69-498: Viola tricolor is a common European wild flower, growing as an annual or short-lived perennial . The species is also known as wild pansy , Johnny Jump up (though this name is also applied to similar species such as the yellow pansy), heartsease , heart's ease , heart's delight , tickle-my-fancy , Jack-jump-up-and-kiss-me , come-and-cuddle-me , three faces in a hood , love-in-idleness , and pink of my john . It has been introduced into North America, where it has spread. It
138-472: A higher persistence of soil seed banks . These differences in life history strategies profoundly affect ecosystem functioning and services. For instance, annuals, by allocating less resources belowground, play a more minor role in reducing erosion, storing organic carbon, and achieving lower nutrient- and water-use efficiencies than perennials. The distinctions between annual and perennial plants are notably evident in agricultural contexts. Despite constituting
207-488: A lesser extent the flowers and stems, are also a known emetic and purgative/laxative , and should be used with caution. The ancient Chinese used the plant as medicine, and the Celts and Romans made perfumes of them. The flowers have also been used to make yellow, green and blue-green dyes, while the leaves can be used to indicate acidity . The plant, especially the flowers, contains antioxidants , has low toxicity, and
276-422: A major role in immune system function. Wider blood vessels allow more blood containing immune cells and proteins to reach the infection site. Vasodilation occurs as part of the process of inflammation , which is caused by several factors including presence of a pathogen, injury to tissues or blood vessels, and immune complexes . In severe cases, inflammation can lead to sepsis or distributive shock. Vasodilation
345-466: A metaphor of growing older as her confidence and her vision increases. The heartsease is known as love-lies-bleeding which is a type of the inseparability of the pain of living and the love of Christ. The garden was adorned with the flower which served as the speaker's life. The "weed" represents the sins of the speaker's life. However at the end, the speaker pleads her pain and waits her judgment. Heartsease I found, where Love-lies-bleeding Empurpled all
414-682: A minor part of global biomass, annual species stand out as the primary food source for humankind, likely owing to their greater allocation of resources to seed production, thereby enhancing agricultural productivity. In the Anthropocene epoch, marked by human impact on the environment, there has been a substantial increase in the global cover of annuals. This shift is primarily attributed to the conversion of natural systems, often dominated by perennials, into annual cropland. Currently, annual plants cover approximately 70% of croplands and contribute to around 80% of worldwide food consumption. In 2008, it
483-502: A perennial life cycle are twice as fast as the reverse transition. The life-history theory posits that annual plants are favored when adult mortality is higher than seedling (or seed) mortality, i.e., annuals will dominate environments with disturbances or high temporal variability, reducing adult survival. This hypothesis finds support in observations of increased prevalence of annuals in regions with hot-dry summers, with elevated adult mortality and high seed persistence. Furthermore,
552-417: A potent vasoconstrictor. Epinephrine , either exogenous or endogenous, is another vasoconstrictor released by the adrenal glands in response to stress. It binds to α and β adrenergic receptors like norepinephrine , causing vasodilation and vasoconstriction in different body parts to redistribute circulation to critical areas. Cold-induced vasodilation (CIVD) occurs after cold exposure, possibly to reduce
621-543: A potential treatment for autoimmune disorders . The extract is known to be antimicrobial , sedative , antiepileptic , and diuretic , as well as potentially antiviral and antiprotozoal . V. tricolor L extract has shown vasorelaxant , cardio-relaxant, hypotensive, and cardio protective effects. Some studies have discovered potential anti-cancer properties, where the extract (primarily the ethyl acetate component) has been attributed to induced apoptosis and inhibited angiogenesis in cancer cells. The seeds and roots, and to
690-477: A rise in MAP. Arterioles create the most vascular resistance of any blood vessel type, as they are very narrow and possess concentric layers of smooth muscle unlike venules and capillaries . Vasodilation occurs in superficial blood vessels of warm-blooded animals when their ambient environment is hot; this process diverts the flow of heated blood to the skin of the animal, where heat can be more easily released to
