151 Sentences With "nerve fiber" | Random Sentence Generator

The sensor attached to a nerve fiber in a rat.

Another clue of the disease is thin retinal nerve fiber layers (RNFL).

In fact, participants with a low test score on any one cognitive test had thinner retinal nerve fiber layers.

Eye exams for all of the kids found they had an average retinal nerve fiber thickness of 104 micrometers.

"However, a thinner retinal nerve fiber layer has been connected to a higher risk of development of glaucoma," Leung added.

In low birth weight children, average retinal nerve fiber was 3.5 micrometers thinner than with kids born at a normal weight.

The differences in retinal nerve fiber layer thickness found in the study aren't big enough to produce detectable eye problems, Leung said by email.

A quick survey of the research being done includes considerations of reporting bias and playing style, but also extends to hormonal differences, neck strength, and nerve fiber structure.

When the retinal nerve fiber layer is too thin, people may have an increased risk of vision impairment and glaucoma, an eye disease that can lead to blindness.

Children of mothers who smoked during pregnancy had retinal nerve fiber that was typically 5.7 micrometers thinner than in kids whose mothers didn't smoke at all while pregnant.

They also explain how women with PCOS, like these astronauts, have higher levels of homocysteine, altered hormone levels, a thicker retinal nerve fiber layer, intracranial hypertension, the list goes on.

This conclusion could be related to the study's curious postflight findings concerning white matter, a brain tissue coated in a lipid called myelin that increases the speed of nerve fiber impulses.

Researchers focused on the thickness of what's known as the retinal nerve fiber layer, made of fibers in the optic nerve that transmit visual information from the eye to the brain.

In the current study, researchers examined data from eye exams on 1,23 children at age 11 or 12 and found both smoking and low birth weight independently associated with thinner retinal nerve fiber.

CRADLE also helped detect myelin retinal nerve fiber layer (MRNFL), a condition in which a myelin sheath around the eyeball affects the retina and diminishes sight capability, in Lee Gordon's daughter, Catherina, now 6.

In fresh research, Dr. Fang Ko of the UCL Institute of Ophthalmology in London explored the thickness of the retinal nerve fiber layer as a possible predictor of memory loss and other mental failings.

Because low birth weight is also associated with having a thinner retinal nerve fiber layer, smoking could have a direct and indirect effect on the optic nerve and its connections to the retina, researchers note.

Clinical Interpretation based on results from GDx Nerve Fiber Analyzer from Carl Zeiss Meditec. Firstly, this instrument is used to measure thickness of nerve fiber layer in our retina. But, GDx give monochromatic image. Then this system will analyze and give colors for certain various thicknesses.

Specific terms are used for peripheral nerves that originate from, or arrive at, a specific point. An afferent nerve fiber is a fibre originating at the present point. For example, a striatal afferent is an afferent originating at the striatum. An efferent nerve fiber is one that arrives at the present point.

This has future applications for monitoring glaucoma patients who either have changes in nerve fiber layer thickness or alterations in vasculature from damage to the retina.Scoles D, Gray DC, Hunter JJ, Wolfe R, Gee BP, Geng Y, et al. "In vivo imaging of retinal nerve fiber layer vasculature: imaging histology comparison". BMC Ophthalmol. 2009;9:9.

At the center of each Grandry corpuscle is the terminal end of an afferent nerve fiber. A single nerve fiber enters each corpuscle and becomes unmyelinated a short distance into the capsule. This fiber can be one of several branches from a single nerve axon that innervates multiple Grandry corpuscles. The unmyelinated nerve then flattens into a wide disc containing many mitochondria.

The GDx nerve fiber analyzers measure the retinal nerve fiber layer (RNFL) thickness with a scanning laser polarimeter based on the birefringent properties of the RNFL. Measurement is obtained from a band 1.75 disc diameters concentric to the disc. It projects a polarized beam of a light into the eye. As this light passes through the NFL tissue, it changes and slow.

However, the myelin layer does not ensure a perfect regeneration of the nerve fiber. Some regenerated nerve fibers do not find the correct muscle fibers, and some damaged motor neurons of the peripheral nervous system die without regrowth. Damage to the myelin sheath and nerve fiber is often associated with increased functional insufficiency. Unmyelinated fibers and myelinated axons of the mammalian central nervous system do not regenerate.

The name Inocybe means "fibrous hat". It is taken from the Greek words ἴς (in the genitive ἴνος, meaning “muscle, nerve, fiber, strength, vigor”) and κύβη (“head”).

Oligodendrocytes are found in the CNS and resemble an octopus: they have bulbous cell bodies with up to fifteen arm-like processes. Each process reaches out to an axon and spirals around it, creating a myelin sheath. The myelin sheath insulates the nerve fiber from the extracellular fluid and speeds up signal conduction along the nerve fiber. In the peripheral nervous system, Schwann cells are responsible for myelin production.

C fibers are one class of nerve fiber found in the nerves of the somatic sensory system. They are afferent fibers, conveying input signals from the periphery to the central nervous system.

Nerve fiber innervation is much denser for inner hair cells than for outer hair cells. A single inner hair cell is innervated by numerous nerve fibers, whereas a single nerve fiber innervates many outer hair cells. Inner hair cell nerve fibers are also very heavily myelinated, which is in contrast to the unmyelinated outer hair cell nerve fibers. The region of the basilar membrane supplying the inputs to a particular afferent nerve fibre can be considered to be its receptive field.

Based upon the data presented in In addition to inhibiting neural excitability, it has been observed that preceding an electrical stimulus with a depolarizing prepulse allows one to invert the current-distance relationship controlling nerve fiber recruitment, where the current-distance relationship describes how the threshold current for nerve fiber excitation is proportional to the square of the distance between the nerve fiber and the electrode. Therefore, if the region of influence for the depolarizing prepulse is less than that for the stimulus, the nerve fibers closer to the electrode will experience a greater increase in their threshold current for excitation. Thus, provided such a stimulus, the nerve fibers closest to the electrode may be inhibited, while those further away may be excited. A simulation of this stimulation, constructed by Drs.

5\. Saurabh K, Roy R, Mishra S, Garg B, Goel S. Multicolor imaging features of dissociated optic nerve fiber layer after internal limiting membrane peeling. Indian journal of ophthalmology. 2018 Dec 1;66(12):1853.

There is mild anterior uveitis. A cherry-red spot may be seen in the macula, along with cotton-wool spots elsewhere, due to retinal nerve fiber layer hemorrhages. The retinal arteries may show spontaneous pulsations.

An internodal segment (or internode) is the portion of a nerve fiber between two Nodes of Ranvier. The neurolemma or primitive sheath is not interrupted at the nodes, but passes over them as a continuous membrane.

No elevation of the disc borders. Disruption of the normal radial NFL arrangement with grayish opacity accentuating nerve fiber layer bundles. Normal temporal disc margin. Subtle grayish halo with temporal gap (best seen with indirect ophthalmoscopy).

Warren Grill and J. Thomas Mortimer, may be observed in the adjacent image. Building upon this, a stimulus with two depolarizing prepulses, each of an amplitude slightly below the threshold current (at the time of delivery), should increase the radii of influence for nearby nerve fiber inactivation and distant nerve fiber excitation. Typically, nerve fibers of a larger diameter may be activated by single-pulse stimuli of a lower intensity, and thus may be recruited more readily. However, DPPs have demonstrated the additional capability to invert this recruitment order.

