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Hypotension, also known as low blood pressure, is a cardiovascular condition characterized by abnormally reduced blood pressure. [1] Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood [2] and is indicated by two numbers, the systolic blood pressure (the top number) and the diastolic blood pressure (the bottom number), which are the ...
Low pressure baroreceptors have both circulatory and renal effects, which produce changes in hormone secretion. Stimulation of these receptors causes the atria to release atrial natriuretic peptide. This hormone acts on the kidneys to increase sodium excretion, which increases urine production and thereby leads to a decrease in blood pressure.
The drop in blood pressure may be sudden (vasovagal orthostatic hypotension), within 3 minutes (classic orthostatic hypotension) or gradual (delayed orthostatic hypotension). [4] It is defined as a fall in systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least
The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body. Exposure to pressure below this limit results in a rapid loss of consciousness, followed by a series of changes to cardiovascular and neurological functions, and ...
A low-pressure area is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the troposphere. [1] The formation process of a low-pressure area is known as cyclogenesis. [2]
In deserts, the lack of ground and plant moisture, that would normally provide evaporative cooling, can lead to intense, rapid solar heating of the lower layers of air. The hot air is less dense than surrounding cooler air. That, combined with the rise of the hot air, results in a low pressure area called a thermal low. [1]
Local venous pressure falls to -5 at the apexes and rises to +15 mmHg at the bases, again for the erect lung. Pulmonary blood pressure is typically in the range 25–10 mmHg with a mean pressure of 15 mmHg. Regional arterial blood pressure is typically in the range 5 mmHg near the apex of the lung to 25 mmHg at the base.
The whole of the venous system, bar the post-capillary venules is a large volume, low pressure system. [9] The venous system is often asymmetric, and whilst the main veins hold a relatively constant position, unlike arteries, the precise location of veins varies among individuals. [5] [7] Positions of venae cavae and vessels of the pulmonary ...