759-601: A unique scenario unfolds: when annuals establish dominance, perennials do not necessarily supplant them. This peculiarity is attributed to alternative stable states in the system—both annual dominance and perennial states prove stable, with the ultimate system state dependent on the initial conditions. Annual plants commonly exhibit a higher growth rate, allocate more resources to seeds, and allocate fewer resources to roots than perennials. In contrast to perennials, which feature long-lived plants and short-lived seeds, annual plants compensate for their lower longevity by maintaining
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#1732797637561828-419: A weighted average of systolic and diastolic blood pressures, and is a better measurement of perfusion over the duration of the cardiac cycle. Vasodilation works to decrease vascular resistance and blood pressure through relaxation of smooth muscle cells in the tunica media layer of large arteries and smaller arterioles. When vasodilation causes systolic blood pressure to fall below 90 mmHg, circulatory shock
897-452: Is also a major component of anaphylaxis . Inflammation causes not only vasodilation but also causes increased vascular permeability , allowing neutrophils , complement proteins , and antibodies to reach the site of infection or damage. Elevated vascular permeability can allow excess fluid to leave blood vessels and collect in tissues resulting in edema ; vasodilation prevents blood vessels from constricting to adapt to reduced volume in
966-521: Is also found on the banks and in the alluviums . In Iceland, Viola tricolor is known to be a host for at least two species of plant pathogenic fungi , Pleospora herbarum and Ramularia agrestis . As an ornamental and medicinal plant , the wild pansy has been cultivated since the Middle Ages and bred in Britain since 1810. As some of its names imply, V. tricolor and other plants in
1035-522: Is called "Heart's Ease". Long before cultivated pansies were released into the trade in 1839 , V. tricolor was associated with thought in the " language of flowers ", often by its alternative name of pansy (from the French pensée , "thought"): hence Ophelia's often quoted line in Shakespeare's Hamlet , "There's pansies, that's for thoughts". (What Shakespeare had in mind was V. tricolor ,
1104-440: Is caused by myosin-light-chain phosphatase , which dephosphorylates the myosin light chain causing muscle relaxation. Smooth muscle cells can remain contracted without use of ATP due to action of the myosin-binding subunit of myosin light-chain phosphatase. Phosphorylation of this subunit by Rho-kinase prevents it from binding to and dephosphorylating the myosin light-chain, allowing the cell to remain contracted. Vasodilation
1173-875: Is edible. V tricolor leaves, stems, roots and flowers have been found to contain antioxidants and flavonoids (including violanthin, violaquercitrin, quercetin, luteolin, and rutin ), amino acids, chlorogenic acids, salicylates, as well as alkaloids, volatile oils, mucilage gums, resin, saponins, and vitamins A and C. Various carotenoids have also been isolated from the drug, including violaxanthin , antheraxanthin , lutein , zeaxanthin and beta-Carotene . The fresh plant Viola declinata and V. tricolor contains approximately: Its 10 percent mucilages consist of glucose , galactose , arabinose and rhamnose , as well as tannins , salicylic acid , and its derivatives. Anthocyanidins and coumarins , such as umbelliferone , were also detected in Viola tricolor. Extracts from
1242-459: Is necessary to understand the causes and impacts of vasodilation. Cardiac output is defined as the amount of blood pumped through the heart over 1 minute, in units of liters per minute, equal to heart rate multiplied by stroke volume . It is directly related to heart rate , myocardial contractility , and preload , and inversely related with afterload . Elevated vascular resistance due to constricted blood vessels causes in increase in afterload,
1311-436: Is observed. Vascular resistance depends on several factors, including the length of the vessel, the viscosity of blood (determined by hematocrit ) and the diameter of the blood vessel. The latter is the most important variable in determining resistance, with the vascular resistance changing by the fourth power of the radius. An increase in either of these physiological components (cardiac output or vascular resistance) causes
1380-489: Is of the rhizome type with fine rootlets. The stem (acoli stem: which remains flush with the soil and from which leave the leaves and the flowering stalk) is hairless, sometimes downy and is branched. The plant has no leaf rosette at the base, unlike some other violets, such as Viola hirta . Leaves are, on the contrary, alternate. They are stalked at limbus oval, oblong or lanceolate and more or less serrated margins. The stipules are often quite developed, at least those of
