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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. ATP is used as a form of energy to increase this pressure to heat the body. Once homeostasis is restored, the blood pressure and ATP production regulates.
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).
Further, multiple species of snakes have been shown to constrict with pressures higher than those needed to induce cardiac arrest. [7] [8] [9] In conjunction with observations of oral and nasal hemorrhaging in prey, constriction pressures are also thought to interfere with neural processing by forcing blood towards the brain.
While a different cause, this has very similar symptoms, namely the immunological reaction involving release of inflammatory mediators. Inhalation of allergens in sensitized subjects develops into bronchoconstriction within 10 minutes, reaches a maximum within 30 minutes, and usually resolves itself within one to three hours.
Dilation and constriction of the pupil. Pupillary response is a physiological response that varies the size of the pupil, via the optic and oculomotor cranial nerve.. A constriction response (), [1] is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/opioids or anti-hypertension medications.
A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning.
During Xenopus gastrulation, bottle cells are located in the dorsal marginal zone and apically constrict inwards to initiate involution of the blastopore. In these cells, apical constriction occurs when actomyosin contractility folds the cell membrane to reduce the apical surface area.
Cerebral blood vessels are able to change the flow of blood through them by altering their diameters in a process called cerebral autoregulation; they constrict when systemic blood pressure is raised and dilate when it is lowered. [15] Arterioles also constrict and dilate in response to different chemical concentrations.