y Cajal (1899) of neurons in the pigeon cerebellum

Neuroscience

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Drawing by Santiago Ramón y Cajal (1899) of neurons in the pigeon cerebellum
Illustration from Gray's Anatomy (1918) of a lateral view of the human brain, featuring the hippocampus among other neuroanatomical features
The Golgi stain first allowed for the visualization of individual neurons.
Human nervous system
Photograph of a stained neuron in a chicken embryo
Proposed organization of motor-semantic neural circuits for action language comprehension. Adapted from Shebani et al. (2013)
Parasagittal MRI of the head of a patient with benign familial macrocephaly

Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system) and its functions.

Illustration of the four different types of glial cells found in the central nervous system: ependymal cells (light pink), astrocytes (green), microglial cells (dark red), and oligodendrocytes (light blue).

Glia

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Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses.

Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses.

Illustration of the four different types of glial cells found in the central nervous system: ependymal cells (light pink), astrocytes (green), microglial cells (dark red), and oligodendrocytes (light blue).
Neuroglia of the brain shown by Golgi's method
Astrocytes can be identified in culture because, unlike other mature glia, they express glial fibrillary acidic protein (GFAP)
Glial cells in a rat brain stained with an antibody against GFAP
Different types of neuroglia
23-week fetal brain culture astrocyte
Neoplastic glial cells stained with an antibody against GFAP (brown), from a brain biopsy

The term derives from Greek γλία and γλοία "glue" ( or ), and suggests the original impression that they were the glue of the nervous system.

Sensation consists of signal collection and transduction

Sense

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Biological system used by an organism for sensation, the process of gathering information about the world and responding to stimuli.

Biological system used by an organism for sensation, the process of gathering information about the world and responding to stimuli.

Sensation consists of signal collection and transduction
Human power exponents and Steven's Power Law
Philippe Mercier - 
The Sense of Taste - Google Art Project
The sense of smell Bequest of Mrs E.G. Elgar, 1945 Museum of New Zealand Te Papa Tongarewa.
Lairesse's
Detail of The Senses of Hearing, Touch and Taste, Jan Brueghel the Elder, 1618
In this painting by Pietro Paolini, each individual represents one of the five senses.

The nervous system calculates a criterion, or an internal threshold, for the detection of a signal in the presence of noise.

Human brain and skull

Human brain

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Human brain and skull
Human brain (sagittal section)
MRI scan of a human individual's brain
Major gyri and sulci on the lateral surface of the cortex
Lobes of the brain
Cortical folds and white matter in horizontal bisection of head
Human brain viewed from below, showing cerebellum and brainstem
Cerebrospinal fluid circulates in spaces around and within the brain
Two circulations joining at the circle of Willis (inferior view).
Diagram showing features of cerebral outer membranes and supply of blood vessels
Neurulation and neural crest cells
Primary and secondary vesicle stages of development in the early embryo to the fifth week
Brain of a human embryo in the sixth week of development
Motor and sensory regions of the brain
Cortical areas
Routing of neural signals from the two eyes to the brain
Broca's area and Wernicke's area are linked by the arcuate fasciculus.
PET image of the human brain showing energy consumption
CT scan of a cerebral hemorrhage, showing an intraparenchymal bleed (bottom arrow) with surrounding edema (top arrow)
The skull of Phineas Gage, with the path of the iron rod that passed through it without killing him, but altering his cognition. The case helped to convince people that mental functions were localized in the brain.
Phrenology summarized in an 1883 chart
Hieroglyph for the word "brain" (c.1700 BC)
Drawing of the base of the brain, from Andreas Vesalius's 1543 work De humani corporis fabrica
One of Leonardo da Vinci's sketches of the human skull
Drawing by Camillo Golgi of vertical section of rabbit hippocampus, from his "Sulla fina anatomia degli organi centrali del sistema nervoso", 1885
Drawing of cells in chick cerebellum by Santiago Ramón y Cajal, from "Estructura de los centros nerviosos de las aves", Madrid, 1905

The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system.

The human nervous system. Sky blue is PNS; yellow is CNS.

Peripheral nervous system

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The human nervous system. Sky blue is PNS; yellow is CNS.
3D Medical Animation still shot of Lumbosacral Plexus

The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS).

Nerves (yellow) in the arm

Nerve

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Enclosed, cable-like bundle of nerve fibers in the peripheral nervous system.

Enclosed, cable-like bundle of nerve fibers in the peripheral nervous system.

Nerves (yellow) in the arm
Cross-section of a nerve
Micrograph demonstrating perineural invasion of prostate cancer. H&E stain.

The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body.

Cnidaria

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Phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.

Phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.

Pacific sea nettles, Chrysaora fuscescens
Oral end of actinodiscus polyp
Firing sequence of the cnida in a hydra's nematocyst Operculum (lid) "Finger" that turns inside out / / / Barbs  Venom  Victim's skin  Victim's tissues
A hydra's nematocyst, before firing. "trigger" cilium
Stranded scyphozoans on a Cambrian tidal flat in Blackberry Hill, Wisconsin.
The fossil coral Cladocora from Pliocene rocks in Cyprus
Illustrated tree of cnidarians and their closest relatives
The dangerous Carukia barnesi, one of the known species of box jellyfish which can cause Irukandji syndrome.
Cerianthus filiformis (Ceriantharia)
Sea anemones (Actinaria, part of Hexacorallia)
Coral Acropora muricata (Scleractinia, part of Hexacorallia)
Sea fan Gorgonia ventalina (Alcyonacea, part of Octocorallia)
Box jellyfishCarybdea branchi (Cubozoa)
Siphonophore Physalia physalis (Hydrozoa)
Myxobolus cerebralis (Myxozoa)
Polypodium hydriforme (Polypodiozoa)
Jellyfish Phyllorhiza punctata (Scyphozoa)
Stalked jelly Haliclystus antarcticus (Staurozoa)

Both cnidarians and ctenophores are more complex than sponges as they have: cells bound by inter-cell connections and carpet-like basement membranes; muscles; nervous systems; and some have sensory organs.