1449-542: Is one of many viola plant species containing cyclotides . These small peptides have proven to be useful in drug development due to their size and structure giving rise to high stability. Many cyclotides found in Viola tricolor are cytotoxic . This feature means it could be used to treat cancers . According to Roman mythology , the wild pansy turned into the Love-in-idleness as Cupid shot one of his arrows at
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#17327976375611518-803: Is quickly broken down, diffused, or undergoes reuptake, impacts are brief and localized endothelium- possible role as mediator of hyperpolarization of smooth muscle cells co-released with norepinephrine Also worthy of mention when discussing neural control of vasodilation is the renin-angiotensin-aldosterone system, or RAAS. The kidneys retain water by reabsorbing sodium ions, or eliminate water by eliminating sodium ions. Sympathetic nervous system activity, reduced blood volume or reduced arterial pressure trigger β-adrenergic receptors in select kidney cells to release renin , which converts facilitates formation of angiotensin II from its substrate angiotensin . Angiotensin II triggers adrenal glands to secrete aldosterone ,
1587-749: Is simply the result of insufficient neurotransmitter to maintain basal neural tone, without the presence of a compound directly causing vasodilation. Neurotransmitters can act by binding directly to smooth muscle cells or by binding to endothelial cells mediating the effects of the neurotransmitter. Below is a table summarizing major neurotransmitters involved in regulation of the vasculature. α1- smooth muscle α2- endothelial β1, β2- smooth muscle α2- inhibit cAMP, release NO, vasodilation β1, β2- possible vasodilation muscanaric Ach receptors (mAchRs) - on both endothelial and smooth muscle cells mAchRs- endothelial M3 AchR release NO, vasodlation smooth muscle M2 and M3 AchRs reduce release NO, vasoconstriction Note: Ach
1656-547: Is the most sought after. It flowers from April to September (in the Northern Hemisphere). The plants are hermaphroditic and self-fertile, pollinated by bees. It is common almost everywhere on the Eurasian continent, near the sea or inland, at altitudes ranging from 0 to 2,700 metres (8,900 ft). It grows in open grasslands , wastelands, mainly on acidic or neutral soils and usually in partial shade. It
1725-481: Is the progenitor of the cultivated pansy , and is therefore sometimes called wild pansy ; before the cultivated pansies were developed, "pansy" was an alternative name for the wild form. It can produce up to 50 seeds at a time. The flowers can be purple, blue, yellow or white. Viola tricolor is a small plant of creeping and ramping habit, reaching at most 15 centimetres (6 in) in height, with flowers about 1.5 cm ( 1 ⁄ 2 in) in diameter. Its root
1794-614: Is the result of relaxation in smooth muscle surrounding the blood vessels. This relaxation, in turn, relies on removing the stimulus for contraction, which depends on intracellular calcium ion concentrations and is tightly linked with phosphorylation of the light chain of the contractile protein myosin . Thus, vasodilation works mainly either by lowering intracellular calcium concentration or by dephosphorylation (really substitution of ATP for ADP) of myosin. Dephosphorylation by myosin light-chain phosphatase and induction of calcium symporters and antiporters that pump calcium ions out of
1863-430: Is the widening of blood vessels . It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins , large arteries , and smaller arterioles . Blood vessel walls are composed of endothelial tissue and a basal membrane lining the lumen of the vessel, concentric smooth muscle layers on top of endothelial tissue, and an adventitia over the smooth muscle layers. Relaxation of
1932-647: The Viola genus (such as V. odorata , or sweet violet), have a long history of use in herbalism and folk medicine , particularly Iranian, Greco-Arab, Ayurvedic and Unani traditional health systems. Traditionally, it has been used to treat cardiovascular conditions, epilepsy , skin diseases, burns and eczema , and as an expectorant for respiratory problems such as bronchitis , asthma , and cold symptoms, and modern research has begun to corroborate these traditionally held knowledges and uses. Studies have shown V. tricolor extract has antinociceptive , immunosuppressant and anti-inflammatory properties, making it
