Chsc 2p09 Quiz Two Notes

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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 has the most negative voltage?
c. between the inside of the axon and the outside of the axon with control K+ ECF

Activity 2: Receptor Potential
Pre-lab Quiz Results
1. Assuming that the resting potential of a sensory neuron is -70 mV, which of the following represents a depolarization? c. a change to -60 mV
2. Which of the following is a sensory modality (type of sense)? e. all of the above (touch, smell, sight, pain)
3. Which of the following is a sensory stimulus?
d. all of the above (pressure, chemical odorants, light)
4. Which of the following is true of the response of a sensory neuron to the appropriate sensory stimulus? c. both a and b (it can be called a receptor potential and it is a graded potential, it is a change in the resting membrane potential)

Experiment Results
1. Why didn't the Pacinian corpuscle respond to high-intensity light? b. Light-transducing proteins are not present in the Pacinian corpuscle. 2. Judging from these results, does light have a smell?

b. no
3. Why did the free nerve ending respond to several different modalities? c. The sensory end of this nerve is less specialized.

Post-lab Quiz Results
1. A very intense stimulus can sometimes stimulate sensory neurons that have evolved for a different modality. Thus, with a blow to the eye, one "sees stars." In this example the photoreceptors in the eye are responding to c. intense pressure.

2. Olfactory receptor neurons respond to low concentrations of chemical odorants because there are membrane proteins in the receptor ending of this sensory neuron that b. can bind and respond to the specific odorant.

3. The sequence of events starting with a sensory stimulus and ending with a change in membrane potential is called c. sensory transduction.
4. Starting at a resting membrane potential of -70 mV, a change to which of the following represents the largest receptor potential? d. a change to -50 mV

Activity 3: The Action Potential: Threshold
Pre-lab Quiz Results
1. Axons are
d....
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