vasodilation

Examples of vasodilation in the following topics:

• Short-Term Chemical Control

  • Blood pressure is controlled chemically through dilation or constriction of the blood vessels by vasodilators and vasocontrictors.
  • The primary function of vasodilation is to increase blood flow in the body to tissues that need it most.
  • Localized tissues increase blood flow by several methods, including the release of vasodilators, primarily adenosine, into the local interstitial fluid, which diffuses to capillary beds provoking local vasodilation.
  • Some physiologists have suggested the lack of oxygen itself causes capillary beds to vasodilate by the smooth muscle hypoxia of the vessels in the region.
  • As with vasoconstriction, vasodilation is modulated by calcium ion concentration and myosin phosphorylation within vascular smooth muscle cells.

• Local Regulation of Blood Flow

  • Blood flow is regulated by vasoconstriction or vasodilation of smooth muscle fibers in the walls of blood vessels, typically arterioles.
  • Local responses to stretch, carbon dioxide, pH, and oxygen also influence smooth muscle tone and thus vasoconstriction and vasodilation.
  • Generally, stretch and high oxygen tension increase tone, and carbon dioxide and low pH promote vasodilation.
  • Pulmonary arterioles are a noteworthy exception as they vasodilate in high oxygen.
  • Brain arterioles are particularly sensitive to pH, with reduced pH promoting vasodilation.

• Blood Flow in the Skin

  • These muscles are under the control of the sympathetic nervous system and provide an efficient means of thermoregulation through vasoconstriction and vasodilation.
  • When vasodilated, blood flow through the skin is increased, meaning more core heat can be lost through radiation.

• Distribution of Blood

  • The process is the opposite of vasodilation, the widening of blood vessels.
  • Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large veins, large arteries, and smaller arterioles.
  • Substances that cause vasodilation are termed vasodilators.

• Vascular Spasm

  • The process is the opposite of vasodilation, the dilation and expansion of blood vessels.
  • During inflammation, vasodilation occur, along with increased vascular permeability and leukocyte chemotaxis, ending the spasm of vasoconstriction and hemostasis as wound healing begins.

• Inflammation

  • They are vasodilation, increased vascular permeability, and migration of leukocytes to the effected tissues.
  • Then the blood vessels will expand to undergo vasodilation from the stimulus of the vasoactive inflammatory mediator, which increases flow of blood to the area, and causes slowing and stasis of red blood cells, which can be involved in the clotting response needed to stop bleeding in the case of injuries.
  • This vasodilation is the reason for the redness, heat, and pain, associated with inflammation.

• Heat Conservation and Dissipation

  • For example, vasodilation brings more blood and heat to the body surface, facilitating radiation and evaporative heat loss, which helps to cool the body.
  • In endotherms, the circulatory system is used to help maintain body temperature, either by vasodilation or vasoconstriction.

• Introduction to Blood Flow, Pressure, and Resistance

  • Arterioles in particular are able to rapidly alter resistance by altering their radius through vasodilation or vasoconstriction.
  • Blood pressure can be modulated through altering cardiac activity, vasoconstriction, or vasodilation.

• Types of Shock

  • Septic shock is the most common cause of distributive shock and is caused by an overwhelming systemic infection that cannot be cleared by the immune system, resulting in vasodilation and hypotension.
  • Anaphylactic shock is caused by a severe reaction to an allergen, leading to the release of histamine that causes widespread vasodilation and hypotension.

• Adrenergic Neurons and Receptors

  • Adrenaline (epinephrine) reacts with both α- and β-adrenoceptors, causing vasoconstriction and vasodilation, respectively.
  • Although α receptors are less sensitive to epinephrine, when activated, they override the vasodilation mediated by β-adrenoceptors.
  • At lower levels of circulating epinephrine, β-adrenoceptor stimulation dominates, producing an overall vasodilation.