| Ganglion cell | |
|---|---|
 Various forms of nerve cells.
| |
| Details | |
| Location | Varies by type |
| Shape | Varies |
| Function | Varies but often excitatory projection |
| Neurotransmitter | Varies but often glutamate |
| Anatomical terms of neuroanatomy | |
| Ganglion cell | |
|---|---|
| Various forms of nerve cells.
| |
| Details | |
| Location | Varies by type |
| Shape | Varies |
| Function | Varies but often excitatory projection |
| Neurotransmitter | Varies but often glutamate |
| Anatomical terms of neuroanatomy | |
In neurophysiology, a ganglion cell is a cell found in a ganglion (a cluster of neurons in the peripheral nervous system). Examples of ganglion cells include:
During the late 1800s, early 1900s, Spanish Neuroscientist and Pathologist Santiago Ramón y Cajal proposed Neuron theory which basically introduced the idea that the Nervous system contained cells called the Neuron. The process he used was called Golgi staining of the vertebrae retina. Cajal was able to differentiate between different types of Ganglion cell based on dendritic morphology, cell body and dendritic tree size, and number of sub layers in which they arborize/stratification layers. Through this study, he discovered that the ganglion cell distribution amongst vertebrates were pretty similar minus the Rods and cones in the retinas. [3]
In the 1940s, American Neurologist Stephen Polyak [4] produced description of the Golgi-impregnated Cells that helped further classify types of Ganglion Cells. This data helped scientists get a better understanding of the ganglion cells present in the retinas of Mammals and Primates [3]
In 1974, Boycott and Wassle created a scheme for the classification of Ganglion Cells that was found to be in the cat retina. These cells, alpha, beta, delta and gamma are seen to be linked with the X,Y and W types of physiology. Boycott and Wassle confirmed the idea of Cajal's Ox and Dog retina idea by naming the alpha and beta.
In 1978, the idea of the alpha and beta ganglion cells could be divided into different subgroups, sublamina a and sublamina b. Sublamina a contains dendrite cells containing OFF-center receptive fields while the Sublamina b contains On-center receptive fields. [3] [5]
Glaucoma: Glaucoma is a collection of diseases that damages the nerve in the eye / retina. The damage in the nerve has the possibility to cause blindness. You may not know you have a Glaucoma without an in-depth eye exam normally using the dilation method. There is no cure for a Glaucoma, but it may be treated if found early. It is unknown the cause of a Glaucoma, but those who may be at risk include:
Hereditary optic neuroretinopathy: There are two different types of Hereditary Optic Neuroretinopathy, those including Leber's hereditary optic neuropathy and Autosomal Dominant Optic Atrophy. The Leber's Neuropathy is caused by a mutation in the Mitochondrial DNA (the DNA located inside the chromosome) This is only obtainable through the mother. Some individuals are carriers and experience no symptoms. Symptoms of individuals who are affected by Leber's Neuropathy include:
Autosomal Dominant Optic Atrophy is a mutated gene in the autosomes (not sex-linked genes in humans chromosome pairs 1-22). This trait is present in anyone with the mutation in the autosome. The individual only needs one mutated gene to be affected. Symptoms of this condition include:
These diseases can be examined by tests such as Eye exams, Image testing and a look through family history. [8]
Parkinson's disease: Parkinson's Disease is a condition that originates in the Nervous System and affects parts controlled by the nervous system. This disease is progressive, meaning it progressively gets worse overtime. A slow loss of Retinal Ganglion Cells may be observed overtime. List of symptoms include:
Those who are at risk include genes (through family members), toxins from the environment, and the presence of Lewy bodies. [9] [10] [11]
The retina is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception. The retina serves a function which is in many ways analogous to that of the film or image sensor in a camera.
In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, 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; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.
The visual system is the physiological basis of visual perception. The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment. The visual system is associated with the eye and functionally divided into the optical system and the neural system.
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential.
This is a partial list of human eye diseases and disorders.
A retinal ganglion cell (RGC) is a type of neuron located near the inner surface of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and retina amacrine cells. Retina amacrine cells, particularly narrow field cells, are important for creating functional subunits within the ganglion cell layer and making it so that ganglion cells can observe a small dot moving a small distance. Retinal ganglion cells collectively transmit image-forming and non-image forming visual information from the retina in the form of action potential to several regions in the thalamus, hypothalamus, and mesencephalon, or midbrain.
The visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction"; in ophthalmology and neurology the emphasis is mostly on the structure inside the visual field and it is then considered “the field of functional capacity obtained and recorded by means of perimetry”.
The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye.
Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors, inner retinal cells, and the ganglion cells. Electrodes are placed on the surface of the cornea or on the skin beneath the eye to measure retinal responses. Retinal pigment epithelium (RPE) responses are measured with an EOG test with skin-contact electrodes placed near the canthi. During a recording, the patient's eyes are exposed to standardized stimuli and the resulting signal is displayed showing the time course of the signal's amplitude (voltage). Signals are very small, and typically are measured in microvolts or nanovolts. The ERG is composed of electrical potentials contributed by different cell types within the retina, and the stimulus conditions can elicit stronger response from certain components.
Leber's hereditary optic neuropathy (LHON) is a mitochondrially inherited degeneration of retinal ganglion cells (RGCs) and their axons that leads to an acute or subacute loss of central vision; it predominantly affects young adult males. LHON is transmitted only through the mother, as it is primarily due to mutations in the mitochondrial genome, and only the egg contributes mitochondria to the embryo. Men cannot pass on the disease to their offspring. LHON is usually due to one of three pathogenic mitochondrial DNA (mtDNA) point mutations. These mutations are at nucleotide positions 11778 G to A, 3460 G to A and 14484 T to C, respectively in the ND4, ND1 and ND6 subunit genes of complex I of the oxidative phosphorylation chain in mitochondria.
Neuro-ophthalmology is an academically-oriented subspecialty that merges the fields of neurology and ophthalmology, often dealing with complex systemic diseases that have manifestations in the visual system. Neuro-ophthalmologists initially complete a residency in either neurology or ophthalmology, then do a fellowship in the complementary field. Since diagnostic studies can be normal in patients with significant neuro-ophthalmic disease, a detailed medical history and physical exam is essential, and neuro-ophthalmologists often spend a significant amount of time with their patients.
Intrinsically photosensitive retinal ganglion cells (ipRGCs), also called photosensitive retinal ganglion cells (pRGC), or melanopsin-containing retinal ganglion cells (mRGCs), are a type of neuron in the retina of the mammalian eye. The presence of an additional photoreceptor was first suspected in 1927 when mice lacking rods and cones still responded to changing light levels through pupil constriction; this suggested that rods and cones are not the only light-sensitive tissue. However, it was unclear whether this light sensitivity arose from an additional retinal photoreceptor or elsewhere in the body. Recent research has shown that these retinal ganglion cells, unlike other retinal ganglion cells, are intrinsically photosensitive due to the presence of melanopsin, a light-sensitive protein. Therefore, they constitute a third class of photoreceptors, in addition to rod and cone cells.
Leber congenital amaurosis (LCA) is a rare inherited eye disease that appears at birth or in the first few months of life.
Dominant optic atrophy (DOA), or autosomal dominant optic atrophy (ADOA), (Kjer's type) is an autosomally inherited disease that affects the optic nerves, causing reduced visual acuity and blindness beginning in childhood. However, the disease can seem to re-present a second time with further vision loss due to the early onset of presbyopia symptoms (i.e., difficulty in viewing objects up close). DOA is characterized as affecting neurons called retinal ganglion cells (RGCs). This condition is due to mitochondrial dysfunction mediating the death of optic nerve fibers. The RGCs axons form the optic nerve. Therefore, the disease can be considered of the central nervous system. Dominant optic atrophy was first described clinically by Batten in 1896 and named Kjer’s optic neuropathy in 1959 after Danish ophthalmologist Poul Kjer, who studied 19 families with the disease. Although dominant optic atrophy is the most common autosomally inherited optic neuropathy (i.e., disease of the optic nerves), it is often misdiagnosed.
Oncomodulin is a parvalbumin-family calcium-binding protein expressed and secreted by macrophages.
Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain.
A bipolar neuron, or bipolar cell, is a type of neuron characterized by having both an axon and a dendrite extending from the soma in opposite directions. These neurons are predominantly found in the retina and olfactory system. The embryological period encompassing weeks seven through eight marks the commencement of bipolar neuron development.
Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline bodies.
The Vision Institute is a research center in the Quinze-Vingts National Eye Hospital in Paris, France. It is one of several such centers in Europe on eye diseases.
Alfredo Arrigo Sadun is an American ophthalmologist, academic, author and researcher. He holds the Flora L. Thornton Endowed Chair at Doheny Eye Centers-UCLA and is Vice-Chair of Ophthalmology at UCLA.
