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61-589: Jeryl Lynn are strains of mumps virus used in the Mumpsvax mumps vaccine made by Merck . The strains are named after Jeryl Lynn Hilleman . In 1963, Jeryl's father, Maurice Hilleman , was leading efforts to produce a mumps vaccine for Merck. He cultured the mumps virus from her throat, and in 1967 a vaccine was produced which is now widely used. The Jeryl Lynn strains used in the manufacture of Mumpsvax later turned out to contain two distinguishable viral substrains, JL1 and JL2 . Further research showed that

122-457: A basophilic ("base-loving") dye. These structures consist of rough endoplasmic reticulum and associated ribosomal RNA . Named after German psychiatrist and neuropathologist Franz Nissl (1860–1919), they are involved in protein synthesis and their prominence can be explained by the fact that nerve cells are very metabolically active. Basophilic dyes such as aniline or (weakly) hematoxylin highlight negatively charged components, and so bind to

183-426: A bit less than 1/10 of a volt at baseline. This voltage has two functions: first, it provides a power source for an assortment of voltage-dependent protein machinery that is embedded in the membrane; second, it provides a basis for electrical signal transmission between different parts of the membrane. Numerous microscopic clumps called Nissl bodies (or Nissl substance) are seen when nerve cell bodies are stained with

244-544: A decrease in firing rate), or modulatory (causing long-lasting effects not directly related to firing rate). The two most common (90%+) neurotransmitters in the brain, glutamate and GABA , have largely consistent actions. Glutamate acts on several types of receptors and has effects that are excitatory at ionotropic receptors and a modulatory effect at metabotropic receptors . Similarly, GABA acts on several types of receptors, but all of them have inhibitory effects (in adult animals, at least). Because of this consistency, it

305-406: A dendrite to another dendrite. The signaling process is partly electrical and partly chemical. Neurons are electrically excitable, due to the maintenance of voltage gradients across their membranes . If the voltage changes by a large enough amount over a short interval, the neuron generates an all-or-nothing electrochemical pulse called an action potential . This potential travels rapidly along

366-499: A majority of the population they decrease complications at the population level. Effectiveness when 90% of a population is vaccinated is estimated at 85%. Two doses are required for long term prevention. The initial dose is recommended between 12 and 18 months of age. The second dose is then typically given between two years and six years of age. Usage after exposure in those not already immune may be useful. Side effects are generally mild. It may cause mild pain and swelling at

427-748: A neuron leading to electrical activity, including pressure , stretch, chemical transmitters, and changes in the electric potential across the cell membrane. Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type. Thin neurons and axons require less metabolic expense to produce and carry action potentials, but thicker axons convey impulses more rapidly. To minimize metabolic expense while maintaining rapid conduction, many neurons have insulating sheaths of myelin around their axons. The sheaths are formed by glial cells: oligodendrocytes in

488-465: A neuron responds at all, then it must respond completely. Greater intensity of stimulation, like brighter image/louder sound, does not produce a stronger signal but can increase firing frequency. Receptors respond in different ways to stimuli. Slowly adapting or tonic receptors respond to a steady stimulus and produce a steady rate of firing. Tonic receptors most often respond to increased stimulus intensity by increasing their firing frequency, usually as

549-460: A neurotransmitter that binds to chemical receptors . The effect on the postsynaptic neuron is determined by the type of receptor that is activated, not by the presynaptic neuron or by the neurotransmitter. A neurotransmitter can be thought of as a key, and a receptor as a lock: the same neurotransmitter can activate multiple types of receptors. Receptors can be classified broadly as excitatory (causing an increase in firing rate), inhibitory (causing

610-465: A power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where greater intensity of a specific frequency (color) requires more photons, as the photons can not become "stronger" for a specific frequency. Other receptor types include quickly adapting or phasic receptors, where firing decreases or stops with a steady stimulus; examples include skin which, when touched causes neurons to fire, but if

671-496: A result, during World War II (1939-1945), the United States government targeted mumps for scientific research. The first experimental mumps vaccine was licensed in 1948; developed from inactivated virus, it only had short-term effectiveness. Improved vaccines became commercially available in the 1960s. In 1963, Maurice Hilleman of Merck & Co. took samples of the mumps virus from his daughter, who had contracted

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732-481: A two-dose immunization of MMR. While the initial vaccine in the 1940s was based on inactivated virus, subsequent preparations since the 1960s consist of live virus that has been weakened. Mumps vaccine is on the World Health Organization's List of Essential Medicines . There are a number of different types in use as of 2007. Mumpsvax is Merck 's brand of Jeryl Lynn strain vaccines. It

