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It is part of a body negative feedback loop in which the body tries to restore homeostasis (maintain constant internal environment). [citation needed] For example, vasoconstriction is a hypothermic preventative in which the blood vessels constrict and blood must move at a higher pressure to actively prevent a hypoxic reaction.
As more chemicals are released more platelets stick and release their chemicals; creating a platelet plug and continuing the process in a positive feedback loop. Platelets alone are responsible for stopping the bleeding of unnoticed wear and tear of our skin on a daily basis. This is referred to as primary hemostasis. [5] [7]
This is known as a closed-loop obstruction because there exists an isolated ("closed") loop of bowel. Acute volvulus often requires immediate surgical intervention to untwist the affected segment of bowel and possibly resect any unsalvageable portion. [11] Volvulus occurs most frequently in middle-aged and elderly men. [11]
Venous return (VR) is the flow of blood back to the heart. Under steady-state conditions, venous return must equal cardiac output (Q), when averaged over time because the cardiovascular system is essentially a closed loop. Otherwise, blood would accumulate in either the systemic or pulmonary circulations.
Constriction is a method used by several snake species to kill or subdue their prey. Although some species of venomous and mildly venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. [ 1 ]
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Hypoxic pulmonary vasoconstriction (HPV), also known as the Euler-Liljestrand mechanism, is a physiological phenomenon in which small pulmonary arteries constrict in the presence of alveolar hypoxia (low oxygen levels).
The dilation, then quick constriction, of this blood vessel may be a type of self-defense for the brain. [ citation needed ] This inflow of blood cannot be cleared as quickly as it is coming in during the cold-stimulus headache, so the blood flow could raise the pressure inside the skull and induce pain that way.