2001-649: The autonomic nervous system Baroreceptors sense blood pressure and allow adaptation via the mechanisms of vasoconstriction or vasodilation to maintain homeostasis . The primary function of vasodilation is to increase blood flow in the body to tissues that need it most. This is often in response to a localized need for oxygen but can occur when the tissue in question is not receiving enough glucose , lipids , or other nutrients . Vasodilation, both localized and systemic, also facilitates immune response. Localized tissues have multiple ways to increase blood flow, including releasing vasodilators, primarily adenosine , into
2070-637: The brain stem or spinal cord; it contains both sensor and motor nerves. The two divisions of the ANS, the sympathetic nervous system (SNS) and the parasympathetic nervous system (PSNS), impact blood vessels differently. Traditionally we understand that these two divisions work against each other, the SNS producing "fight or flight" and the PSNS producing "rest and digest", but in the case of vascular innervation this line becomes blurred ANS nerves do not directly innervate
2139-461: The above mechanisms may be grouped as endogenous and exogenous . The vasodilating action of activation of beta-2 receptors (such as by adrenaline) appears to be endothelium -independent. As referenced in the explanation of smooth muscle physiology, smooth muscle within the tunica media is innervated by the autonomic nervous system. The autonomic nervous system (ANS) controls essential involuntary body functions and originates as nerves leaving
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2208-478: The amount of force against which the heart must contract. Vasodilation therefore decreases vascular resistance, which decreases afterload, elevating cardiac output and allowing perfusion of tissues. Blood pressure measures how much pressure blood exerts on blood vessel walls; systolic blood pressure measures pressure while the heart contracts ( systole ), and diastolic blood pressure reflects pressure between contractions ( diastole ). Mean arterial pressure (MAP)is
2277-475: The amount of force circulating blood must overcome in order to allow perfusion of body tissues. Narrow vessels create more vascular resistance, while dilated vessels decrease vascular resistance. Vasodilation acts to increase cardiac output by decreasing afterload , −one of the four determinants of cardiac output. By expanding available area for blood to circulate, vasodilation decreases blood pressure . The response may be intrinsic (due to local processes in
2346-790: The blood vessel via diapedesis . Anaphylaxis is a severe allergic reaction characterized by elevated vascular permeability, systemic vasodilation, gastrointestinal dysfunction, and respiratory dysfunction. Anaphylatoxins , specifically complement proteins C3a and C5a, bind to receptors on mast cells and basophils causing degranulation . Granules in these cells contain histamine , platelet-activating factor , and other compounds causing clinical manifestation of anaphylaxis- including systemic vasodilation causing dangerously low blood pressure. Immunoglobulin E , an antibody produced by plasma cells , also binds to receptors on mast cells and basophils causing degranulation. A basic understanding of cardiac output , vascular resistance , and blood pressure
2415-457: The bolt of Cupid fell: It fell upon a little western flower, Before, milk-white, now purple with love's wound, And maidens call it love-in-idleness. A Midsummer Night's Dream (Act 2, Scene 1) The love-in-idleness was originally a white flower, struck by one of Cupid's arrows, which turned it purple and gave it its magic love potion. When dripped onto someone's eyelids this love potion causes an individual to fall madly in love with
2484-421: The cytosol, either via Ca,Mg-ATPase from the sarcoplasmic reticulum or voltage-gated calcium channels from the extracellular matrix. Calcium ions bind with calmodulin , activating myosin light-chain kinase which phosphorylates the myosin light-chain. Phosphorylated light-chain myosin interacts with actin filaments forming a cross-bridge , allowing muscle contraction causing vasoconstriction. Vasodilation
2553-651: The effect of love-in-idleness - alluding to its qualities to simulate the effects of love. O Tranio! till I found it to be true, I never thought it possible or likely; But see, while idly I stood looking on, I found the effect of love in idleness; And now in plainness do confess to thee, That art to me as secret and as dear As Anna to the Queen of Carthage was, Tranio, I burn, I pine, I perish, Tranio, If I achieve not this young modest girl. In her poem Balm in Gilead , Christina Georgina Rossetti uses heartsease as
2622-428: The environment. The opposite physiological process is vasoconstriction . These processes are naturally modulated by local paracrine agents from endothelial cells (e.g., nitric oxide , bradykinin , potassium ions , and adenosine ), and by the autonomic nervous system and the adrenal glands , both of which secrete catecholamines , such as norepinephrine and epinephrine , respectively. The tunica media of
