Information: - The retina (, , pl. retinae, ; from Latin "rte", meaning "net") is the third and inner coat of the eye which is a light-sensitive layer of tissue. The optics of the eye create an image of the visual world on the retina (through the cornea and lens), which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These are sent to various visual centres of the brain through the fibres of the optic nerve. Neural retina typically refers to three layers of neural cells (photo receptor cells, bipolar cells, and ganglion cells) within the retina, while the entire retina refers to these three layers plus a layer of pigmented epithelial cells. - The nervous system is the part of an animal's body that coordinates its actions and transmits signals to and from different parts of its body. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrate species it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called "motor" or "efferent" nerves, while those nerves that transmit information from the body to the CNS are called "sensory" or "afferent". Most nerves serve both functions and are called "mixed" nerves. The PNS is divided into a) somatic and b) autonomic nervous system, and c) the enteric nervous system. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves. - The central nervous system (CNS) is the part of the nervous system consisting of the brain and spinal cord. The central nervous system is so named because it integrates information it receives from, and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric animalsthat is, all multicellular animals except sponges and radially symmetric animals such as jellyfishand it contains the majority of the nervous system. Many consider the retina and the optic nerve (2nd cranial nerve), as well as the olfactory nerves (1st) and olfactory epithelium as parts of the CNS, synapsing directly on brain tissue without intermediate ganglia. Following this classification the olfactory epithelium is the only central nervous tissue in direct contact with the environment, which opens up for therapeutic treatments. - The optic nerve, also known as cranial nerve II, is a paired nerve that transmits visual information from the retina to the brain. The optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells. In humans, the optic nerve extends from the optic disc to the optic chiasm and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus. Structure. The optic nerve is the second of twelve paired cranial nerves and is technically part of the central nervous system, rather than the peripheral nervous system because it is derived from an out-pouching of the diencephalon (optic stalks) during embryonic development. As a consequence, the fibers of the optic nerve are covered with myelin produced by oligodendrocytes, rather than Schwann cells of the peripheral nervous system, and are encased within the meninges. Peripheral neuropathies like GuillainBarre syndrome do not affect the optic nerve. However, most typically the optic nerve is grouped with the other eleven cranial nerves and considered to be part of the peripheral nervous system. - The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the sensory organs for senses such as vision. The brain is the most complex organ in a vertebrate's body. In a human, the cerebral cortex contains approximately 1533 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells. - A nerve is an enclosed, cable-like bundle of axons (nerve fibers, the long and slender projections of neurons) in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs. - Radial glial cells are bipolar - shaped cells that span the width of the cortex in the developing central nervous system ( CNS ) and serve as primary progenitors capable of generating neurons , astrocytes , and oligodendrocytes . During development , newborn neurons use radial glia as scaffolds , traveling along the radial glial fibers in order to reach their final destinations . Despite the various possible fates of the radial glial population , it has been demonstrated through clonal analysis that most radial glia have restricted , unipotent or multipotent , fates . Radial glia can be found during the neurogenic phase in all vertebrates ( studied to date ) . The term '' radial glia '' refers to the morphological characteristics of these cells that were first observed : namely , their radial processes and their similarity to astrocytes , another member of the glial cell family . - Oligodendrocytes (from Greek, meaning "cells with a few branches"), or oligodendroglia (Greek, "few tree glue"), are a type of neuroglia. Their main functions are to provide support and insulation to axons in the central nervous system of some vertebrates, equivalent to the function performed by Schwann cells in the peripheral nervous system. Oligodendrocytes do this by creating the myelin sheath, which is 80% lipid and 20% protein. A single oligodendrocyte can extend its processes to 50 axons, wrapping approximately 1m of myelin sheath around each axon; Schwann cells, on the other hand, can wrap around only one axon. Each oligodendrocyte forms one segment of myelin for several adjacent axons. - The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The brain and spinal cord together make up the central nervous system (CNS). The spinal cord begins at the occipital bone and extends down to the space between the first and second lumbar vertebrae; it does not extend the entire length of the vertebral column. It is around in men and around long in women. Also, the spinal cord has a varying width, ranging from thick in the cervical and lumbar regions to thick in the thoracic area. The enclosing bony vertebral column protects the relatively shorter spinal cord. The spinal cord functions primarily in the transmission of neural signals between the brain and the rest of the body but also contains neural circuits that can independently control numerous reflexes and central pattern generators. The spinal cord has three major functions: as a conduit for motor information, which travels down the spinal cord, as a conduit for sensory information in the reverse direction, and finally as a center for coordinating certain reflexes. - The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. In humans, it measures about 9 cm (3 centimeters by 3 centimeters) and lies on the roof of the nasal cavity about 7cm above and behind the nostrils. The olfactory epithelium is the part of the olfactory system directly responsible for detecting odors. - Jellyfish or jellies are softbodied, free-swimming aquatic animals with a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate to acquire propulsion and locomotion. The tentacles may be utilized to capture prey or defend against predators by emitting toxins in a painful sting. Jellyfish species are classified in the subphylum Medusozoa which makes up a major part of the phylum Cnidaria, although not all Medusozoa species are considered to be jellyfish. - Sponges are the basalmost clade of animals of the phylum Porifera (meaning "pore bearer". They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. Sponges have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes. Overview. Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues and organs, and have no body symmetry. The shapes of their bodies are adapted for maximal efficiency of water flow through the central cavity, where it deposits nutrients, and leaves through a hole called the osculum. Many sponges have internal skeletons of spongin and/or spicules of calcium carbonate or silicon dioxide. All sponges are sessile aquatic animals. Although there are freshwater species, the great majority are marine (salt water) species, ranging from tidal zones to depths exceeding . - The olfactory nerve is typically considered the first cranial nerve, or simply CN I, that contains sensory nerve fibres relating to smell. Given the information, choose the subject and object entities that have the relation of 'subclass of'.
radial glial cell , neuroglia