793-456: A universal classification of neurons that will apply to all neurons in the brain as well as across species. This is done by considering the three essential qualities of all neurons: electrophysiology, morphology, and the individual transcriptome of the cells. Besides being universal this classification has the advantage of being able to classify astrocytes as well. A method called patch-sequencing in which all three qualities can be measured at once

854-476: Is a component of Merck's three-virus MMR vaccine , and is the mumps vaccine standard in the United States. Mumpsvax is given by a subcutaneous injection of live virus reconstituted from freeze-dried ( lyophilized ) vaccine. Production of Mumpsvax as a stand-alone product ceased in 2009. The cells used in culture, virus stocks used, and animal fluids are all screened for extraneous material as part of

915-447: Is a neurological disorder that results from the demyelination of axons in the central nervous system. Some neurons do not generate action potentials but instead generate a graded electrical signal , which in turn causes graded neurotransmitter release. Such non-spiking neurons tend to be sensory neurons or interneurons, because they cannot carry signals long distances. Neural coding is concerned with how sensory and other information

976-496: Is a powerful electrical insulator , but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion channels that permit electrically charged ions to flow across the membrane and ion pumps that chemically transport ions from one side of the membrane to the other. Most ion channels are permeable only to specific types of ions. Some ion channels are voltage gated , meaning that they can be switched between open and closed states by altering

1037-625: Is a synapse in which a neuron's axon connects to its dendrites. The human brain has some 8.6 x 10 (eighty six billion) neurons. Each neuron has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 10 synapses (1 quadrillion). This number declines with age , stabilizing by adulthood. Estimates vary for an adult, ranging from 10 to 5 x 10 synapses (100 to 500 trillion). Beyond electrical and chemical signaling, studies suggest neurons in healthy human brains can also communicate through: They can also get modulated by input from

1098-419: Is common for neuroscientists to refer to cells that release glutamate as "excitatory neurons", and cells that release GABA as "inhibitory neurons". Some other types of neurons have consistent effects, for example, "excitatory" motor neurons in the spinal cord that release acetylcholine , and "inhibitory" spinal neurons that release glycine . The distinction between excitatory and inhibitory neurotransmitters

1159-478: Is not absolute. Rather, it depends on the class of chemical receptors present on the postsynaptic neuron. In principle, a single neuron, releasing a single neurotransmitter, can have excitatory effects on some targets, inhibitory effects on others, and modulatory effects on others still. For example, photoreceptor cells in the retina constantly release the neurotransmitter glutamate in the absence of light. So-called OFF bipolar cells are, like most neurons, excited by

1220-459: Is represented in the brain by neurons. The main goal of studying neural coding is to characterize the relationship between the stimulus and the individual or ensemble neuronal responses and the relationships among the electrical activities of the neurons within the ensemble. It is thought that neurons can encode both digital and analog information. The conduction of nerve impulses is an example of an all-or-none response. In other words, if

1281-432: Is transferred to the axon, which fires. If the pressure is steady, the stimulus ends; thus, these neurons typically respond with a transient depolarization during the initial deformation and again when the pressure is removed, which causes the corpuscle to change shape again. Other types of adaptation are important in extending the function of several other neurons. The German anatomist Heinrich Wilhelm Waldeyer introduced

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1342-643: Is used extensively by the Allen Institute for Brain Science . In 2023, a comprehensive cell atlas of the adult, and developing human brain at the transcriptional, epigenetic, and functional levels was created through an international collaboration of researchers using the most cutting-edge molecular biology approaches. Neurons communicate with each other via synapses , where either the axon terminal of one cell contacts another neuron's dendrite, soma, or, less commonly, axon. Neurons such as Purkinje cells in

1403-472: The glial cells that give them structural and metabolic support. The nervous system is made up of the central nervous system , which includes the brain and spinal cord , and the peripheral nervous system , which includes the autonomic , enteric and somatic nervous systems . In vertebrates, the majority of neurons belong to the central nervous system , but some reside in peripheral ganglia , and many sensory neurons are situated in sensory organs such as

1464-402: The retina and cochlea . Axons may bundle into nerve fascicles that make up the nerves in the peripheral nervous system (like strands of wire that make up a cable). In the central nervous system bundles of axons are called nerve tracts . Neurons are highly specialized for the processing and transmission of cellular signals. Given the diversity of functions performed in different parts of