Patients with retinitis pigmentosa have abnormal thinning of the RNFL which correlates with the severity of the disease.Walia S, Fishman GA, Edward DP, Lindeman M. Retinal nerve fiber layer defects in RP patients. Invest Ophthalmol Vis Sci. 2007 Oct;48(10):4748-52.

However, also birefringent properties of the cornea and the retinal nerve fiber layer are sources of birefringence. Corneal birefringence varies widely from one individual to another, as well as from one location to another for the same individual, thus can confound measurements.

Studies involving the dissection of cadavers have uncovered a 43% decrease in the cell body size of neurons found in the premotor cortex compared to those of younger adults. New studies have recently verified this finding in living subjects using high resolution magnetic resonance imaging (MRI). Recent evidence suggests that aging is also related to the loss of myelinated nerve fiber length and the mass of white matter, with individuals losing approximately 45% of total nerve fiber length as they age. These changes that develop through the aging process affect the connectivity of the cortex within itself as well as its connectivity to the rest of the central nervous system.

Research utilizing a visual stimulus and AOSLO eye tracking have yielded data on how the retina tracks movement at the microscopic level. The high degree of specificity and the ability to focus the laser on different levels of the eyes with AOSLO has additionally allowed for real time tracking of blood flow in the eye. By injecting fluorescin into macaques before scanning, fluorescence adaptive optics scanning laser ophthalmoscopy (FAOSLO) can be utilized to image individual capillaries in the nerve fiber layer and determine the thickness of the nerve fiber layer itself. Vessel pattern and diameter for these capillaries have been measured throughout the regions scanned by FAOSLO.

Epiretinal membrane is typically diagnosed by appearance with optical coherence tomography (OCT) of the macula. Features include a thickening of the nerve fiber layer, a serrated appearance to the surface of the retina just beneath a thickened layer of glial tissue at the retinal-vitreous interface.

Cerebral cortex. (Poirier.) To the left, the groups of cells; to the right, the systems of fibers. Quite to the left of the figure a sensory nerve fiber is shown. Cell body layers are labeled on the left, and fiber layers are labeled on the right.

Tactile corpuscles are encapsulated myelinated nerve endings, which consist of flattened supportive cells arranged as horizontal lamellae surrounded by a connective tissue capsule. The corpuscle is 30–140 μm in length and 40–60 μm in diameter. A single nerve fiber meanders between the lamellae and throughout the corpuscle.

The eye in mammals has an extensive laminar organization. There are three main layers – the outer fibrous tunic, the middle uvea, and the inner retina. These layers have sublayers with the retina having ten ranging from the outer choroid to the inner vitreous humor and including the retinal nerve fiber layer.

The glomerulus in the granular layer of the cerebellum The cerebellar glomerulus is a small, intertwined mass of nerve fiber terminals in the granular layer of the cerebellar cortex. It consists of post-synaptic granule cell dendrites and pre-synaptic Golgi cell axon terminals surrounding the pre- synaptic terminals of mossy fibers.

Because long periods of contact lens wear are correlated with extended hypoxia, the resurgence of cellular growth and epithelial metabolism following contact lens removal (and hence, improved oxygen circulation) leads to an initial, increased resurgence of microcysts containing cellular debris. Over time, however, microcysts will disappear if contact lenses are not worn. Corneal sensitivity has been found to be significantly diminished following long-term contact lens wear. However, this difference in sensitivity is not correlated with a change in the number of nerve fiber bundles in the subbasal plexus of the cornea, suggesting that diminished corneal sensitivity following extended periods of contact lens wear is not caused by a reduction in nerve fiber bundles but possibly a change in functionality.

Sympathetic nerve fiber impulses stimulate the release of adrenal medullary hormones. In this way the sympathetic division of the autonomic nervous system and the medullary secretions function together. The major center of neuroendocrine integration in the body is found in the hypothalamus and the pituitary gland. Here hypothalamic neurosecretory cells release factors to the blood.

Skin used by the single receptor ending of a temperature-sensitive nerve fiber is small. There are 20 cold points per square centimeter in the lips, 4 in the finger, and less than 1 cold point per square centimeter in trunk areas. There are 5 times as many cold sensitive points as warm sensitive points.

In 1951, Sunderland expanded Seddon's classification to five degrees of peripheral nerve injury: ;First-degree (Class I): Seddon's neurapraxia and first-degree are the same. ;Second-degree (Class II): Seddon's axonotmesis and second-degree are the same. ;Third-degree (Class III): Third-degree is included within Seddon's Neurotmesis. Sunderland's third-degree is a nerve fiber interruption.

The cause is generally either paraneoplastic syndrome or idiopathic. In idiopathic AAG, the body's own immune system targets a receptor in the autonomic ganglia, which is part of a peripheral nerve fiber. If the AAG is paraneoplastic, they have a form of cancer, and their immune system has produced paraneoplastic antibodies in response to the cancer.

A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. Afferent in this case means bringing information from the body's periphery toward the brain. They function as cutaneous nociceptors and are essentially used by vertebrates to detect noxious stimuli that often result in pain.

Rat microglia grown in tissue culture in green, along with nerve fiber processes shown in red. Microglia in rat cerebellar molecular layer in red, stained with antibody to IBA1/AIF1. Bergmann glia processes are shown in green, DNA in blue. Microglial cells are extremely plastic, and undergo a variety of structural changes based on location and system needs.

Each ommatidium feeds into a single nerve fiber. Furthermore, the nerves are large and relatively accessible. This made it possible for electrophysiologists to record the nervous response to light stimulation easily, and to observe visual phenomena such as lateral inhibition working at the cellular level. More recently, behavioral experiments have investigated the functions of visual perception in Limulus.

Pagel: Biographical Dictionary excellent doctors of the nineteenth century. Berlin, Vienna, 1901, col 325-326. In the fields of anatomy and histology, he is known for studies involving the finer structure of the eye (microscopic investigations of the conjunctiva, cornea and vitreous). He also made contributions involving research of peripheral nerve fiber terminations in vertebrates (e.g.

There is much debate about the true cause and mechanism of the sneezing fits brought about by the photic sneeze reflex. Sneezing occurs in response to irritation in the nasal cavity, which results in an afferent nerve fiber signal propagating through the ophthalmic and maxillary branches of the trigeminal nerve to the trigeminal nerve nuclei in the brainstem. The signal is interpreted in the trigeminal nerve nuclei, and an efferent nerve fiber signal goes to different parts of the body, such as mucous glands and the thoracic diaphragm, thus producing a sneeze. The most obvious difference between a normal sneeze and a photic sneeze is the stimulus: normal sneezes occur due to irritation in the nasal cavity, while the photic sneeze can result from a wide variety of stimuli.

Some patients suffering from copper deficiency have shown signs of vision and color loss. The vision is usually lost in the peripheral views of the eye. The bilateral vision loss is usually very gradual. An optical coherence tomography (OCT) shows some nerve fiber layer loss in most patients, suggesting the vision loss and color vision loss was secondary to optic neuropathy or neurodegeneration.

A muscle spindle, with γ motor and Ia sensory fibers A type Ia sensory fiber, or a primary afferent fiber is a type of afferent nerve fiber. It is the sensory fiber of a stretch receptor found in muscles called the muscle spindle, which constantly monitors how fast a muscle stretch changes. (In other words, it monitors the velocity of the stretch).

Some patients suffering from copper deficiency have shown signs of vision and color loss. The vision is usually lost in the peripheral views of the eye. The bilateral vision loss is usually very gradual. An optical coherence tomography (OCT) shows some nerve fiber layer loss in most patients, suggesting the vision loss and color vision loss was secondary to optic neuropathy or neurodegeneration.

