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Group B Nerve Fibres
Group B nerve fibers are one of the three classes of nerve fiber as generally classified by Erlanger and Gasser. They are moderately myelinated, which means less myelinated than group A nerve fibers, and more myelinated than group C nerve fibers. They have a medium conduction velocity of 3 to 14 m/s. They are usually general visceral afferent fibers and preganglionic nerve fibers of the autonomic nervous system The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo .... They are used in Bainbridge reflex as afferents. References Neurohistology {{neuroanatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axon
An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, in Vertebrate, vertebrates, that typically conducts electrical impulses known as action potentials away from the Soma (biology), 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 peripheral nervous system, periphery to the cell body and from the cell body to the spinal cord along another branch of the same axon. Axon dysfunction can be the cause of many inherited and acquired neurological disorders that affect both the Peripheral nervous system, peripheral and Central nervous system, central ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joseph Erlanger
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. Biography Erlanger was born on January 5, 1874, in San Francisco, California. His family was Jewish and his parents both immigrated from the Kingdom of Württemberg, Germany and met in California during the Gold Rush. Joseph was the sixth of seven children born to the couple. He completed his Bachelor of Science in Chemistry from the University of California, Berkeley in 1895. He then completed his M.D. in 1899 from the Johns Hopkins School of Medicine in Baltimore, Maryland, where he finished second in his class. Upon graduating, Erlanger interned at Johns Hopkins H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbert Spencer Gasser
Herbert Spencer Gasser (July 5, 1888 – May 11, 1963) was an American physiologist, and recipient of the Nobel Prize for Physiology or Medicine in 1944 for his work with action potentials in nerve fibers while on the faculty of Washington University in St. Louis, awarded jointly with Joseph Erlanger. Education Gasser was born in Platteville, Wisconsin, to Herman Gasser and Jane Elisabeth Griswold Gasser. His father was a physician from Dornbirn in the Austrian province of Vorarlberg; his mother was of New England Yankee and German Russian ancestry. Biography Gasser attended State Normal School in Platteville, then entered the University of Wisconsin in 1907. Finishing his undergraduate studies in zoology in only two years, he enrolled in the university's medical school in 1909, studying physiology under Joseph Erlanger, and pharmacology under Arthur S. Loevenhart. While still a student, he was named an instructor in pharmacology (1911). Since UW only provided preclinical medi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myelin
Myelin Sheath ( ) is a lipid-rich material that in most vertebrates surrounds the axons of neurons to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. The myelinated axon can be likened to an electrical wire (the axon) with insulating material (myelin) around it. However, unlike the plastic covering on an electrical wire, myelin does not form a single long sheath over the entire length of the axon. Myelin ensheaths part of an axon known as an internodal segment, in multiple myelin layers of a tightly regulated internodal length. The ensheathed segments are separated at regular short unmyelinated intervals, called nodes of Ranvier. Each node of Ranvier is around one micrometre long. Nodes of Ranvier enable a much faster rate of conduction known as saltatory conduction where the action potential recharges at each node to jump over to the next node, and so on till it reaches the axon terminal. At the terminal the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group A Nerve Fiber
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. Types There are four subdivisions of group A nerve fibers: alpha (α) Aα; beta (β) Aβ; , gamma (γ) Aγ, and delta (δ) Aδ. These subdivisions have different amounts of myelination and axon thickness and therefore transmit signals at different speeds. Larger diameter axons and more myelin insulation lead to faster signal propagation. Group A nerves are found in both motor and sensory pathways. Different sensory receptors are innervated by different types of nerve fibers. Proprioceptors are innervated by type Ia, Ib and I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group C Nerve Fiber
Group C nerve fibers are one of three classes of nerve fiber in the central nervous system (CNS) and peripheral nervous system (PNS). The Group C 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. Damage or injury to nerve fibers causes neuropathic pain. Capsaicin activates C fibre vanilloid receptors, providing the burning sensation associated with chili peppers. Structure and anatomy Location 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. Structure C fibers are unmyelinated unlike most other fibers in the nervous system. This lack of myelination is the cause of their slow conduction ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metre Per Second
The metre per second is the unit of both speed (a scalar quantity) and velocity (a vector quantity, which has direction and magnitude) in the International System of Units (SI), equal to the speed of a body covering a distance of one metre in a time of one second. As the base unit for speed in the SI, it is commonly used in physics, mechanics, and engineering contexts. It represents both scalar speed and vector velocity, depending on context. According to the definition of metre, is exactly \frac of the speed of light. The SI unit symbols are m/s, m·s−1, m s−1, or . Conversions is equivalent to: : = 3.6 km/h (exactly) : ≈ 3.2808 feet per second (approximately) : ≈ 2.2369 miles per hour (approximately) : ≈ 1.9438 knots (approximately) 1 foot per second = (exactly) 1 mile per hour = (exactly) 1 km/h = (exactly) History and Standardization The metre per second became the official SI derived unit for both speed and velocity with the establishment of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Visceral Afferent Fibers
The general visceral afferent (GVA) fibers conduct sensory impulses (usually pain or reflex sensations) from the internal organs, glands, and blood vessels to the central nervous system. They are considered to be part of the visceral nervous system, which is closely related to the autonomic nervous system, but 'visceral nervous system' and 'autonomic nervous system' are not direct synonyms and care should be taken when using these terms. Unlike the efferent fibers of the autonomic nervous system, the afferent fibers are not classified as either sympathetic or parasympathetic. GVA fibers create referred pain by activating general somatic afferent fibers where the two meet in the posterior grey column. The cranial nerves that contain GVA fibers include the glossopharyngeal nerve (CN IX) and the vagus nerve (CN X). Generally, they are insensitive to cutting, crushing or burning; however, excessive tension in smooth muscle and some pathological conditions produce visceral pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Preganglionic Nerve Fibers
In the autonomic nervous system, nerve fibers from the central nervous system to the ganglion are known as preganglionic nerve fibers. All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic (that is, these fibers use acetylcholine as their neurotransmitter) and they are myelinated. Sympathetic preganglionic fibers tend to be shorter than parasympathetic preganglionic fibers because sympathetic ganglia are often closer to the spinal cord than are the parasympathetic ganglia. Another major difference between the two ANS (autonomic nervous systems) is divergence. Whereas in the parasympathetic division there is a divergence factor of roughly 1:4, in the sympathetic division there can be a divergence of up to 1:20. This is due to the number of synapses formed by the preganglionic fibers with ganglionic neurons. See also * Nerve fiber * Grey column * Terminal cisterna * Rexed lamina * Postganglionic nerve fib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autonomic Nervous System
The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its Myocardial contractility, force of contraction, digestion, respiratory rate, pupillary dilation, pupillary response, Micturition, urination, and Animal sexual behaviour, sexual arousal. The fight-or-flight response, also known as the acute stress response, is set into action by the autonomic nervous system. The autonomic nervous system is regulated by integrated reflexes through the brainstem to the spinal cord and organ (anatomy), organs. Autonomic functions include control of respiration, heart rate, cardiac regulation (the cardiac control center), vasomotor activity (the vasomotor center), and certain reflex, reflex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