2691-404: The evolution of the annual life cycle under hot-dry summer in different families makes it one of the best examples of convergent evolution . Additionally, annual prevalence is also positively affected by year-to-year variability. Globally, the prevalence of annual plants shows an upward trend with an increasing human footprint. Moreover, domestic grazing has been identified as contributing to
2760-410: The fact that those can lead to foolish and hurtful things and present the idea that love can also end in tragedy. The play shows that love can be a source of comedy as easily as of tragedy and therefore show that the power that the love potion from the Love-in-idleness inherits is beyond the comprehension of the fairies and mortals. In the end, the love-in-idleness nectar is used to restore all romances in
2829-437: The flower to provide the essential dramatic and comical features for his play. Besides that the love potion gained from the flower, does not only interfere with the lovers' fates, but also gives the play structure as it affects the lovers' romances drastically, as it at first upsets the balance of love and creates asymmetrical love among the four Athenian lovers. The fact that this flower introduces magical love to this play creates
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2898-458: The girl into a heifer and kept her grazing at his feet. For pity on the diet of herbs to which he submitted the beloved, he caused the earth to produce beautiful flowers that he called Io. Another Greek legend has it that the delicate white flowers were worshiped by Eros . To inhibit this worship, Aphrodite colored them, which resulted in tricolor coloration. No. 1 of 3 Lyrics , H. 161, written for piano in 1921 by British composer Frank Bridge ,
2967-428: The ground: Whatever flowers I missed unheeding, Heartsease I found. Yet still my garden mound Stood sore in need of watering, weeding, And binding growths unbound. Ah, when shades fell to light succeeding I scarcely dared look round: 'Love-lies-bleeding' was all my pleading, Heartsease I found. Annual plant An annual plant is a plant that completes its life cycle , from germination to
3036-496: The hand, the blood vessels in the finger tips will suddenly vasodilate. This is probably caused by a sudden decrease in the release of neurotransmitters from the sympathetic nerves to the muscular coat of the arteriovenous anastomoses due to local cold. The CIVD increases blood flow and subsequently the temperature of the fingers. This can be painful and is sometimes known as the ' hot aches ' which can be painful enough to bring on vomiting. A new phase of vasoconstriction follows
3105-702: The heightened abundance of annuals in grasslands. Disturbances linked to activities like grazing and agriculture, particularly following European settlement, have facilitated the invasion of annual species from Europe and Asia into the New World. In various ecosystems, the dominance of annual plants is often a temporary phase during secondary succession , particularly in the aftermath of disturbances. For instance, after fields are abandoned, annuals may initially colonize them but are eventually replaced by long-lived species. However, in certain Mediterranean systems,
3174-415: The imperial votaress, but missed and instead struck it. As Cupid is the god of desire, affection and erotic love, the flower's juice received the trait, to act as a love potion . Its name relates to the use of the flower, as it is often used for idleness or vileness acts. According to Greek mythology , Zeus fell in love with a young woman named Io and provoked jealousy to his wife Hera . He transformed
3243-419: The infection site via a process called leukocyte extravasation . Vasodilation allows the same volume of blood to move more slowly according to the flow rate equation Q = Av, where Q represents flow rate, A represents cross-sectional area, and v represents velocity. Immune effector cells can more easily attach to selectins expressed on endothelial cells when blood is flowing slowly, enabling these cells to exit
3312-540: The intracellular compartment both contribute to smooth muscle cell relaxation and therefore vasodilation. This is accomplished through reuptake of ions into the sarcoplasmic reticulum via exchangers and expulsion across the plasma membrane. There are three main intracellular stimuli that can result in the vasodilation of blood vessels. The specific mechanisms to accomplish these effects vary from vasodilator to vasodilator. PDE5 inhibitors and potassium channel openers can also have similar results. Compounds that mediate