In the resting state, the interior of the nerve fiber is negative to the exterior by approximately 70 to 90 millivolts.(from Jacob SW, francone CA: Structure and Function in Man, 5th ed. Philadelphia Saunders, 1992.) § RDH: Fabiola Wood During cortical reaction in fertilisationof sperm with secondary oocyte spike potential reaches above +30 mv (millivolts). This causes opening of voltage gated Ca2+ channels.

Joseph Erlanger (January 5, 1874 – December 5, 1965) was an American physiologist who is best known for his contributions to the field of neuroscience. Together with Herbert Spencer Gasser, he identified several varieties of nerve fiber and established the relationship between action potential velocity and fiber diameter. They were awarded the Nobel Prize in Physiology or Medicine in 1944 for these achievements.

With this research, the pair discovered that the velocity of action potentials was directly proportional to the diameter of the nerve fiber. The partnership ended in 1931, when Gasser accepted a position at Cornell University. In 1944, they won the Nobel Prize in Medicine or Physiology for these discoveries. He died of heart disease on December 5, 1965 at St. Louis, Missouri.

A fundus examination revealed a grade 1 bilateral optic-disc edema and choroidal folds (Figure 15). Figure 15: Preflight images of the right and left optic discs (upper). Postflight images of the ONH showing in more detail the extent of the edematous optic-disc margins and glutting of the superior and inferior nerve fiber layer axons OD and OS (arrows) (lower).

The retinal nerve fiber layer (RNFL) or nerve fiber layer, stratum opticum, is formed by the expansion of the fibers of the optic nerve; it is thickest near the optic disc, gradually diminishing toward the ora serrata. As the nerve fibers pass through the lamina cribrosa sclerae they lose their medullary sheaths and are continued onward through the choroid and retina as simple axis-cylinders. When they reach the internal surface of the retina they radiate from their point of entrance over this surface grouped in bundles, and in many places arranged in plexuses. Most of the fibers are centripetal, and are the direct continuations of the axis-cylinder processes of the cells of the ganglionic layer, but a few of them are centrifugal and ramify in the inner plexiform and inner nuclear layers, where they end in enlarged extremities.

The most distinctive feature of the genus are a pair of translucent leaf-like flaps on the snout, forward of the eyes and flanking the esca. Each flap has a central opaque nerve fiber running from the base to the tip. In some specimens, there is another, smaller pair of similar flaps placed above the main pair. Males and larvae have yet to be encountered.

Peripheral neuropathy may be classified according to the number and distribution of nerves affected (mononeuropathy, mononeuritis multiplex, or polyneuropathy), the type of nerve fiber predominantly affected (motor, sensory, autonomic), or the process affecting the nerves; e.g., inflammation (neuritis), compression (compression neuropathy), chemotherapy (chemotherapy-induced peripheral neuropathy). The affected nerves are found in an EMG / NCS test and the classification is applied upon completion of the exam.

Those with diseases or dysfunctions of their nerves may present with problems in any of the normal nerve functions. Symptoms vary depending on the types of nerve fiber involved. In terms of sensory function, symptoms commonly include loss of function ("negative") symptoms, including numbness, tremor, impairment of balance, and gait abnormality. Gain of function (positive) symptoms include tingling, pain, itching, crawling, and pins-and-needles.

Regardless of which kind of trigger initiates the damage, the axons themselves and the oligodendrocytes. are finally damaged by the T-cell attacks.Cause of nerve fiber damage in multiple sclerosis identified Often, the brain is able to compensate for some of this damage, due to an ability called neuroplasticity. MS symptoms develop as the cumulative result of multiple lesions in the brain and spinal cord.

An ophthalmoscopic view of the retina showing advanced signs of diabetic retinopathy including two pale cotton wool spots. Cotton wool spots are an abnormal finding on funduscopic exam of the retina of the eye. They appear as fluffy white patches on the retina. They are caused by damage to nerve fibers and are a result of accumulations of axoplasmic material within the nerve fiber layer.

At the neuromuscular junction, the nerve fiber is able to transmit a signal to the muscle fiber by releasing ACh (and other substances), causing muscle contraction. Muscles will contract or relax when they receive signals from the nervous system. The neuromuscular junction is the site of the signal exchange. The steps of this process in vertebrates occur as follows:(1) The action potential reaches the axon terminal.

Myelin incisures (also known as Schmidt-Lanterman clefts, Schmidt-Lanterman incisures, clefts of Schmidt-Lanterman, segments of Lanterman, medullary segments), are small pockets of cytoplasm left behind during the Schwann cell myelination process. They are histological evidence of the small amount of cytoplasm that remains in the inner layer of the myelin sheath created by Schwann cells wrapping tightly around an axon (nerve fiber).

Optic-disc edema will be graded based on the Frisén Scale as below: Stage 0 – Normal Optic-disc Blurring of nasal, superior and inferior poles in inverse proportion to disc diameter. Radial nerve fiber layer (NFL) without NFL tortuosity. Rare obscuration of a major blood vessel, usually on the upper pole. Stage 1 – Very early optic-disc edema Obscuration of the nasal border of the disc.

Group C nerve fibers are one of three classes of nerve fiber in the central nervous system (CNS) and peripheral nervous system (PNS). The C group fibers are unmyelinated and have a small diameter and low conduction velocity, whereas Groups A and B are myelinated. Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots (IV fiber). These fibers carry sensory information.

Sub-optimal compensation of corneal birefringence is currently being addressed by the manufacturer with hardware and software modifications. The GDx scanning laser measures the thickness of the retinal nerve fiber layer, which is the very first part of your eye that is damaged by glaucoma. Before we go any further, let us describe the basic GDx instrument. This instrument use a GaAIAs diode laser as a source of light.

Use of ultrasound in phacoemulsification can cause effects such as corneal edema, and macular edema after surgery. However, in some cases, use of ultrasound energy does not generate macular edema. The cause of macular edema in phacoemulsification is intraocular pressure fluctuation during surgery. Intraocular fluctuation can create micro bubbles and generate micro emboli in macular vessels that can cause micro ischemia in the retinal nerve fiber layer (RNFL).

Neurilemma (also known as neurolemma, sheath of Schwann, or Schwann's sheath) is the outermost nucleated cytoplasmic layer of Schwann cells (also called neurilemmocytes) that surrounds the axon of the neuron. It forms the outermost layer of the nerve fiber in the peripheral nervous system. The neurilemma is underlain by the myelin sheath (also known as the medullary sheath). In the central nervous system, axons are myelinated by oligodendrocytes, thus lack neurilemma.

Radial neuropathy is not necessarily permanent, though there could be partial loss of movement or sensation. Complications include deformity of the hand in some individuals. If the injury is axonal (the underlying nerve fiber itself is damaged), recovery may take months or years and full recovery may never occur. EMG and nerve conduction studies are typically performed to diagnose the extent and distribution of the damage, and to help with prognosis for recovery.

Intraocular pressure laws follow fundamentally from physics. Any kinds of intraocular surgery should be done by considering the intraocular pressure fluctuation. Sudden increase of intraocular pressure can lead to intraocular micro barotrauma and cause ischemic effects and mechanical stress to retinal nerve fiber layer. Sudden intraocular pressure drop can lead to intraocular decompression that generates micro bubbles that potentially cause multiple micro emboli and leading to hypoxia, ischemia and retinal micro structure damage.

