1. The nervous system contains two general types of cells: neuroglia cells and
a. nerves.
b. cell bodies.
c. neurons.
d. nephrons.
2. The resting membrane potential of the neuron in this lab under the control conditions was _______ mV.
3. True or False: For most neurons, the concentration of Na+ and K+ ions inside and outside the cell are the primary factors that determine the resting membrane potential.
4. Explain why increasing the extracellular K+ causes the membrane potential to change to a less negative value.
5. Discuss the relative permeability of the membrane to Na+ and to K+ in a resting neuron.
6. Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential.
ACTIVITY 2: Receptor Potential
7. The “receiving end” of a sensory neuron is called the sensory receptor. It has proteins that can generate a signal called the _________ potential when the sensory neuron is stimulated.
8. Which of the following is not a sensory modality?
a. taste
b. smell
c. touch
d. height
9. The maximum amplitude of response of the Pacinian corpuscle to pressure in this simulation was ____ mV.
10. Sensory neurons have a resting membrane potential based on the efflux of potassium ions (as demonstrated in Activity 1.) What passive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle, and in the membrane of the free nerve ending?
11. What is meant by the term graded potential?
12. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle.
13. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the olfactory receptors.
14. What type of sensory receptor would likely respond to a green light?
ACTIVITY 3: The Action Potential: Threshold
15. In this lab simulation, what stimulus voltage first caused voltage to be seen at R1 and R2? _______ mV
16. True or False: A neuron must be polarized to the threshold voltage before an action potential is generated.
17. If the resting membrane potential of a neuron is -70mV and the threshold voltage of that neuron is -50 mV, then the neuron must be depolarized by a minimum of ______ mV before an action potential is generated.
a. 10mV
b. 15mV
c. 20mV
d. 30mV
18. Define the term threshold as it applies to an action potential.
19. What change in membrane potential (depolarization or hyperpolarization) triggers an action potential?
20. How did the action potential at R1 (or at R2) change as you increased the stimulus voltage above the threshold voltage?
21. An action potential is an “all-or-nothing” event. What does this mean?
ACTIVITY 4: The Action Potential: Importance of Voltage-Gated Na+ Channels
22. According to your lab manual, “voltage-gated” channels open when the cell membrane of the neuron ___________.
23. When Na+ ions flow through open channels into the neuron, then the membrane potential becomes
a. more negative
b. less negative
c. closer to, at, or above the threshold voltage
d. both b. and c.
24. True or False: When a voltage-gated Na+ channel is closed, then the Na+ ions actually flow in the opposite direction than if the channel is open.
25. What does TTX do to voltage-gated Na+ channels?
26. What does lidocaine do to voltage-gated Na+ channels? How does its effect differ from the effect of TTX?
27. Why are fewer action potentials recorded at R2 when TTX is applied between R1 and R2?
28. Why are fewer action potentials recorded at R2 when lidocaine is applied between R1 and R2?
29. Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in pain perception. Where should a dentist inject the lidocaine to block pain perception?
ACTIVITY 5: The Action Potential: Measuring Absolute and Relative Refractory Periods
30. According to your lab manual, voltage-gated Na+ channels inactivate (close) about _______ milliseconds after they open.
31. During the absolute refractory period, a neuron would need to be depolarized by _____ mV before another action potential could be generated.
a. 50 mV
b. 75 mV
c. 100 mV
d. Another action potential cannot be generated
32. True or False: In this lab simulation, when the interval between stimuli was 7.5 msec and the stimulus voltage was 60 mV, a second action potential was seen.
33. Define the absolute refractory period.
34. How did the threshold for the second action potential change as you further decreased the interval between the stimuli?
35. Why is it harder to generate a second action potential during the relative refractory period?
ACTIVITY 6: The Action Potential: Coding for Stimulus Intensity
36. In the previous activities, you should have noticed that the amplitude (height) of the action potential
a. is always the same.
b. is an all-or-none event.
c. depends on the intensity of the stimulus.
d. Both a. and b. are true.
37. True or False: It is important for the body to be able to determine the intensity of a stimulus.
38. In this lab simulation, when the stimulus voltage was 30 mV, the ISI was 62msec. This codes for an action potential frequency of _______ Hz.
39. Why does the frequency of action potentials increase when the stimulus intensity increases?
40. How does the threshold voltage change during the relative refractory period?
ACTIVITY 7: The Action Potential: Conduction Velocity
41. True or False: All of the axons in the human body conduct the nerve impulse (action potential) at the same velocity.
42. Which of these three axons was able to conduct the action potential the fastest?
a. The A fiber
b. The B fiber
c. The C fiber
d. All velocities were the same
43. In this simulation, the conduction velocity of the A fiber was ______ m/sec; the conduction velocity of the B fiber was ______ m/sec; the conduction velocity of the C fiber was ______ m/sec.
44. What is the effect of axon diameter on the conduction velocity?
45. What is the effect of the amount of myelination on conduction velocity?
46. Why did the time between stimulation and the action potential at R1 differ for each axon?
ACTIVITY 8: Chemical Synaptic Transmission and Neurotransmitter Release
47. The synapse is the location where the axon of one neuron communicates with
a. another neuron.
b. a muscle fiber.
c. a sensory receptor.
d. any or all of the above.
48. Neurotransmitter is released into the synaptic gap by a process called
a. secretion.
b. excretion.
c. exocytosis.
d. diffusion.
49. The name of the specific neurotransmitter released at a synapse between a motor neuron and a muscle cell is ____________.
50. When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of neurotransmitter per vesicle?
51. What happened to the amount of neurotransmitter released when you switched from the control extracellular fluid to the extracellular fluid with no Ca2+?
52. What happened to the amount of neurotransmitter released when you switched from the extracellular fluid with no Ca2+ to the extracellular fluid with low Ca2+?
ACTIVITY 9: The Action Potential…Putting It All Together
53. True or False: The amplitude of the depolarization that can result at the postsynaptic receptor is always the same.
54. In this simulation, when the sensory neuron membrane potential at the receptor was -40mV, the interneuron membrane potential at the “receiving end” was ______ mV.
55. In this simulation, with a “strong stimulus”, _____ sensory neuron vesicles were released from the axon terminal.
a. many, many
b. 15
c. 10d. 6
56. Describe what happened when you applied a very weak stimulus to the sensory receptor, i.e. was there an action potential? How many vesicles were released?
57. Describe what happened when you applied a moderate stimulus to the sensory receptor, i.e. was there an action potential? How many vesicles were released?
58. Identify the type of membrane potential (graded receptor potential or action potential) that occurred at R1, R2, R3, and R4 when you applied a moderate stimulus. (Compare/view the response to the stimulus.)
59. Describe what happened when you applied a strong stimulus to the sensory receptor. What type(s) of membrane potential were caused? Were the responses at R1 through R4 all the same?
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