1525-686: The squid giant axon could be used to study neuronal electrical properties. It is larger than but similar to human neurons, making it easier to study. By inserting electrodes into the squid giant axons, accurate measurements were made of the membrane potential . The cell membrane of the axon and soma contain voltage-gated ion channels that allow the neuron to generate and propagate an electrical signal (an action potential). Some neurons also generate subthreshold membrane potential oscillations . These signals are generated and propagated by charge-carrying ions including sodium (Na ), potassium (K ), chloride (Cl ), and calcium (Ca ) . Several stimuli can activate

1586-444: The synapse to another cell. Neurons may lack dendrites or have no axons. The term neurite is used to describe either a dendrite or an axon, particularly when the cell is undifferentiated . Most neurons receive signals via the dendrites and soma and send out signals down the axon. At the majority of synapses, signals cross from the axon of one neuron to the dendrite of another. However, synapses can connect an axon to another axon or

1647-409: The tubulin of microtubules . Class III β-tubulin is found almost exclusively in neurons. Actin is predominately found at the tips of axons and dendrites during neuronal development. There the actin dynamics can be modulated via an interplay with microtubule. There are different internal structural characteristics between axons and dendrites. Typical axons seldom contain ribosomes , except some in

1708-608: The JL1 strain was preferentially selected by propagation in Vero and chick embryo fibroblast (CEF) cell cultures . The JL2 strain was preferentially selected by passage in embryonated chicken eggs. In the US, the Jeryl Lynn strain-based vaccines supplanted the previous, killed virus, vaccine in 1978. Mumpsvax Mumps vaccines are vaccines which prevent mumps . When given to

1769-501: The MR (measles and rubella) mixed vaccine. No UK-licensed monovalent preparation was ever available. Monovalent mumps vaccines were available before MMR, but only used on a limited scale. This became the subject of considerable argument at the end of the 20th century, since some parents preferred to obtain individually the components of the MMR mixture. One mumps vaccine preparation imported into

1830-567: The United Kingdom and unlicensed, proved to be essentially ineffective. Immunisation against mumps in the UK became routine in 1988, commencing with MMR. The Aventis-Pasteur "MMR-2" brand is usual in the UK in 2006 . The cold chain is a major consideration in vaccination, particularly in less-developed countries. Mumps vaccines are normally refrigerated, but have a long half-life of 65 days at 23 degrees Celsius. Neuron Neurons are

1891-456: The adult brain may regenerate functional neurons throughout the life of an organism (see neurogenesis ). Astrocytes are star-shaped glial cells that have been observed to turn into neurons by virtue of their stem cell-like characteristic of pluripotency . Like all animal cells, the cell body of every neuron is enclosed by a plasma membrane , a bilayer of lipid molecules with many types of protein structures embedded in it. A lipid bilayer

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1952-429: The axon and activates synaptic connections as it reaches them. Synaptic signals may be excitatory or inhibitory , increasing or reducing the net voltage that reaches the soma. In most cases, neurons are generated by neural stem cells during brain development and childhood. Neurogenesis largely ceases during adulthood in most areas of the brain. Neurons are the primary components of the nervous system , along with

2013-584: The axon terminal, it opens voltage-gated calcium channels , allowing calcium ions to enter the terminal. Calcium causes synaptic vesicles filled with neurotransmitter molecules to fuse with the membrane, releasing their contents into the synaptic cleft. The neurotransmitters diffuse across the synaptic cleft and activate receptors on the postsynaptic neuron. High cytosolic calcium in the axon terminal triggers mitochondrial calcium uptake, which, in turn, activates mitochondrial energy metabolism to produce ATP to support continuous neurotransmission. An autapse

2074-438: The central nervous system and Schwann cells in the peripheral nervous system. The sheath enables action potentials to travel faster than in unmyelinated axons of the same diameter, whilst using less energy. The myelin sheath in peripheral nerves normally runs along the axon in sections about 1 mm long, punctuated by unsheathed nodes of Ranvier , which contain a high density of voltage-gated ion channels. Multiple sclerosis

2135-420: The central nervous system are typically only about one micrometer thick, while some in the peripheral nervous system are much thicker. The soma is usually about 10–25 micrometers in diameter and often is not much larger than the cell nucleus it contains. The longest axon of a human motor neuron can be over a meter long, reaching from the base of the spine to the toes. Sensory neurons can have axons that run from

2196-548: The cerebellum can have over 1000 dendritic branches, making connections with tens of thousands of other cells; other neurons, such as the magnocellular neurons of the supraoptic nucleus , have only one or two dendrites, each of which receives thousands of synapses. Synapses can be excitatory or inhibitory, either increasing or decreasing activity in the target neuron, respectively. Some neurons also communicate via electrical synapses, which are direct, electrically conductive junctions between cells. When an action potential reaches

