Search found 32 matches

by xand_3r
Sat Jul 04, 2009 11:01 pm
Forum: Physiology
Topic: blood brain barrier
Replies: 2
Views: 13510

The answer to your question is yes. Normally, the b-b barrier cannot be passed by the immune cells. When infection occurs such as meningitis or encephalitis, because of the inflammation caused by bacterial toxins, destroyed neurons and endogenous substances, the endothelial cells become more permeab...
by xand_3r
Sat Jun 02, 2007 10:46 pm
Forum: Physiology
Topic: simple diffusion and skin cells
Replies: 5
Views: 9977

About 1% of respiration occurs through skin. This is an extremely low value if you take in consideration that the skin is almost always in contact with air and it has a very large surface. Skin is impermeable to water and solutes but liposoluble substances (including gases) can pass.
by xand_3r
Thu Mar 08, 2007 10:40 am
Forum: Physiology
Topic: Difference in Phylums?
Replies: 4
Views: 7209

Other differences include blood composition : annelids have free hemoglobin in their blood, arthropods don't have any pigment in their blood since they have tracheal respiration and the others have hemocyanine as respiratory pigment (also circulating free in the blood).
by xand_3r
Tue Mar 06, 2007 2:16 pm
Forum: Physiology
Topic: urea
Replies: 4
Views: 5802

urea and uric acid are two very different things. Urea is a product of protein catabolism while uric acid is a product of nitrous bases catabolism. So different formulas different origin. Similar name.
by xand_3r
Mon Mar 05, 2007 5:11 pm
Forum: Human Biology
Topic: Antibodies in breast milk
Replies: 16
Views: 12259

Ph in the baby's stomach is higher than in the adult stomach (about 4.5-5 instead of the normal 1.5-3). Lower pH is needed for pepsin to be activated, so at a pH of 4.5-5 pepsin has little activity, so many proteins can escape digestion.
by xand_3r
Mon Mar 05, 2007 4:58 pm
Forum: Physiology
Topic: Basophils vs. Mastocytes
Replies: 4
Views: 7586

Well, in fact there are two different theories, one that states that mast cells are derived from basophyls and other that states that mast cells are derived from mastoblasts from the bone marrow (mastoblast->promast cell->mast cell)
by xand_3r
Mon Mar 05, 2007 4:53 pm
Forum: General Discussion
Topic: diabetes
Replies: 5
Views: 4951

Normally, some of the glucose passes away along with the glomerular ultrafiltrate in the proximal urinifer tubule . Then, all the glucose is actively reabsorbed so the final urine has no glucose. If the blood concentration of glucose is higher than a certain value (about 300 mg/dl but I'm not sure),...
by xand_3r
Fri Aug 04, 2006 5:43 pm
Forum: Ecology
Topic: Did death evolve?
Replies: 114
Views: 104632

Cancer cells have an altered cell cycle, having rapid division and lacking the mechanisms for apoptosys so we could say that they're immortal. Anyway, if an organism lives long enough, even without an ageing mechanism it will eventually die because of negative mutations. Mitochondrion DNA cannot be ...
by xand_3r
Wed Aug 02, 2006 8:46 am
Forum: Genetics
Topic: Genetics of Marfan Syndrome
Replies: 3
Views: 3211

The Marfan sindrome is caused by an autosomal dominant allele. The location of the defective gene seems to be the 15th chromosome. Being a dominant allele, it means that the child might be affected only if one of the parents has the disease (meaning that it has the gene). If one of the parents is mo...
by xand_3r
Tue Aug 01, 2006 1:53 pm
Forum: General Discussion
Topic: mcq
Replies: 8
Views: 4169

Do you refer to testing or demonstrating?
by xand_3r
Tue Aug 01, 2006 1:44 pm
Forum: Botany Discussion
Topic: 3 questions
Replies: 3
Views: 2628

A way for stopping an ion either from entering or from exiting a cell are voltage dependent channels (they open and close only at certain values of the cell potential). So equilibrum can't occur since at a certain voltage value the channel closes, even if the concentration gradients aren't met.
by xand_3r
Tue Aug 01, 2006 1:40 pm
Forum: Botany Discussion
Topic: 3 questions
Replies: 3
Views: 2628

For #3: Usually equilibrum never occurs, since equilibrum is equivalent with maximum entropy (so maximum disorder), and organisms are ordoned systems. The gradients of concentration are maintained through active transport systems. For example, the gradient for Na and K is maintained by the Na/K pump...