Raynaud's disease results in brief periods of vasospasms. this disease affects blood supply to fingers and toes. it is also know
n to affect blood flow to lips, ears, nose and nipples. during what is called as "raynaud's attacks", the skin may turn white and then blue for a short time. which of these best describes why these symptoms occur?
The answer is excessive narrowing of blood vessels.
When exposed to the cold, our body tries to reduce its heat loss by tightening the arterioles under the skin (vasoconstriction). This mechanism increases the flow of blood into the deep veins and allows the body to maintain its internal temperature.
In people with Raynaud's disease, this reaction is excessive: the nerves that control the tightening of arterioles are hypersensitive and cause spasm, rather than normal vasoconstriction. When the spasm stops, the arterioles dilate again, restoring blood circulation.
Exocytosis is the process by which cells move materials from within the cell into the extracellular fluid. Exocytosis occurs when a vesicle fuses with the plasma membrane, allowing its contents to be released outside the cell. ... Carbon dioxide and water are removed from these cells via exocytosis.
Knowledge of the relationship between the size (volume) of cells and their surface area helps explain the process of diffusion. Agar blocks and cells with the largest surface area to volume ratio (the smaller cubes) have the highest diffusion rates.
It is intercepted first by the atmosphere, a small part of the sun's energy is directly absorbed, particularly by certain gases such as ozone and water vapor. during the day the sun shines through tha atmosphere <span> </span>