Hair plexus. A hair plexus or root hair plexus is a special group of nerve fiber endings and serves as a very sensitive mechanoreceptor for touch sensation. Each hair plexus forms a network around a hair follicle and is a receptor, which means it sends and receives nerve impulses to and from the brain when the hair moves. Endings of sensory nerve fibers which form a plexus around a hair follicle in hairy skin.

"eye, human."Encyclopædia Britannica. 2008. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD It is the only part of the CNS that can be imaged non-invasively in the living organism. The retina nerve fiber layer (RNFL) is thinner than normal in MS patients The procedure by which the MS underlying condition attacks the retina is currently unknown, but seems mediated by human leukocyte antigen-DR positive cells with the phenotype of microglia.

Any physical deformation of the corpuscle will cause sodium ions to enter it, creating an action potential in the corpuscle's nerve fiber. Since they are rapidly adapting or phasic, the action potentials generated quickly decrease and eventually cease (this is the reason one stops "feeling" one's clothes). If the stimulus is removed, the corpuscle regains its shape and while doing so (i.e.: while physically reforming) causes another volley of action potentials to be generated.

The severity of brachial plexus injury is determined by the type of nerve damage. There are several different classification systems for grading the severity of nerve and brachial plexus injuries. Most systems attempt to correlate the degree of injury with symptoms, pathology and prognosis. Seddon's classification, devised in 1943, continues to be used, and is based on three main types of nerve fiber injury, and whether there is continuity of the nerve.

Radial neuropathy is not necessarily permanent. The majority of radial neuropathies due to an acute compressive event (Saturday night palsy) do recover without intervention. If the injury is demyelinating (meaning only the myelin sheath surrounding the nerve is damaged), then full recovery typically occurs within 2–4 weeks. If the injury is axonal (meaning the underlying nerve fiber itself is damaged) then full recovery may take months or years, or may never occur.

Exocytosis of a vesicle. 8. Recaptured neurotransmitter. Axon terminals (also called synaptic boutons, terminal boutons, or end-feet) are distal terminations of the telodendria (branches) of an axon. An axon, also called a nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses called action potentials away from the neuron's cell body, or soma, in order to transmit those impulses to other neurons, muscle cells or glands.

Headaches often result from traction to or irritation of the meninges and blood vessels. The pain receptors may be stimulated by head trauma or tumors and cause headaches. Blood vessel spasms, dilated blood vessels, inflammation or infection of meninges and muscular tension can also stimulate pain receptors. Once stimulated, a nociceptor sends a message up the length of the nerve fiber to the nerve cells in the brain, signaling that a part of the body hurts.

To investigate the mechanisms of this sensitization, Wasner et al., 2004, performed A fiber conduction blockade of the superficial radial nerve in another group of subjects. This ended up reducing the menthol-induced sensation of cold and hyperalgesia because blocking A fiber conduction resulted in inhibition of a class of group C nerve fiber nociceptors needed to transduce the sensation of pain. They concluded menthol sensitizes cold-sensitive peripheral C nociceptors and activates cold-specific A delta fibers.

Group A nerve fibers are one of the three classes of nerve fiber as generally classified by Erlanger and Gasser. The other two classes are the group B nerve fibers, and the group C nerve fibers. Group A are heavily myelinated, group B are moderately myelinated, and group C are unmyelinated. The other classification is a sensory grouping that uses the terms type Ia and type Ib, type II, type III, and type IV, sensory fibers.

Patients with optic disc drusen should be monitored periodically via ophthalmoscopy, Snellen acuity, contrast sensitivity, color vision, intraocular pressure and threshold visual fields. For those with visual field defects optical coherence tomography has been recommended for follow up of nerve fiber layer thickness. Associated conditions such as angioid streaks and retinitis pigmentosa should be screened for. Both the severity of optic disc drusen and the degree of intraocular pressure elevation have been associated with visual field loss.

This typically evolves to very severe optic atrophy and a permanent decrease of visual acuity. Both eyes become affected either simultaneously (25% of cases) or sequentially (75% of cases) with a median inter-eye delay of 8 weeks. Rarely only one eye may be affected. In the acute stage, lasting a few weeks, the affected eye demonstrates an oedematous appearance of the nerve fiber layer especially in the arcuate bundles and enlarged or telangiectatic and tortuous peripapillary vessels (microangiopathy).

Most individual axons are microscopic in diameter (typically about one micrometer (µm) across). The largest mammalian axons can reach a diameter of up to 20 µm. The squid giant axon, which is specialized to conduct signals very rapidly, is close to 1 millimetre in diameter, the size of a small pencil lead. The numbers of axonal telodendria (the branching structures at the end of the axon) can also differ from one nerve fiber to the next.

Corneal sensitivity is significantly diminished after extended contact lens wear (five or more years). However, this difference in sensitivity is not correlated with a change in the number of nerve fiber bundles in the subbasal plexus of the cornea. Long-term use of PMMA or thick hydrogel contact lenses have been found to cause increased eye irritability, photophobia, blurred vision, and persistent haloes. Long-term use of rigid gas permeable contact lenses has been associated with slower myopic progression.

Vision loss in dominant optic atrophy is due to optic nerve fiber loss from mitochondria dysfunction. Dominant optic atrophy is associated with mutation of the OPA1 gene found on chromosome 3, region q28-qter. Also, 5 other chromosomal genes are described as causing optic atrophy: OPA2 (x-linked), OPA3 (dominant), OPA4 (dominant), OPA5 (dominant) and OPA6 (recessive) (see OMIM 165500). The OPA1 gene codes for a dynamin-related GTPase protein targeted to the mitochondrial inner membrane.

Possible biomedical-oriented applications of this technique are related to the study of the myelin and myelopathies. Myelin is a highly ordered structure, in which many lipid- enriched, densely compacted phospholipid bilayers are spirally rolled up around the cylindrical axons. The linear acyl chains of the phospholipid molecules present a perpendicular orientation with respect to the myelin surface. Therefore, in a myelinated nerve fiber, a large number of molecular bonds are ordered around a radial axis of symmetry.

Nerve compression in neurapraxia 300px Neurapraxia is the least severe form of nerve injury, with complete recovery. In this case, the axon remains intact, but there is myelin damage causing an interruption in conduction of the impulse down the nerve fiber. Most commonly, this involves compression of the nerve or disruption to the blood supply (ischemia). There is a temporary loss of function which is reversible within hours to months of the injury (the average is 6–8 weeks).

The sucrose chamber (or gap) is the middle chamber that separates the two other chambers, or sections of the nerve fiber or cells. This chamber contains an isotonic sucrose solution of a high specific resistance. Specific resistance describes the ability of a material or solution to oppose electric current, so a sucrose solution of a high specific resistance is effective in electrically isolating the three chambers. The third chamber usually contains a KCl solution that mimics the intracellular solution.

It may therefore be useful to better simulate cochlear nucleus cell types to understand the true concepts for parallel processing created at the level of the cochlear nucleus. These concepts may be related to separating ENV and TFS but are unlikely realized like the Hilbert transform. A computational model of the peripheral auditory system may be used to simulate auditory-nerve fiber responses to complex sounds such as speech, and quantify the transmission (i.e., internal representation) of ENVn and TFSn cues.

However the thickness of the RNFL also decreases with age and not visual acuity.Oishi A, Otani A, Sasahara M, Kurimoto M, Nakamura H, Kojima H, Yoshimura N. Retinal nerve fiber layer thickness in patients with retinitis pigmentosa. Eye. 2008 Mar 14, online advance publication. The sparing of this layer is important in the treatment of the disease as it is the basis for connecting retinal prostheses to the optic nerve, or implanting stem cells that could regenerate the lost photoreceptors.

