Chsc 2p09 Quiz Two Notes
Activity 1: The Resting Membrane Potential
Pre-lab Quiz Results
1. What is the approximate concentration of K+ inside a typical cell (intracellular concentration)?
a. 150 mM
2. What is the approximate concentration of K+ outside a cell (extracellular concentration)?
b. 5 mM
3. What is the approximate concentration of Na+ inside a cell (intracellular concentration)?
b. 5 mM
4. What is the approximate concentration of Na+ outside a cell (extracellular concentration)?
a. 150 mM
Experiment Results
1. What is the polarity of the resting membrane potential (voltage)?
b. negative
2. What does it mean that the voltage just inside the membrane is negative?
b. There are more negative charges than positive charges just inside the membrane.
3. The membrane of most cells, including neurons, contains passive, open, K+ leak channels. Given the normal K+ concentrations and the resultant concentration gradient, which direction would K+ be expected to move (diffuse) through these leak channels?
b. out of the cell
4. What effect does increasing extracellular K+ have on the net diffusion of K+ out of the cell?
b. It decreases the net diffusion of K+ .
5. Which way would Na+ move across the membrane if there were open Na+ channels?
a. Na+ would diffuse into the cell.
6. The membrane has open K+ channels, and changing extracellular K+ concentration results in a change in membrane potential. Changing the extracellular Na+ concentration does not significantly change the membrane potential. What do your results suggest about the number or state (open or closed) of Na+ channels in the resting membrane of a neuron?
b. Na+ channels are mostly closed.
Pre-lab Quiz Results
1. A negative membrane potential was recorded when the tip of the microelectrode was
d. both inside the cell body and inside the axon.
2. Which of the following caused a change in membrane potential from -70 to -40 in the cell body?
a. an increase in extracellular K+
3. Which of the following
Pre-lab Quiz Results
1. What is the approximate concentration of K+ inside a typical cell (intracellular concentration)?
a. 150 mM
2. What is the approximate concentration of K+ outside a cell (extracellular concentration)?
b. 5 mM
3. What is the approximate concentration of Na+ inside a cell (intracellular concentration)?
b. 5 mM
4. What is the approximate concentration of Na+ outside a cell (extracellular concentration)?
a. 150 mM
Experiment Results
1. What is the polarity of the resting membrane potential (voltage)?
b. negative
2. What does it mean that the voltage just inside the membrane is negative?
b. There are more negative charges than positive charges just inside the membrane.
3. The membrane of most cells, including neurons, contains passive, open, K+ leak channels. Given the normal K+ concentrations and the resultant concentration gradient, which direction would K+ be expected to move (diffuse) through these leak channels?
b. out of the cell
4. What effect does increasing extracellular K+ have on the net diffusion of K+ out of the cell?
b. It decreases the net diffusion of K+ .
5. Which way would Na+ move across the membrane if there were open Na+ channels?
a. Na+ would diffuse into the cell.
6. The membrane has open K+ channels, and changing extracellular K+ concentration results in a change in membrane potential. Changing the extracellular Na+ concentration does not significantly change the membrane potential. What do your results suggest about the number or state (open or closed) of Na+ channels in the resting membrane of a neuron?
b. Na+ channels are mostly closed.
Pre-lab Quiz Results
1. A negative membrane potential was recorded when the tip of the microelectrode was
d. both inside the cell body and inside the axon.
2. Which of the following caused a change in membrane potential from -70 to -40 in the cell body?
a. an increase in extracellular K+
3. Which of the following