Review for the third hour exam, part three 62) What are Liesegang rings; how are they formed; and what do the look like? 63) Compare and contrast the geometric pattern of Liesegang rings with those produced by other reaction diffusion systems. 64) In the photograph of Liesegang rings on the course web page, can you figure out why rows of dots form in some places, in contrast to continuous lines formed in other places? How could you test whether your hypothesis is correct? Hint: The dark crystals precipitate wherever the concentration of silver ions multiplied by the concentration of bichromate ions gets higher than some threshold amount. {NOTE: should Turing, Meinhart and other hypothesizers of reaction-diffusion systems be paying more attention to concentrations of A multiplied by concentrations of B, rather than just their concentrations? Why or why not?} . 65) What are endothelial cells? Are they endodermal, despite what the name seems to suggest? Hint: no. In addition to endothelial cells, what are some other components of the walls of arteries and veins? 66) Compare the walls of arteries, veins, and capillaries. 67) Which of these statements is true? a) Blockage of arteries is caused by cholesterol sticking to the inside wall of blood vessels. b) Blockage is caused by thickening of artery walls. 68) What materials cause atherosclerosis? Where are they located? Are they inside the lumen? Are they surrounded by the endothelium? Or are they outside the endothelium (in the place where healthy arteries have only smooth muscle cells)? 69) What is an atheroma? Where is it located? What does it cause? 70) What is the role of macrophages in atherosclerosis? 71) All of our body's cells have a higher concentration of potassium ions in their cytoplasm as compared with the concentration of this ion in the surrounding fluid. This difference causes what? 72) The plasma membrane is normally more/less permeable to which of those two ions? If a cell became impermeable to potassium ions, what change would this produce? 73) When do oocytes become more permeable to sodium and calcium ions? 74) What function(s) are accomplished by those increases in ion permeabilities? In nerve axons? In oocytes? 75) Suppose that cancer cells have abnormal ion concentrations in their cytoplasm. How could this be used as the basis of diagnosis? As a basis for treatment? 76) Which kinds of differentiated cells have "resting potentials"? 77) What are the similarities between the fast block to polyspermy and the propagation of nerve impulses? Please include secretion of synaptic vesicles and part of the slow block to polyspermy? 78) Suggest how blocks to polyspermy could be used to prevent pregnancy. 79) Are nerves and muscles the only differentiated cell types in which the voltage of the cytoplasm is more negative than the voltage of the fluids outside the plasma membrane? 80) This voltage difference is caused by (Which ions? Potassium? Sodium?) being more than ten times more concentrated in the cytoplasm as compared with outside cells. Why is a positive voltage outside cells produced by positive ions of a certain element? (Hint: Potassium) being more concentrated inside of cells? ) (Hint:leakage) 81) What would happen if an oocyte suddenly became more permeable to sodium ions than to potassium ions? Does that ever actually happen? (Hint: yes; and this change in permeability serves what very important function?) 82) Why are such propagated changes in cytoplasmic voltage a better way to produce a change in cell behavior than simple diffusion of hormones or hormone-like molecules (hint: depolarization propagates much faster than simple diffusion). 83) Suppose that a a certain kind of cell crawls actively, and can detect differences and changes in the voltage difference between the inside and the outside of their plasma membranes. Describe two alternative sets of responses that could produce galvanotaxis (Hint: galvanotaxis is locomotion toward or away from increasing electric fields). Further hint: remember those two different ways of producing chemotaxis. What would the net result be if a cell turned randomly every time it detected an increase in the magnitude of an electric fields? *84) A more challenging question: Given that concentration of a chemical is a scalar variable, but electric voltage behaves like a vector, please try to invent more combinations of cell behaviors that could produce galvanotaxis, that depend on directionality of vector variables. *85) Another somewhat difficult question: How can cartilages elongate directionally unless the driving force is at least a vector, and perhaps a tensor variable? Would that mean that osmotic swelling cannot be the driving force for elongation of cartilages? (since osmotic pressure is a scalar variable) (Hint: why not?) *86) Remember the swimming ciliates, and how they back up when they hit something. Suggest how their movement (ciliary beating) might be explained as the result of propagated changes in ion permeability and trans-membrane voltages. Work out a mechanism by which you could get temporal chemotaxis using changes in ion permeability. Do the same for spatial chemotaxis.