Regions of the cerebral cortex associated with pain. Wilhelm Erb's (1874) "intensive" theory, that a pain signal can be generated by intense enough stimulation of any sensory receptor, has been soundly disproved. Some sensory fibers do not differentiate between noxious and non-noxious stimuli, while others, nociceptors, respond only to noxious, high intensity stimuli. At the peripheral end of the nociceptor, noxious stimuli generate currents that, above a given threshold, send signals along the nerve fiber to the spinal cord.

Many of the myelin-recognizing T cells belong to a terminally differentiated subset called co-stimulation-independent effector- memory T cells. Recently other type of immune cells, B Cells, have been also implicated in the pathogenesis of MS and in the degeneration of the axons.Cause of nerve fiber damage in multiple sclerosis identified The axons themselves can also be damaged by the attacks. Often, the brain is able to compensate for some of this damage, due to an ability called neuroplasticity.

Nerve injury is injury to nervous tissue. There is no single classification system that can describe all the many variations of nerve injury. In 1941, Seddon introduced a classification of nerve injuries based on three main types of nerve fiber injury and whether there is continuity of the nerve. Usually, however, (peripheral) nerve injury is classified in five stages, based on the extent of damage to both the nerve and the surrounding connective tissue, since supporting glial cells may be involved.

Epiretinal implants are placed on top of the retinal surface, above the nerve fiber layer, directly stimulating ganglion cells and bypassing all other retinal layers. Array of electrodes is stabilized on the retina using micro tacks which penetrate into the sclera. Typically, external video camera onto eyeglasses acquires images and transmits processed video information to the stimulating electrodes via wireless telemetry. An external transmitter is also required to provide power to the implant via radio-frequency induction coils or infrared lasers.

One study showed nerve fiber impairments in which the shape and form of cortex and white matter tissue was altered. This was shown postnatally comparing KO mice and controls, where both cell number and cortical thickness was decreased in KO mice. Using a cell staining methodology for histological analysis, the study also showed shorter distances between adjacent neurons in KO mice, indicating abnormalities in cell alignment in the absence of normal Aspm. Another significant impact of mutated Aspm is seen in germline abnormalities within mouse models.

As for autopsies, the principal work of the neuropathologist is to help in the post-mortem diagnosis of various forms of dementia and other conditions that affect the central nervous system. Tissue samples are researched within the lab for diagnosis as well as forensic investigations. Biopsies can also consist of the skin. Epidermal nerve fiber density testing (ENFD) is a more recently developed neuropathology test in which a punch skin biopsy is taken to identify small fiber neuropathies by analyzing the nerve fibers of the skin.

Single-unit smooth muscle, or visceral smooth muscle is a type of smooth muscle found in the uterus, gastro-intestinal tract, and the bladder. In SUVSM, a single smooth muscle cell in a bundle is innervated by an autonomic nerve fiber. An action potential can be propagated through neighbouring muscle cells due to the presence of many gap junctions between the cells. Due to this property, SUVSM bundles form a syncytium that contracts in a coordinated fashion (such as uterine muscles do during childbirth).

The endoneurium contains a liquid known as endoneurial fluid, which contains little protein. In the peripheral nervous system the endoneurial fluid is notionally equivalent to cerebro-spinal fluid in the central nervous system. Peripheral nerve injuries commonly release increased amounts of endoneurial fluid into surrounding tissues; these can be detected by magnetic resonance neurography, thereby assisting in locating injuries to peripheral nerves. The endoneurium runs longitudinally along the nerve fiber, but with discontinuities where septa pass inward from the innermost layer of the perineurium.

GP-51, a specific glycosaminoglycan, lines healthy bladders of felines, where it prevents bacterial adherence and protects the bladder from the toxic properties of urine. Cats with interstitial cystitis, or inflammation of the bladder, excrete lower amounts of GP-51 along with other glycosaminoglycans, leaving the lining of the bladder exposed. Substances from the urine contact sensory neurons in the bladder, causing pain and neurogenic bladder inflammation. The sensory neurons are composed of unmyelinated C-fibers (group C nerve fiber), and when stimulated cause pelvic pain.

Quantitative assessment of ICP can be made noninvasively in two different ways: by measuring changes in diameter of the optic nerve sheath with an appropriate technique (ultrasound or MRI), or by using ophthalmodynamometry to determine the pressure in the central retinal vein, which is normally slightly higher (1- 2mmHg) than ICP. Intracranial hypertension also induces changes at the cellular or axonal level such as the swelling of the fibers of the optic nerve that form the innermost layer of the retina (so-called nerve fiber layer – NFL). The information provided by the classic ophthalmoscopy is however only qualitative and may be inconclusive during early phases of intracranial hypertension since it usually takes between two and four hours from the onset of ICP elevation for a papilledema to develop. A patented method that utilizes optical coherence tomography to measure the thickness of the nerve fiber layer and infers ICP from it laid claims of being able to detect the IH-induced thickening of the retina shortly after the onset of IH, but there has been no data that would support the claims or clarify the relationship between the NFL thickness and levels of ICP.

The nervous system is the system of neurons, or nerve cells, that relay electrical signals through the brain and body. A nerve cell receives signals from other nerve cells through tree-branch-like extensions called dendrites and passes signals on through a long extension called an axon (or nerve fiber). Synapses are places where one cell's axon passes information to another cell's dendrite by sending chemicals called neurotransmitters across a small gap called a synaptic cleft. Synapses occur in various locations, including ganglia (singular: ganglion), which are masses of nerve cell bodies.

Anterograde degeneration in the nervous system, also known as Wallerian degeneration, is a process of deterioration down the axon of a nerve cell away from the cell body. This degeneration is the result of damage or injury to a nerve fiber, and it causes the affected fiber to appear “coagulated” or “curdled.” It was discovered by Ludwig Turck that anterograde degeneration can be used to trace axonal pathways in the nervous system. It was also found that the coagulated fragments produced by anterograde degeneration have a high affinity for impregnation by silver.

All of these sensations travel along the same general pathways towards the brain. One pathwaydorsal column-medial lemniscus pathwaybegins with sensation from the periphery being sent via afferent nerve fiber of the dorsal root ganglion (first order neuron) through the spinal cord to the dorsal column nuclei (second order neuron) in the brainstem. The second order neuron's projection decussates at the medulla through medial lemniscus to the third order neurons in the thalamus. The third order neuron's axon terminates at the primary somatosensory cortex of the parietal lobe.

In 2003, vigabatrin was shown by Frisén and Malmgren to cause irreversible diffuse atrophy of the retinal nerve fiber layer in a retrospective study of 25 patients. This has the most effect on the outer area (as opposed to the macular, or central area) of the retina. Visual field defects had been reported as early as 1997 by Tom Eke and others, in the UK. Some authors, including Comaish et al. believe that visual field loss and electrophysiological changes may be demonstrable in up to 50% of Vigabatrin users.

With regard to fiber diameter there are two main categories: A-fibers are large and conduct impulses at high or moderate speed (5–75 m/s). C-fibers are small and conduct impulses at low speed (around 1 m/s). In microneurography recordings, A- and C-fiber impulses differ in shape. Because fibers are mixed in most nerves, it is usually essential to record from an individual nerve fiber at a time to explore the properties of a functional system, although multi-unit recording has been very rewarding in studies of sympathetic efferent activity.