3381-497: The local interstitial fluid , which diffuses to capillary beds, provoking local vasodilation. Some physiologists have suggested that it is the lack of oxygen itself that causes capillary beds to vasodilate by the smooth muscle hypoxia of the vessels in the region. This latter hypothesis is posited due to the presence of precapillary sphincters in capillary beds. These approaches to the mechanism of vasodilation have not been found to be mutually exclusive . Vasodilation plays
3450-474: The lovers' story as a comedy, with the inclusion of several tragic and dramatic moments. This is supposed to show that love can be a source of comedy as easily as of tragedy, and therefore show that the power that the love potion from the love-in-idleness inherits is beyond the comprehension of fairies and mortals alike. Shakespeare mentions it in his play The Taming of the Shrew where Luciento claims he found
3519-404: The next person they see. In A Midsummer Night's Dream , William Shakespeare uses this flower as a plot device to introduce the comical disturbance and chaos of love, but also to highlight the irrationality of romantic love. Here love is depicted as a sort of benevolent affliction. Shakespeare presents love to be something contradicting to one's normal feelings and ideas. However he also depicts
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#17327976375613588-464: The plant "before milk-white, now purple with love's wound". The "imperial vot'ress" passes on "fancy-free", destined never to fall in love. In Act II and III, Oberon 's and Puck 's intervention with the magic love potion of the flower, they can control the fates of various characters, but also speed up the process of falling in and out of love, so that the actual romances of the lovers and their love itself appears to become very comical. Shakespeare uses
3657-484: The plant are anti-microbial . Heartsease contains compounds, including colorless crystalline compounds, proven to be useful in prophylaxis and treatment of some medical conditions (see Traditional and Medicinal Uses section), such as cardiovascular problems, complications of diabetes , inflammations, immune disorders, and liver problems, among other indications. Heartsease plants contain aglycones apigenin , chrysoeriol, isorhamnetin , kaempferol . V. tricolor
3726-410: The play to their original states (including Demetrius's prior affections for Helena before he turned to Hermia.) The effects of the love-in-idleness can be very dramatic and tragic, no matter if the intentions were right. The play reaches its point at which Demetrius and Lysander are trying to kill one another. Although Hermia and Helena are not trying to kill one another, they are suffering from
3795-408: The potential for many possible outcomes for this play. The juice of the heartsease now, claims Oberon, "on sleeping eyelids laid, Will make or man or woman madly dote Upon the next live creature that it sees." Equipped with such powers, Oberon and Puck control the fates of various characters in the play to provide Shakespeare's essential dramatic and comic structure for the play. Yet mark'd I where
3864-610: The production of seeds , within one growing season , and then dies. Globally, 6% of all plant species and 15% of herbaceous plants (excluding trees and shrubs) are annuals. The annual life cycle has independently emerged in over 120 different plant families throughout the entire angiosperm phylogeny. Traditionally, there has been a prevailing assumption that annuals have evolved from perennial ancestors. However, recent research challenges this notion, revealing instances where perennials have evolved from annual ancestors. Intriguingly, models propose that transition rates from an annual to
3933-407: The rejection of their lovers and from considerable verbal abuse. However, this still happens at a very comical level, for the lovers are not aware of their situation. The more they try to present the dramatic side of love, the hate, jealousy and anger, the less they become serious, and so their anger turns unreal. In the end, love is not denied and the lovers are reunited. Nevertheless, Shakespeare ends
4002-406: The risk of injury. It can take place in several locations in the human body but is observed most often in the extremities. The fingers are especially common because they are exposed most often. When the fingers are exposed to cold, vasoconstriction occurs first to reduce heat loss, resulting in strong cooling of the fingers. Approximately five to ten minutes after the start of the cold exposure of
4071-399: The smooth muscle layer allows the blood vessel to dilate, as it is held in a semi-constricted state by sympathetic nervous system activity. Vasodilation is the opposite of vasoconstriction , which is the narrowing of blood vessels. When blood vessels dilate , the flow of blood is increased due to a decrease in vascular resistance and increase in cardiac output . Vascular resistance is
