The effect of increasing extracellular K+

Activity 1: What was the effect of increasing extracellular K+ (related to diffusion)? How was this different than the change you observed with extracellular Na+? Why might this be?
Activity 3: How did the action potential at R1 (or R2) change as you increased the stimulus voltage above the threshold voltage? How does this relate to the term “all-or-none”?
Activity 4: Why are fewer action potentials recorded at R2 when lidocaine is applied between R1 and R2? Why might you receive lidocaine at the dentist (rather than, say TTX)?
Activity 5: What was the measured absolute refractory period for this neuron? What “occurs” during this time?
Activity 7: Which was the fastest and which was the slowest of the fibers you compared?
What is the relationship between nerve size and conduction velocity?
What is your conclusion regarding conduction velocity and whether the nerve is myelinated or not?
Activity 8: What happened to the amount of neurotransmitter release when you switched from the control extracellular fluid to the extracellular fluid with no Ca++? Why?
Activity 9: Why was there no response at R2 when you apply a very weak stimulus to the sensory receptor? Is there any depolarization that occurs?

Sample Solution