With autopsies, the principal work of the neuropathologist is to help in the post-mortem diagnosis of various conditions that affect the central nervous system. Biopsies can also consist of the skin. Epidermal nerve fiber density testing (ENFD) is a more recently developed neuropathology test in which a punch skin biopsy is taken to identify small fiber neuropathies by analyzing the nerve fibers of the skin. This test is becoming available in select labs as well as many universities; it replaces the traditional nerve biopsy test as less invasive.

"Implementation details of a computational model of the inner hair-cell/auditory nerve synapse". Journal of the Acoustical Society of America 87(4) 1813-1816. Based on the assumption that there are three reservoirs of transmitter substance within each hair cell, and the transmitters are released in proportion to the degree of displacement to the basilar membrane, the release is equated with the probability of a spike generated in the nerve fiber. This model replicates many of the nerve responses in the CASA systems such as rectification, compression, spontaneous firing, and adaptation.

The following layer contains the cell bodies of different cell types, and the last layer consists of neuropil. It is from the neuropil layer that the optic nerve projects in several small branches that eventually merge to form a single nerve fiber. Strombus has almost 100,000 photoreceptors, whereas some nudibranchs merely have five. Three distinct cell types have been described in the retinas of C. luhuanus, one of which is a photoreceptor, another which is a glial cell, and the last which may be a second type of photoreceptor.

Scanning laser polarimetry is the use of polarised light to measure the thickness of the retinal nerve fiber layer as part of a glaucoma workup. The GDx-VCC is one example. However a Dutch study found that while there is a correlation between standard automated perimetry and GDx VCC measurements in patients with glaucoma, suggesting that GDx VCC measurements relate well with functional loss in glaucoma, in healthy subjects, they found virtually no correlation between perimetry and GDx VCC measurements. This would cast doubt on its predictive value and suggests false positives.

The activating function is a mathematical formalism that is used to approximate the influence of an extracellular field on an axon or neurons. It was developed by Frank Rattay and is a useful tool to approximate the influence of functional electrical stimulation (FES) or neuromodulation techniques on target neurons. It points out locations of high hyperpolarization and depolarization caused by the electrical field acting upon the nerve fiber. As a rule of thumb, the activating function is proportional to the second-order spatial derivative of the extracellular potential along the axon.

The endoneurium (also called endoneurial channel, endoneurial sheath, endoneurial tube, or Henle's sheath) is a layer of delicate connective tissue around the myelin sheath of each myelinated nerve fiber in the peripheral nervous system. Its component cells are called endoneurial cells. The endoneuria with their enclosed nerve fibers are bundled into groups called nerve fascicles, each fascicle within its own protective sheath called a perineurium. In sufficiently large nerves multiple fascicles, each with its blood supply and fatty tissue, may be bundled within yet another sheath, the epineurium.

Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.

This case is interesting because the astronaut did not have disc edema or choroidal folds, but was documented to have nerve fiber layer (NFL) thickening, globe flattening, a hyperopic shift and subjective complaints of loss of near vision. The sixth case of visual changes of an ISS astronaut was reported after return to Earth from a 6-month mission. When he noticed that his far vision was clearer through his reading glasses. A fundus examination performed 3 weeks postflight documented a grade 1 nasal optic-disc edema in the right eye only.

This depolarization opens voltage-gated calcium channels to allow the further influx of calcium. This results in an increase in the calcium concentration, which triggers the exocytosis of neurotransmitter vesicles at ribbon synapses at the basolateral surface of the hair cell. The release of neurotransmitter at a ribbon synapse, in turn, generates an action potential in the connected auditory-nerve fiber. Hyperpolarization of the hair cell, which occurs when potassium leaves the cell, is also important, as it stops the influx of calcium and therefore stops the fusion of vesicles at the ribbon synapses.

Defined as stimulation at or above the sensory threshold and below the motor threshold, sensory-level stimulation is frequently achieved with a frequency in the 50-100 pps range, with short pulse and phase durations of 2-50 μs, and low intensities. Short pulses must be used to avoid producing tetanic muscular contractions - muscular movement is not desirable in sensory-level TENS. Amplitude is adjusted to achieve superficial cutaneous nerve fiber activation. The patient should perceive paresthesia beneath the electrodes and amplitude is adjusted according to patient feedback.

The Munsell value has long been used as a perceptually uniform lightness scale. A question of interest is the relationship between the Munsell value scale and the relative luminance. Aware of the Weber–Fechner law, Munsell remarked "Should we use a logarithmic curve or curve of squares?" Neither option turned out to be quite correct; scientists eventually converged on a roughly cube-root curve, consistent with the Stevens's power law for brightness perception, reflecting the fact that lightness is proportional to the number of nerve impulses per nerve fiber per unit time.

Each ganglion cell or optic nerve fiber bears a receptive field, increasing with intensifying light. In the largest field, the light has to be more intense at the periphery of the field than at the center, showing that some synaptic pathways are more preferred than others. The organization of ganglion cells' receptive fields, composed of inputs from many rods and cones, provides a way of detecting contrast, and is used for detecting objects' edges. Each receptive field is arranged into a central disk, the "center", and a concentric ring, the "surround", each region responding oppositely to light.

Action potential propagation in myelinated neurons is faster than in unmyelinated neurons because of saltatory conduction. Propagation of action potential along myelinated nerve fiber Saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials. The uninsulated nodes of Ranvier are the only places along the axon where ions are exchanged across the axon membrane, regenerating the action potential between regions of the axon that are insulated by myelin, unlike electrical conduction in a simple circuit.

The way in which rotation sensation is accomplished is that there are five distinct sensory fields located at the base of the haltere. These fields, which actually contain the majority of campaniform sensilla found on the exoskeleton of blowflies (more than 400 campaniform sensilla per haltere), are activated in response to strain created by movements at the haltere base in different directions (due to Coriolis forces acting on the end knobs). Campaniform sensilla are cap-shaped protrusions located on the surface of the exoskeleton (cuticle) of insects. Attached inside the cap is the tip of a dendritic projection (or sensory nerve fiber).

The microneurography technique allows the recording of impulse activity of individual nerve fibers with absolute resolution in attending human subjects. Hence the subject is able to cooperate in various kinds of tests while the exact and complete information carried by the individual nerve fiber is monitored and offered for analysis of correlations between neural activity and physical or mental events. On the other hand, the particular physical conditions involving a microelectrode freely floating in the tissue preclude brisk and large movements because the exact electrode position is easily jeopardized. The experiment is often time-consuming because the search procedure can be particularly demanding.

Wallerian degeneration is an active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (i.e. farther from the neuron's cell body) degenerates.Trauma and Wallerian Degeneration, University of California, San Francisco A related process of dying back or retrograde degeneration known as 'Wallerian-like degeneration' occurs in many neurodegenerative diseases, especially those where axonal transport is impaired such as ALS and Alzheimer's disease. Primary culture studies suggest that a failure to deliver sufficient quantities of the essential axonal protein NMNAT2 is a key initiating event.

The axons of neurons in the human peripheral nervous system can be classified based on their physical features and signal conduction properties. Axons were known to have different thicknesses (from 0.1 to 20 µm) and these differences were thought to relate to the speed at which an action potential could travel along the axon – its conductance velocity. Erlanger and Gasser proved this hypothesis, and identified several types of nerve fiber, establishing a relationship between the diameter of an axon and its nerve conduction velocity. They published their findings in 1941 giving the first classification of axons.