2257-423: The disease; she became the namesake for the resulting Jeryl Lynn strain. Building on then-recent advances that had led to vaccines for polio and measles , the mumps virus strains were developed in embryonic hens' eggs and chick embryo cell cultures. The resulting strains of virus were less well-suited for human cells, and are thus said to be attenuated . They are sometimes referred to as neuroattenuated in

2318-551: The environment and hormones released from other parts of the organism, which could be influenced more or less directly by neurons. This also applies to neurotrophins such as BDNF . The gut microbiome is also connected with the brain. Neurons also communicate with microglia , the brain's main immune cells via specialized contact sites, called "somatic junctions". These connections enable microglia to constantly monitor and regulate neuronal functions, and exert neuroprotection when needed. In 1937 John Zachary Young suggested that

2379-477: The excitation from the OFF bipolar cells, silencing them. It is possible to identify the type of inhibitory effect a presynaptic neuron will have on a postsynaptic neuron, based on the proteins the presynaptic neuron expresses. Parvalbumin -expressing neurons typically dampen the output signal of the postsynaptic neuron in the visual cortex , whereas somatostatin -expressing neurons typically block dendritic inputs to

2440-486: The initial segment. Dendrites contain granular endoplasmic reticulum or ribosomes, in diminishing amounts as the distance from the cell body increases. Neurons vary in shape and size and can be classified by their morphology and function. The anatomist Camillo Golgi grouped neurons into two types; type I with long axons used to move signals over long distances and type II with short axons, which can often be confused with dendrites. Type I cells can be further classified by

2501-411: The location of the soma. The basic morphology of type I neurons, represented by spinal motor neurons , consists of a cell body called the soma and a long thin axon covered by a myelin sheath . The dendritic tree wraps around the cell body and receives signals from other neurons. The end of the axon has branching axon terminals that release neurotransmitters into a gap called the synaptic cleft between

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2562-609: The main components of nervous tissue in all animals except sponges and placozoans . Plants and fungi do not have nerve cells. Molecular evidence suggests that the ability to generate electric signals first appeared in evolution some 700 to 800 million years ago, during the Tonian period. Predecessors of neurons were the peptidergic secretory cells. They eventually gained new gene modules which enabled cells to create post-synaptic scaffolds and ion channels that generate fast electrical signals. The ability to generate electric signals

2623-402: The nervous system, there is a wide variety in their shape, size, and electrochemical properties. For instance, the soma of a neuron can vary from 4 to 100 micrometers in diameter. The accepted view of the neuron attributes dedicated functions to its various anatomical components; however, dendrites and axons often act in ways contrary to their so-called main function. Axons and dendrites in

2684-406: The object maintains even pressure, the neurons stop firing. The neurons of the skin and muscles that are responsive to pressure and vibration have filtering accessory structures that aid their function. The pacinian corpuscle is one such structure. It has concentric layers like an onion, which form around the axon terminal. When pressure is applied and the corpuscle is deformed, mechanical stimulus

2745-564: The phosphate backbone of the ribosomal RNA. The cell body of a neuron is supported by a complex mesh of structural proteins called neurofilaments , which together with neurotubules (neuronal microtubules) are assembled into larger neurofibrils. Some neurons also contain pigment granules, such as neuromelanin (a brownish-black pigment that is byproduct of synthesis of catecholamines ), and lipofuscin (a yellowish-brown pigment), both of which accumulate with age. Other structural proteins that are important for neuronal function are actin and

2806-467: The postsynaptic neuron. Neurons have intrinsic electroresponsive properties like intrinsic transmembrane voltage oscillatory patterns. So neurons can be classified according to their electrophysiological characteristics: Neurotransmitters are chemical messengers passed from one neuron to another neuron or to a muscle cell or gland cell . Since 2012 there has been a push from the cellular and computational neuroscience community to come up with

2867-474: The released glutamate. However, neighboring target neurons called ON bipolar cells are instead inhibited by glutamate, because they lack typical ionotropic glutamate receptors and instead express a class of inhibitory metabotropic glutamate receptors. When light is present, the photoreceptors cease releasing glutamate, which relieves the ON bipolar cells from inhibition, activating them; this simultaneously removes

2928-421: The same region of the brain or spinal cord. When multiple neurons are functionally connected together, they form what is called a neural circuit . A neuron contains all the structures of other cells such as a nucleus , mitochondria , and Golgi bodies but has additional unique structures such as an axon , and dendrites . The soma is a compact structure, and the axon and dendrites are filaments extruding from

