Exam1ans. rev - PSL 431 First Hourly Exam A,B,C question...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
PSL 431 First Hourly Exam Fall 2006 Answers and explanations A,B,C question numbers 1, 21, 5 The Nernst potential for Cl - across a particular cell is +20mV. The measured membrane potential is 0mV (zero). Under these conditions therefore, Cl - A. is at equilibrium across the cell membrane. (Nernst is equilibrium, 0mV is not) B. is more concentrated outside the cell. (+ 20 mV is attracting the neg. charged ion, it must be more conc. inside ) C. has the same concentration on both sides of the cell. (in this case, the Nernst potential would be zero) *D. would tend to leave the cell. (yes, because the 0mV is less than the equil. potential, and so doesn't balance the concentration driving force going out ofthe cell ) E. has an electrical driving force out of the cell. (At 0mV there is no electrical driving force, there's no voltage) 2, 26, 12 The dynamics of Ca ++ ions in cardiac and smooth muscle are similar in that both A. use only an external source of Ca ++ . (all forms of muscle use internal Ca extensively) B. extensively utilize the IP3 second messenger system to release Ca ++ (only true of smooth muscle, cardiac uses Ca induced Ca++ release). *C. regulate the strength of contraction primarily by regulating intracellular Ca ++ (yes, this was emphasized for in both lectures 13 and 14 D. activate the actomyosin ATPase with the same Ca ++ binding proteins. (cardiac uses troponin/tropomyosin, smooth uses MLCK E. release Ca ++ from mitochondrial stores to activate actomyosin. (No type of muscle releases mitochondrial stores normally) 3, 27, 32 3A resting neuron is stimulated to threshold in the middle of the axon. Under these unusual conditions A. the action potential would not reach the synaptic terminal. *B. the action potential would propagate in both directions along the axon. (correct) C. the voltage-dependent Na+ channel would not open. D. the action potential would be propagated normally down the axon. E. No action potential would fire. (The only thing that is affected by stimulating the neuron in the middle is that there are now V- gated Na channels in the closed state on both sides, not inactivated on one side as usual. Thus, the AP can travel in both directions. Nothing else differs by stimulating in the middle) 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
PSL 431 First Hourly Exam Fall 2006 Answers and explanations A,B,C question numbers 4, 28, 33 The 'high salt hypothesis' for the effects of cystic fibrosis on the lung postulates that A. too much salt is absorbed from the airway surface liquid (ASL). (the high salt hypothesis is too little salt is absorbed) B. the main effect of mutant CFTR is to dysregulate the ENaC channel. (the ENaC channel plays an important role in low volume hypothesis C. too much water is taken up from the ASL. (again, this is true for the low volume hypothesis
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/03/2009 for the course PSL 431 taught by Professor Stephenson during the Spring '07 term at Michigan State University.

Page1 / 13

Exam1ans. rev - PSL 431 First Hourly Exam A,B,C question...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online