As the study of the cochlea should fundamentally be focused at the level of hair cells, it is important to note the anatomical and physiological differences between the hair cells of various species. In birds, for instance, instead of outer and inner hair cells, there are tall and short hair cells. There are several similarities of note in regard to this comparative data. For one, the tall hair cell is very similar in function to that of the inner hair cell, and the short hair cell, lacking afferent auditory-nerve fiber innervation, resembles the outer hair cell.

Ludwig Türck (1810-1868) Ludwig Türck (22 June 1810 – 25 February 1868) was an Austrian neurologist who was a native of Vienna. In 1836 he obtained his medical doctorate from the University of Vienna, where in 1864 he became a full professor. He is remembered for his pioneer investigations of the central nervous system, particularly his studies involving nerve fiber localization, direction and degeneration. The human brain and spinal cord by Edwin Clarke and Charles Donald O'Malley His name is lent to the "bundle of Türck", which are uncrossed fibers forming a small bundle in the pyramidal tract.

A neurolytic block is a form of nerve block involving the deliberate injury of a nerve by the application of chemicals (in which case the procedure is called "neurolysis") or physical agents such as freezing or heating ("neurotomy"). These interventions cause degeneration of the nerve's fibers and temporary interference with the transmission of pain signals. In these procedures, the thin protective layer around the nerve fiber (the basal lamina) is preserved so that as a damaged fiber regrows, it travels within its basal lamina tube and connects with the correct loose end; thus function may be restored.

Put together in modern neuroanatomical terms they mean that a nerve fiber from a fixed retinal location instructs its target neurons in the brain about the presence of a stimulus in the location in the eye's visual field that is imaged there. The orderly array of retinal locations is preserved in the passage from the retina to the brain, and provides what is aptly called a "retinotopic" mapping in the primary visual cortex. Thus in the first instance brain activity retains the relative spatial ordering of the objects and lays the foundations for a neural substrate of visual space. Unfortunately simplicity and transparency ends here.

Sommer made a number of other discoveries that have led to major advances in global health care and policies, including demonstrating that measurement of mid-arm-circumference (MUAC) is a simple and effective tool for conducting nutritional surveillance and identifying children and populations at high risk of dying from malnutrition; that the easily assessed appearance of the nerve fiber layer in the retina is an early, accurate predictor of glaucomatous optic nerve damage indicating the need to initiate glaucoma therapy; and that vaccination for smallpox as long as 6 days after infection can prevent the disease, an observation that forestalled mass vaccination of primary responders following 9/11.

In medicine, the colloquial term "touch" is usually replaced with "somatic senses" to better reflect the variety of mechanisms involved. Insensitivity to somatosensory stimuli, such as heat, cold, touch, and pain, are most commonly a result of a more general physical impairment associated with paralysis. Damage to the spinal cord or other major nerve fiber may lead to a termination of both afferent and efferent signals to varying areas of the body, causing both a loss of touch and a loss of motor coordination. Other types of somatosensory loss include hereditary sensory and autonomic neuropathy, which consists of ineffective afferent neurons with fully functioning efferent neurons; essentially, motor movement without somatosensation.

They discovered that nerves were found in many forms, each with their own potential for excitability. With this research, the pair discovered that the velocity of action potentials was directly proportional to the diameter of the nerve fiber and received a Nobel Prize for their work. Kenneth Cole joined Columbia University in 1937 and remained there until 1946 where he made pioneering advances modelling the electrical properties of nervous tissue. Bernstein's hypothesis about the action potential was confirmed by Cole and Howard Curtis, who showed that membrane conductance increases during an action potential. David E. Goldman worked with Cole and derived the Goldman equation in 1943 at Columbia University.

Denervation of skeletal muscle tissue secondary to poliovirus infection can lead to paralysis. In around 1 percent of infections, poliovirus spreads along certain nerve fiber pathways, preferentially replicating in and destroying motor neurons within the spinal cord, brain stem, or motor cortex. This leads to the development of paralytic poliomyelitis, the various forms of which (spinal, bulbar, and bulbospinal) vary only with the amount of neuronal damage and inflammation that occurs, and the region of the CNS affected. The destruction of neuronal cells produces lesions within the spinal ganglia; these may also occur in the reticular formation, vestibular nuclei, cerebellar vermis, and deep cerebellar nuclei.

Vestibular duct perilymph vibrations bend organ of Corti outer cells (4 lines) causing prestin to be released in cell tips. This causes the cells to be chemically elongated and shrunk (somatic motor), and hair bundles to shift which, in turn, electrically affects the basilar membrane’s movement (hair-bundle motor). These motors (outer hair cells) amplify the traveling wave amplitudes over 40-fold. The outer hair cells (OHC) are minimally innervated by spiral ganglion in slow (unmyelinated) reciprocal communicative bundles (30+ hairs per nerve fiber); this contrasts inner hair cells (IHC) that have only afferent innervation (30+ nerve fibers per one hair) but are heavily connected.

Since the nerve fiber layer has similar stimulation threshold to that of the retinal ganglion cells, axons passing under the epiretinal electrodes are stimulated, creating arcuate percepts, and thereby distorting the retinotopic map. So far, none of the epiretinal implants had light-sensitive pixels, and hence they rely on external camera for capturing the visual information. Therefore, unlike natural vision, eye movements do not shift the transmitted image on the retina, which creates a perception of the moving object when person with such an implant changes the direction of gaze. Therefore, patients with such implants are asked to not move their eyes, but rather scan the visual field with their head.

In terms of anatomy, an auditory nerve fiber is either bipolar or unipolar, with its distal projection being called the peripheral process, and its central projection being called the axon; these two projections are also known as the "peripheral axon" and the "central axon", respectively. The peripheral process is sometimes referred to as a dendrite, although that term is somewhat inaccurate. Unlike the typical dendrite, the peripheral process generates and conducts action potentials, which then "jump" across the cell body (or soma) and continue to propagate along the central axon. In this respect, auditory nerve fibers are somewhat unusual in that action potentials pass through the soma.

In 2004, a study looked at how Lewis rats' sensory vs motor nerve grafts affected the regeneration of a cut mixed nerve system (both motor and sensory nerves). It was noted that after 3 weeks, a mixed nerve defect had undergone substantial regeneration when paired with a motor nerve graft or a mixed nerve graft. In comparison, a sensory nerve graft was statistically less affective in regeneration, looking specifically at nerve fiber count, percent nerve, and nerve densities as the main three comparisons between the different grafts. This means that the best surgical practices in regenerating nerves regarding PMR is using a nerve graft that is either a motor or a combination nerve graft.

Within 4 days of the injury, the distal end of the portion of the nerve fiber proximal to the lesion sends out sprouts towards those tubes and these sprouts are attracted by growth factors produced by Schwann cells in the tubes. If a sprout reaches the tube, it grows into it and advances about 1 mm per day, eventually reaching and reinnervating the target tissue. If the sprouts cannot reach the tube, for instance because the gap is too wide or scar tissue has formed, surgery can help to guide the sprouts into the tubes. Regeneration is efficient in the PNS, with near complete recovery in case of lesions that occur close to the distal nerve terminal.

The thermal radiation above a given threshold causes an increase in the temperature of the nerve fiber, resulting in stimulation of the nerve and subsequent firing, with increased temperature resulting in increased firing rate. The sensitivity of the nerve fibers is estimated to be >0.001 °C. The pit organ will adapt to a repeated stimulus; if an adapted stimulus is removed, there will be a fluctuation in the opposite direction. For example, if a warm object is placed in front of the snake, the organ will increase in firing rate at first, but after a while will adapt to the warm object and the firing rate of the nerves in the pit organ will return to normal.

