Vasodilation 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, smaller arterioles; the process is the opposite of vasoconstriction, 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. Therefore, dilation of arterial blood vessels decreases blood pressure; the response may be extrinsic. In addition, the response may be localized to a specific organ. Endogenous substances and drugs that cause vasodilation are termed vasodilators; such vasoactivity is necessary for homeostasis. The primary function of vasodilation is to increase blood flow in the body to tissues that need it most; this is 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. Localized tissues have multiple ways to increase blood flow, including releasing vasodilators adenosine, into 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 are not mutually exclusive. Vasodilation directly affects the relationship between mean arterial pressure, cardiac output, total peripheral resistance. Vasodilation occurs in the time phase of cardiac systole, whereas vasoconstriction follows in the opposite time phase of cardiac diastole. Cardiac output is computed by multiplying the stroke volume. TPR depends on several factors, including the length of the vessel, the viscosity of blood and the diameter of the blood vessel; the latter is the most important variable in determining resistance, with the TPR changing by the fourth power of the radius. An increase in either of these physiological components causes a rise in the mean arterial pressure.
Vasodilation works to decrease TPR and blood pressure through relaxation of smooth muscle cells in the tunica media layer of large arteries and smaller arterioles. Vasodilation occurs in superficial blood vessels of warm-blooded animals when their ambient environment is hot; the opposite physiological process is vasoconstriction. These processes are modulated by local paracrine agents from endothelial cells, as well as an organism's autonomic nervous system and adrenal glands, both of which secrete catecholamines such as norepinephrine and epinephrine, respectively. Vasodilation 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 linked with phosphorylation of the light chain of the contractile protein myosin. Thus, vasodilation works either by lowering intracellular calcium concentration or by dephosphorylation of myosin. Dephosphorylation by myosin light-chain phosphatase and induction of calcium symporters and antiporters that pump calcium ions out of 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; the specific mechanisms to accomplish these effects vary from vasodilator to vasodilator. PDE5 inhibitors and potassium channel openers can have similar results. Compounds that mediate the above mechanisms may be grouped as exogenous; the vasodilating action of activation of beta-2 receptors appears to be endothelium-independent. Although it is recognized that the sympathetic nervous system plays an expendable role in vasodilation, it is only one of the mechanisms by which vasodilation can be accomplished; the spinal cord has both vasoconstriction nerves. The neurons that control vascular vasodilation originate in the hypothalamus; some sympathetic stimulation of arterioles in skeletal muscle is mediated by epinephrine acting on β-adrenergic receptors of arteriolar smooth muscle, which would be mediated by cAMP pathways, as discussed above.
However, it has been shown that knocking out this sympathetic stimulation plays little or no role in whether skeletal muscle is able to receive sufficient oxygen at high levels of exertion, so it is believed that this particular method of vasodilation is of little importance to human physiology. In cases of emotional distress, this system may activate, resulting in fainting due to decreased blood pressure from vasodilation, referred to as vasovagal syncope. Cold-induced vasodilation occurs after cold exposure to reduce the risk of injury, it can take place in se
Johnny Hawksworth was a British musician and composer who had lived and worked in Australia since 1984. Hawksworth trained as a pianist, but played double bass for Britain's leading big band the Ted Heath Orchestra during the early 1950s and through the 1960s. During this time he became one of the most popular jazz bassists in the UK, winning many polls and was featured as a soloist on Heath concerts and recordings, he is best known, for his short compositions for television. These include Salute to Thames and the theme tunes for the 1960s pop music show Thank Your Lucky Stars and the 1970s series Roobarb, Man About the House and George and Mildred, he contributed some of the incidental music used in the 1967 Spider-Man cartoon In addition to his television themes, he worked on films, including the scores to The Naked World of Harrison Marks, The Penthouse, Zeta One. "Er Indoors", one of his compositions, saw frequent use in the Nickelodeon TV Series SpongeBob SquarePants, in which it was associated with Avid Spongebob fan Patchy the Pirate.
