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The underlying mechanism involves the nervous system slowing the heart rate and dilating blood vessels, resulting in low blood pressure and thus not enough blood flow to the brain. [2] Diagnosis is based on the symptoms after ruling out other possible causes. [3] Recovery from a reflex syncope episode happens without specific treatment. [2]
Low blood pressure and a fast heart rate after the event may indicate blood loss or dehydration, while low blood oxygen levels may be seen following the event in those with pulmonary embolism. [1] Routine broad panel laboratory testing detects abnormalities in <2–3% of results and is therefore not recommended.
Lightheadedness is a common and typically unpleasant sensation of dizziness [1] or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may feel as though their head is weightless.
Vertebrobasilar insufficiency (VBI) describes a temporary set of symptoms due to decreased blood flow in the posterior circulation of the brain.The posterior circulation supplies the medulla, pons, midbrain, cerebellum and (in 70-80% of people) supplies the posterior cerebellar artery to the thalamus and occipital cortex. [1]
An experiment from Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus. Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (Latin, 'An Anatomical Exercise on the Motion of the Heart and Blood in Living Beings'), commonly called De Motu Cordis, is the best-known work of the physician William Harvey, which was first published in 1628 and established the ...
Dizziness is a common medical complaint, affecting 20–30% of persons. [4] Dizziness is broken down into four main subtypes: vertigo (~25–50%), disequilibrium (less than ~15%), presyncope (less than ~15%), and nonspecific dizziness (~10%). [5] Vertigo is the sensation of spinning or having one's surroundings spin about them. Many people find ...
Pulmonary (lung) circulation undergoes hypoxic vasoconstriction, which is a unique mechanism of local regulation in that the blood vessels in this organ react to hypoxemia, or low levels of dissolved oxygen in blood, in the opposite way as the rest of the body. While tissues and organs tend to increase blood flow by vasodilating in response to ...
The blood volume determines the mean pressure throughout the system, in particular in the venous side where most of the blood is held. The low-pressure baroreceptors have both circulatory and renal effects; they produce changes in hormone secretion, resulting in profound effects on the retention of salt and water ; they also influence intake of ...