This lesion causes a complete or partial action potential conduction block over a segment of a nerve fiber and thus a reduction or loss of function in parts of the neural connection downstream from the lesion, leading to muscle weakness. Neurapraxia results in temporary damage to the myelin sheath but leaves the nerve intact and is an impermanent condition; thus, Wallerian degeneration does not occur in neurapraxia. In order for the condition to be considered neurapraxia, according to the Seddon classification system of peripheral nerve injury, there must be a complete and relatively rapid recovery of motor and sensory function once nerve conduction has been restored; otherwise, the injury would be classified as axonotmesis or neurotmesis. Thus, neurapraxia is the mildest classification of peripheral nerve injury.

A chemoreceptor, also known as chemosensor, is a specialized sensory receptor cell which transduces a chemical substance (endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis.

These tests include a sweat test and a tilt table test. Diagnosis of small fiber involvement in peripheral neuropathy may also involve a skin biopsy in which a 3 mm-thick section of skin is removed from the calf by a punch biopsy, and is used to measure the skin intraepidermal nerve fiber density (IENFD), the density of nerves in the outer layer of the skin. Reduced density of the small nerves in the epidermis supports a diagnosis of small-fiber peripheral neuropathy. Laboratory tests include blood tests for vitamin B-12 levels, a complete blood count, measurement of thyroid stimulating hormone levels, a comprehensive metabolic panel screening for diabetes and pre-diabetes, and a serum immunofixation test, which tests for antibodies in the blood.

In similar fashion, transient increases or decreases in firing rate from spontaneous levels signal the direction of linear accelerations of the head. The range of orientations of hair cells within the utricle and saccule combine to effectively gauge the linear forces acting on the head at any moment, in all three dimensions. Tilts of the head off the horizontal plane and translational movements of the head in any direction stimulate a distinct subset of hair cells in the saccular and utricular maculae, while simultaneously suppressing responses of other hair cells in these organs. Ultimately, variations in hair cell polarity within the otolith organs produce patterns of vestibular nerve fiber activity that, at a population level, unambiguously encode head position and the forces that influence it.

Vocal cord paresis, also known as recurrent laryngeal nerve paralysis or vocal fold paralysis, is an injury to one or both recurrent laryngeal nerves (RLNs), which control all muscles of the larynx except for the cricothyroid muscle. The RLN is important for speaking, breathing and swallowing. The primary larynx-related functions of the mainly efferent nerve fiber RLN, include the transmission of nerve signals to the muscles responsible for regulation of the vocal folds' position and tension to enable vocalization, as well as the transmission of sensory nerve signals from the mucous membrane of the larynx to the brain. A unilateral injury of the nerve typically results in hoarseness caused by a reduced mobility of one of the vocal folds.

The study used stimulus recordings to measure the action potential of the optic nerve fiber, and measured electrical movement of the neurons into the different eye specific layers of the retina. The recorded electrical activity from the neurons excited many ganglion cells. This study illustrated that the fired neurons created the connection between the retina and the geniculate nucleus. Overall, this study was a breakthrough in proving how light can move through the eye and be received by the brain so that images and the environment can be perceived rapidly. Baylor's study on “Multi-neuronal signals from the retina: acquisition and analysis” utilized a new method to observe the many electrical activities of all the neurons in a section of the retina of the eye.

Tarlov cysts, are type II innervated meningeal cysts, cerebrospinal-fluid- filled (CSF) sacs most frequently located in the spinal canal of the S1-to-S5 region of the spinal cord (much less often in the cervical, thoracic or lumbar spine), and can be distinguished from other meningeal cysts by their nerve- fiber-filled walls. Tarlov cysts are defined as cysts formed within the nerve- root sheath at the dorsal root ganglion. The etiology of these cysts is not well understood; some current theories explaining this phenomenon have not yet been tested or challenged but include increased pressure in CSF, filling of congenital cysts with one-way valves, inflammation in response to trauma and disease. They are named for American neurosurgeon Isadore Tarlov, who described them in 1938.

An axon (from Greek ἄξων áxōn, axis), or nerve fiber (or nerve fibre: see spelling differences), is a 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. The function of the axon is to transmit information to different neurons, muscles, and glands. In certain sensory neurons (pseudounipolar neurons), such as those for touch and warmth, the axons are called afferent nerve fibers and the electrical impulse travels along these from the periphery to the cell body, and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction has caused many inherited and acquired neurological disorders which can affect both the peripheral and central neurons.

Common causes of scotomata include demyelinating disease such as multiple sclerosis (retrobulbar neuritis), damage to nerve fiber layer in the retina (seen as cotton wool spots"The role of axoplasmic transport in the pathogenesis of retinal cotton-wool spots", D. McLeod, J. Marshall, E. M. Kohner, and A. C. Bird, Br J Ophthalmol (1977), 61(3), pages 177–191.) due to hypertension, toxic substances such as methyl alcohol, ethambutol and quinine, nutritional deficiencies, vascular blockages either in the retina or in the optic nerve, stroke or other brain injury, and macular degeneration, often associated with aging. Scintillating scotoma is a common visual aura in migraine."Possible Roles of Vertebrate Neuroglia in Potassium Dynamics, Spreading depression, and migraine", Gardner-Medwin, J. Exp. Biol. (1981), 95, pages 111-127 (Figure 4).

The MBL's contributions to neuroscience and sensory physiology are significant, fostered today by more than 65 visiting investigators and resident researchers in these fields, as well as five graduate- and post-graduate level Advanced Research Training courses. The MBL has been a magnet for the discipline since L.W. Williams in 1910 discovered, and John Zachary Young in 1936 rediscovered, the squid giant axon, a nerve fiber that is 20 times larger in diameter than the largest human axon. Young brought this locally abundant, ideal experimental system to the attention of his MBL colleague KS Cole, who in 1938 used it to record the resistance changes underlying the action potential, which provided evidence that ions flowing across the axonal membrane generate this electrical impulse. In 1938, Alan Lloyd Hodgkin came to the MBL to learn about the squid giant axon from Cole.

Vision loss usually starts off centrally in one eye and may lead to complete loss of vision after a period of time. The possible cognitive dysfunction is also rare in tumefactive cases. MS patients may show signs of cognitive impairment where there is a reduction in the speed of information processing, a weaker short-term memory and a difficulty in learning new concepts. This cognitive impairment is associated with the loss of brain tissue, known as brain atrophy which is a result of the demyelination process in MS. About fatigue: most MS patients experience fatigue and this could be a direct result of the disease, depression or sleep disturbances due to MS. It is not clearly understood how MS results in physical fatigue but it is known that the repetitive usage of the same neural pathways results in nerve fiber fatigue that could cause neurological symptoms.

There are two types: autonomic reflex arc (affecting inner organs) and somatic reflex arc (affecting muscles). Autonomic reflexes sometimes involve the spinal cord and some somatic reflexes are mediated more by the brain than the spinal cord. During a somatic reflex, nerve signals travel along the following pathway: # Somatic receptors in the skin, muscles and tendons # Afferent nerve fibers carry signals from the somatic receptors to the posterior horn of the spinal cord or to the brainstem # An integrating center, the point at which the neurons that compose the gray matter of the spinal cord or brainstem synapse # Efferent nerve fibers carry motor nerve signals from the anterior horn to the muscles # Effector muscle innervated by the efferent nerve fiber carries out the response. A reflex arc, then, is the pathway followed by nerves which (a.) carry sensory information from the receptor to the spinal cord, and then (b.) carry the response generated by the spinal cord to effector organs during a reflex action.