4140-488: The surrounding tissue ) or extrinsic (due to hormones or the nervous system ). In addition, the response may be localized to a specific organ (depending on the metabolic needs of a particular tissue, as during strenuous exercise), or it may be systemic (seen throughout the entire systemic circulation ). Endogenous substances and drugs that cause vasodilation are termed vasodilators. Many of these substances are neurotransmitters released by perivascular nerves of
4209-455: The upper leaves. These stipules are palm-lined or palmatised. The flowers are solitary and lateral, hoisted on long peduncles . They appear on aerial stems with more or less long internodes . The sepals are never larger than the corolla. It is 10 to 25 millimetres ( 3 ⁄ 8 to 1 in) long. This corolla can be purple, blue, yellow or white. It can most often be two-tone, yellow and purple. The tricolor shape, yellow, white and purple,
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#17327976375614278-478: The vasculature via synapses with muscle cells; instead, they release neurotransmitters that reach target cells and effect smooth muscle contraction or relaxation. Physical characteristics of the SNS and PSNS cause the SNS to have a prolonged, systemic impact on blood vessels, while the PSNS causes short-lived, localized change. SNS stimulation causes a base level of vasoconstriction often referred to as basal neural tone, maintaining blood pressure. Often vasodilation
4347-481: The vasodilation, after which the process repeats itself. This is called the Hunting reaction . Experiments have shown that three other vascular responses to immersion of the finger in cold water are possible: a continuous state of vasoconstriction; slow, steady, and continuous rewarming; and a proportional control form in which the blood vessel diameter remains constant after an initial phase of vasoconstriction. However,
4416-460: The vast majority of responses can be classified as the Hunting reaction. These drugs can keep vessels staying opened or help vessels refrain from being narrowed. Drugs that appear to work by activating the α 2A receptors in the brain thereby decreasing sympathetic nervous system activity. Directly relax the muscle in the walls of the blood vessels (especially the arterioles), allowing
4485-524: The vessel to dilate (widen). Vasodilators are used to treat conditions such as hypertension , wherein the patient has an abnormally high blood pressure, as well as angina , congestive heart failure , and erectile dysfunction , and where maintaining a lower blood pressure reduces the patient's risk of developing other cardiac problems. Flushing may be a physiological response to vasodilators. Some phosphodiesterase inhibitors such as sildenafil , vardenafil and tadalafil , work to increase blood flow in
4554-658: The vessels, causing low blood pressure and septic shock . In the case of inflammation, vasodilation is caused by cytokines . Interferon gamma , TNF-a , interleukin 1 beta , and interleukin 12 are a few examples of some inflammatory cytokines produced by immune cells such as natural killer cells , B cells , T cells , mast cells and macrophages . Anti-inflammatory cytokines that regulate inflammation and help prevent negative results such as septic shock are also produced by these immune cells. Vasodilation and increased vascular permeability also allow immune effector cells to leave blood vessels and follow chemoattractants to
4623-403: The walls of arteries, arterioles, and veins is composed of smooth muscle and causes vasodilation and vasoconstriction. Contraction of smooth muscle cells causes vasoconstriction, and relaxation of smooth muscle causes vasodilation. Smooth muscle is innervated by the autonomic nervous system and is non-striated (does not contain sarcomeres). Contraction is dependent on concentrations of Ca in
4692-402: The wild pansy, not a modern garden pansy.) Shakespeare makes a more direct reference, probably to V. tricolor in A Midsummer Night's Dream . Oberon sends Puck to gather "a little western flower that maidens call love-in-idleness". Oberon's account is that he diverted an arrow from Cupid's bow aimed at "a fair vestal , throned by the west" (supposedly Queen Elizabeth I) to fall upon
4761-457: Was discovered that the inactivation of only two genes in one species of annual plant leads to its conversion into a perennial plant . Researchers deactivated the SOC1 and FUL genes (which control flowering time) of Arabidopsis thaliana . This switch established phenotypes common in perennial plants, such as wood formation. Vasodilation Vasodilation , also known as vasorelaxation ,
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