Hawksworth has written many pieces of stock music for the De Wolfe Music library. He provided the hypnotic musical soundtrack to Geoffrey Jones' classic British Transport Film "Snow". Johnny Hawksworth discography at Discogs Johnny Hawksworth on IMDb Johnny Hawksworth on Facebook
The law school of Beirut was a center for the study of Roman law located in Berytus during late antiquity. It flourished under the patronage of the Roman emperors and functioned as the Roman Empire's preeminent center of jurisprudence until its destruction in AD 551; the law schools of the Roman Empire established organized repositories of imperial constitutions and institutionalized the study and practice of jurisprudence to relieve the busy imperial courts. The archiving of imperial constitutions facilitated the task of jurists in referring to legal precedents; the origins of the law school of Beirut are obscure, but it was under Augustus in the first century. The earliest written mention of the school dates to 238–239 AD, when its reputation had been established; the school attracted young, affluent Roman citizens, its professors made major contributions to the Codex of Justinian. The school achieved such wide recognition throughout the Empire that Beirut was known as the "Mother of Laws".
Beirut was one of the few schools allowed to continue teaching jurisprudence when Byzantine emperor Justinian I shut down other provincial law schools. The course of study at Beirut lasted for five years and consisted in the revision and analysis of classical legal texts and imperial constitutions, in addition to case discussions. Justinian took a personal interest in the teaching process, charging the bishop of Beirut, the governor of Phoenicia Maritima and the teachers with discipline maintenance in the school; the school's facilities were destroyed in the aftermath of a massive earthquake that hit the Phoenician coastline. It was moved to Sidon but did not survive the Arab conquest of 635 AD. Ancient texts attest that the school was next to the ancient Anastasis church, vestiges of which lie beneath the Saint George Greek Orthodox Cathedral in Beirut's historic center; as the guarantor of justice, the Roman emperor was expected to devote substantial amounts of time to judicial matters. He was the chief magistrate whose major prerogative was the ordering of all public affairs, for which he could demand assistance from anyone at any time.
With legal appeals, petitions from subjects and judicial queries of magistrates and governors, the emperors were careful to consult with the jurists, who were secretaries drafted from the equestrian order. From the reign of Augustus, jurists began compiling organized repositories of imperial edicts, legal scholarship became an imperially sponsored function of administration; every new judicial decision was founded on earlier deliberations. The edict repositories and the imperially sponsored legal scholarship gave rise to the earliest law school system of the Western world, aimed at training professional jurists. During the reign of Augustus, Beirut was established under the name Colonia Iulia Augusta Felix Berytus as a colony for Battle of Actium veterans from the fifth Macedonian and the third Gallic legions, it was chosen as a regional center instead of the more prominent Phoenician cities of Tyre and Sidon, which had a history of belligerence against Rome. Beirut was first mentioned in writing as a major center for the study of law in the 239 works of Gregory Thaumaturgus, the bishop of Neo-Caesarea.
Other early written sources do not mention when the law school was established, the date is much debated among modern historians and scholars. Edward Gibbon suggested its founding may have been directed by locally born Emperor Alexander Severus, who reigned during AD 222–235. Italian jurist Scipione Gentili, attributed the school's foundation to Augustus, while 19th-century German theologian Karl Hase advocated its establishment shortly after the victory at Actium. Adolf Friedrich Rudorff dated it to the reign of Hadrian, while Franz Peter Bremer suggested that it opened around 200, based on Thaumaturgus. Theodor Mommsen linked the establishment of the law school in Beirut with the need for jurists, since the city was chosen to serve as a repository for Roman imperial edicts concerning the eastern provinces. After arriving in Beirut, these were translated into Greek and archived; this function was first recorded in 196 AD, the date of the earliest constitutions contained in the Gregorian Codex, but the city is thought to have served as a repository since earlier times.
The proximity of the repository to the law school allowed the Beiruti jurists to consult archived documents and for students to learn of the most recent imperial decrees—an advantage that the law schools of Caesarea Maritima and Alexandria lacked. The 3rd-century emperors Diocletian and Maximian issued constitutions exempting the students of the law school of Beirut from compulsory service in their hometowns. In the 4th century, the Greek rhetorician Libanius reported that the school attracted young students from affluent families and deplored the school's instructional use of Latin, abandoned in favor of Greek in the course of the century. By the 5th century, Beirut had established its leading position and repute among the Empire's law schools. From 425, the law school of Constantinople became a rival center of law study and was the only school, along with Beirut's, to be maintained after Justinian I closed those of Alexandria, Caesarea Maritima and Athens in 529 because their teachings contradicted with Christian faith.
On July 9, 551, the