2989-484: The sense that these strains are less virulent to human neurons than the wild strains. Hilleman's work led to the first effective mumps vaccine, called Mumpsvax. Licensed in 1967, its four-year development set a record for fastest development of a new vaccine, a record later surpassed by the COVID-19 vaccine , which was developed in less than a year. Vaccination against mumps did not become routine until Mumpsvax

3050-512: The silver staining technique used to visualize nervous tissue under light microscopy. The neuron's place as the primary functional unit of the nervous system was first recognized in the late 19th century through the work of the Spanish anatomist Santiago Ramón y Cajal . To make the structure of individual neurons visible, Ramón y Cajal improved a silver staining process that had been developed by Camillo Golgi . The improved process involves

3111-410: The site of injection and mild fever. More significant side effects are rare. Evidence is insufficient to link the vaccine to complications such as neurological effects. The vaccine should not be given to people who are pregnant or have very poor immune system function . Poor outcomes among children of mothers who received the vaccine during pregnancy, however, have not been documented. Even though

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3172-399: The soma. Dendrites typically branch profusely and extend a few hundred micrometers from the soma. The axon leaves the soma at a swelling called the axon hillock and travels for as far as 1 meter in humans or more in other species. It branches but usually maintains a constant diameter. At the farthest tip of the axon's branches are axon terminals , where the neuron can transmit a signal across

3233-695: The term neuron in 1891, based on the ancient Greek νεῦρον neuron 'sinew, cord, nerve'. The word was adopted in French with the spelling neurone . That spelling was also used by many writers in English, but has now become rare in American usage and uncommon in British usage. Some previous works used nerve cell ( cellule nervose ), as adopted in Camillo Golgi 's 1873 paper on the discovery of

3294-422: The terminals and the dendrites of the next neuron. Most neurons can be anatomically characterized as: Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are: Afferent and efferent also refer generally to neurons that, respectively, bring information to or send information from the brain. A neuron affects other neurons by releasing

3355-489: The toes to the posterior column of the spinal cord, over 1.5 meters in adults. Giraffes have single axons several meters in length running along the entire length of their necks. Much of what is known about axonal function comes from studying the squid giant axon , an ideal experimental preparation because of its relatively immense size (0.5–1 millimeter thick, several centimeters long). Fully differentiated neurons are permanently postmitotic however, stem cells present in

3416-514: The vaccine as part of their immunization programs. In areas where widespread vaccination is carried out it has resulted in a more than 90% decline in rates of disease. Almost half a billion doses of one variety of the vaccine has been given. In the mid-twentieth century, mumps infections among children were not viewed as a serious public health issue, but adult men may develop debilitating testicular inflammation, which posed particular difficulty among close-quartered soldiers during wartime. As

3477-447: The vaccine is developed in chicken cells, it is generally safe to give to those with egg allergies . Most of the developed world and many countries in the developing world include it in their immunization programs often in combination with measles and rubella vaccine known as MMR . A formulation with the previous three and the varicella (chickenpox) vaccine known as MMRV is also available. As of 2005, 110 countries provided

3538-513: The vaccine production. They are grown in Medium 199 (a solution containing buffered salt, vitamins, amino acids, fetal bovine serum) with SPGA (sucrose, phosphate, glutamate, human serum albumin ) and neomycin . The human albumin processing uses the Cohn cold ethanol fractionation method. Monovalent mumps vaccine (Mumpsvax) remained available in the US when MMR was introduced in the UK, replacing

3599-404: The voltage difference across the membrane. Others are chemically gated, meaning that they can be switched between open and closed states by interactions with chemicals that diffuse through the extracellular fluid. The ion materials include sodium , potassium , chloride , and calcium . The interactions between ion channels and ion pumps produce a voltage difference across the membrane, typically

3660-501: Was a key innovation in the evolution of the nervous system. Neurons are typically classified into three types based on their function. Sensory neurons respond to stimuli such as touch, sound, or light that affect the cells of the sensory organs , and they send signals to the spinal cord or brain . Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions to glandular output . Interneurons connect neurons to other neurons within

3721-457: Was included in Merck's combined MMR vaccine , which targeted measles and rubella along with mumps. MMR was licensed in 1971, and 40 percent of American children had received the combined vaccine by 1974. In 1977, the U.S. Centers for Disease Control and Prevention (CDC) recommended mumps immunization (as part of MMR) for all children over 12 months of age, and in 1998, CDC began recommending

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