EBME201 Exam2_2007_A

EBME201 Exam2_2007_A - 1) When using a voltage clamp on a...

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

View Full Document Right Arrow Icon
1) When using a voltage clamp on a section of an axon, what primary electrical parameter does the experimenter control?______ Voltage ________ (2 points) ______. Which electrical parameter is then directly measured by the experimenter?____ Current (2 points) _______________. Which parameter can then be calculated from the other electrical parameters you have measured or defined?__ Conductance or Resistance (2 points) __________. If you add a Na+ channel blocker to the extracellular solution, which of the above parameters would change? -Both current and conductance (resistance) would change (3points; 1.5 each) (9 points total) (Scott) 2) Why do action potentials generally start at the axon hillock? What is special about that part of the membrane? -It has a high density of voltage gated Na + channels (3points) (Scott) 3) Use the following diagram of the voltage during an action potential overlaid with traces showing the conductance of the membrane to K+ and to Na+ to answer the questions below What ion current is large at point A?_____ Na + (1 point) ________ Is it going into or out of the cell? __ Into (1 point) ____. What two forces are causing that ion to flow in that direction? -Both concentration gradient and electrical gradient (3 points; 1.5 each) (Scott) Why does the Na+ conductance decrease at B? -Inactivation gates of the voltage-gated Na + channels are closing (3 points) (Scott) Why does the K+ conductance increase at C? -Voltage gated K+ channels are opening (this happens at a slower rate than the voltage gated Na+ channels) (3points) A B C D
Background image of page 1

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

View Full DocumentRight Arrow Icon
-In order to get full credit, you needed to mention that the membrane depolarization results in opening of the voltage-gated K + channels. It was not sufficient to just state there was an increase in K + conductance due to membrane depolarization. (Scott) Why does the K+ conductance decrease at D? -The voltage is decreasing. Therefore, the voltage-gated K+ channels close again. (3 points) -In order to get full credit, you needed to mention that the membrane repolarization results in closing of voltage-gated K + channels. It was not sufficient to just state there was a decrease in K + conductance due to membrane repolarization. (Scott) 4) What would happen to the size of the action potential if you decreased the concentration of Na+ outside the cell? (Explain your answer). -By lowering the concentration outside the cell, the concentration gradient will be lower. Therefore, there will be less driving force and less Na + flowing in to depolarize the cell. The amplitude of the action potential will decrease because not as much Na + will come in before the Na + inactivation gates start closing. (3 points) -1/3 points was given if you stated that the size of the action potential would decrease without giving the correct explanation. -It is important to understand that the decrease in extracellular Na
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 10/13/2008 for the course EBME 201 taught by Professor Dawntaylor during the Spring '08 term at Case Western.

Page1 / 14

EBME201 Exam2_2007_A - 1) When using a voltage clamp on a...

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