Well, helloooo, this is after she was being dehydrated for two weeks. The brain is 80% water, so naturally during the extended process of dehydration, it would lose water and weight. So the weight of her brain doesn't mean much.
Boy, you aren't the brightest bulb in the pack, are you.
"Well, helloooo, this is after she was being dehydrated for two weeks. The brain is 80% water, so naturally during the extended process of dehydration, it would lose water and weight."
Mild dehydration... The autonomic nervous system causes the vessels in the brain to ***become dilated to keep more blood in the brain*** while vessels in the rest of our body become constricted to keep our blood pressure up. The pressure from the dilated vessels puts pressure on the
brain (because it's encased in the skull) and we get a headache.
Luckily, there are many compensatory mechanisms in place to protect the brain above all other body parts. Groups of cells in the aorta and in the hypothalamus work to sense the fluid volume and the osmolarity (how concentrated or dilute the blood is) and orchestrate hormonal signals to ***compensate for the loss of water.***
You can find this information in a basic physiology book ( one by Lauralee Sherwood) and many neuroscience texts in your library.
http://www.madsci.org/posts/archives/sep99/938556195.Ns.r.html
Dehydration...
When we become hypovolemic several things happen. First our heart speeds up. It pumps less volume per beat (stroke volume) but beats more often to compensate for this and maintain cardiac output (the number of liters of blood pumped per minute). Second the blood levels of catecholamines (epinephrine, norepinephrine and dopamine) go up. ***This causes blood vessels in the critical organs such as heart, brain, liver and kidneys to dilate*** and the vessels in the less critical areas (gut, muscles) to constrict. Changes in the output from our sympathetic nervous system reinforce this. ***The net effect is reduced blood flow to the muscles and gut and more to the brain etc.*** Thirdly, receptors that measure our blood pressure, our sodium level, etc. tell the brain to increase our volume, this kicks in our thirst mechanism. Fourthly, the atria of our heart, since they are smaller in diameter reduce their production of ANP, a peptide hormone that stimulates the kidneys to make urine. Thus the kidneys reduce their secretion of sodium and urine.
Robert S. Joseph, RPh, MD, FCCP
Board Certified Internal Medicine and Critical Care Medicine
In other words, the brain weight loss would be minimal. Please feel free to select a bulb.